Class 8

AP State Syllabus AP Board 8th Class Physical Science Solutions Chapter 11 Some Natural Phenomena Textbook Questions and Answers.

AP State Syllabus 8th Class Physical Science Solutions 11th Lesson Some Natural Phenomena

8th Class Physical Science 11th Lesson Some Natural Phenomena Textbook Questions and Answers

Improve Your Learning

Question 1.
Which of the following cannot be charged easily by friction?
A) A Plastic scale
B) A copper rod
C) An inflated balloon
D) A Woollen cloth
E) Piece of wood
Answer:
(B) A copper rod

Question 2.
When a glass rod is rubbed with a piece of silk cloth the rod
A) and the cloth both acquire positive charge.
B) becomes positively charged while cloth has a negative charge.
C) and the cloth both acquire negative charge.
D) becomes negatively charged while cloth has a positive charge.
Answer:
(B) becomes positively charged while cloth has a negative charge.

Question 3.
Identify ‘True’ or ‘False’ sentences among the following:
A) Like charges attract each other. (T/F)
B) A charged glass rod attract a charged plastic straw. (T/F)
C) Lightning conductor cannot protect a building from lightning. (T/F)
D) Earthquakes can be predicted in advance. (T/F)
Answer:
A) False
B) True
C) False
D) False

Question 4.
Sometimes, a crackling sound is heard while taking off sweater during winter. Explain.
Answer:
Charge is developed on the sweater because of friction. We can observe discharge of the charge while taking off the sweater which produce the crackling sound.

Question 5.
Explain why a charged body loses its charge if we touch it with our hand.
Answer:
The reason is that the charged object lose charge to the earth through our body that means it is transferred its charge to earth. The process of transferring of charge from a charged object to the earth is called earthing.

Question 6.
Name the scale on which the destructive energy of an earthquake is measured. An earthquake measures 3 on this scale. Would it be recorded by a seismograph? Is it likely to cause much damage?
Answer:
The destructive energy of earthquake is measured in richter scale. Yes, it would be recorded by seismograph when earthquake measures 3 on the richter scale. It does not cause any damage to human life, generally we unable to felt its effect.

Question 7.
Suggest three measures to protect ourselves from lightning.
Answer:
Precautions to be taken to protect ourselves from lightning.

1. Staying in a house or building of low height.
2. If we are travelling in a bus or car, then we are safe inside the car or bus provided doors and windows are closed.
3. If we are in a forest taking shelter under shorter trees than taller trees is a good idea during the thunder storm.

Question 8.
Explain why a charged balloon is repelled by another charged balloon whereas an uncharged balloon is attracted by a charged balloon?
Answer:
A charged balloon is repelled by another charged balloon having same type of charge because both are having same kind of charges and like charges repel each other. Whereas an uncharged balloon attracted by a charged balloon because charged balloon induces opposite charge on uncharged balloon. We already know unlike charges attract each other. So the uncharged balloon is attracted by a charged balloon.

Question 9.
List three states in India where earthquakes are more likely to occur?
Answer:
The three states are

1. Jammu & Kashmir State (Mainly Kashmir)
2. Whole north east states like Tripura, Manipur, etc.
3. Rajasthan.

Question 10.
Does your habitation lie in earthquake prone area? Explain.
Answer:
Yes, my habitation lie in earthquake prone area because 1 am living in delta region of Krishna which is placed in seismic zone III. So it has chances of possibility of earthquake. (If the answering person is not living in Chittoor, YSR Kadapa, Nellore districts and Krishna and Godavari delta region then the answer is No.)

Question 11.
Which place in Andhra Pradesh experiences earthquakes most of the time?
Answer:
Badrachalam and Kothagudem are the places where there is a possibility of earthquake most of the time. Chittoor, Kadapa, Nellore and Krishna and Godavari delta region also have greater possibility of earthquake because they lie in zone-111.

Question 12.
When does a piece of matter have a “charge?”
Answer:
When a piece of matter rubbed with another piece of matter, the piece of matter acquire charge due to friction.
E.g.: Rub the refill vigorously with a piece of polythene and if we bring piece of paper that can be attracted by refill due to development of charge.

Question 13.
What happens if two objects having same charge brought close to each other? What happens if two objects having different charges are brought close? Can you give an example for this.
Answer:
Two objects having same charge repel each other and two objects having different charge attract each other.
E.g. A balloon rubbed with woollen cloth repelled by another balloon rubbed with woollen cloth because both will acquire same type of charge.
A balloon rubbed with a woollen cloth attracted by a refill rubbed with a polythene sheet because both will acquire different type of charge.

Question 14.
Give two examples of effects in your daily life caused by transfer of charges.
Answer:
Two examples in daily life:

1. Earthing
2. Lightning

Question 15.
Inflate two balloons and rub both of them with a cloth first and then with different material. Will they attract each other in both cases?
Answer:
No, they will not attract each other. Both will repel each other. The reason is both ballons rubbed with same material acquired same charge in the both the cases.

Question 16.
Which country in the world is frequently affected by earthquakes? Collect the information and photographs on the recent earthquake in Japan.
Answer:
The country in the world which frequently affected by earthquakes is Japan. Pictures of earthquake affected areas in Japan in 2012.
Photographs of earthquake:

Information about earthquake:

1. Lot of people killed due to earthquake.
2. Lot of people killed not only due to earthquake but tsunami caused by earthquake.
3. Lot of property loss took place.
4. Most of the people in Japan lost their jobs and livinghood.
5. They suffered emotionally also by losing their relatives, parents and children.
6. Lot of effect felt on their economy.
7. It effected the tourism of Japan.

Question 17.
Find out if there is an organization in your area which provides relief to those suffering from natural disaster. Enquire about the type of help they render to the victims of earthquake. Prepare a brief report on the problems of the earthquake victims.
Answer:
In India National Disaster Force provides relief for disaster victims.
Problems of earthquake victims:

1. Death: Many times, the people who support a family socially and economically dies. This causes most of the other members of the family to either fight their way through, or restart their lives from the bottom of the food chain.
2. Destroyed Structures: If the members of the family survive, then they could still be short of a home. The earthquake would have caused the destruction of their house and because of that, they would be left homeless.
3. No food or water: In the aftermath of an earthquake, people see whether all the pipelines, roads, etc. are in good shape or order. If the pipes are broken, then water scarcity begins. If the roads are broken, then food supplies cannot be transported, later causing problems in food scarcity.
4. Electricity : With inadequate supply of electricity, the debris and rubble will take a lot of time and if people are under it then they may die before the rubble is removed.
5. Illnesses: After the destruction of many buildings, the sewer pipes will also break and open, causing spread of disease everywhere.

Help render by relief organisation:

1. They minimize the death of people.
2. They provide drinking water and food for victims.
3. They provide shelter for earthquake victims.
4. They provide medical facility for earthquake victims.

Question 18.
How do you relate the energy release during the collision of fault lines during earthquake to the atmospheric variation on the surface of the earth?
Answer:
An earthquake effects the atmosphere by creating amounts of debris and dust which will add to the air that we breathe. Earthquakes can also trigger volcanoes which will release tonnes of ashes and other debris into the atmosphere. This can sometime cause the blocking out of the sun, air pollution and are increased amount of carbon in the air.

Question 19.
Describe with the help of a diagram an instrument which can be used to detect a charged body.
Answer:
The instrument used to detect a charged body is electroscope.
Description of Electroscope:
Take an empty jam bottle. Take a piece of cardboard slightly bigger in size than the mouth of the bottle. Pierce a hole in it, so that a metal paper clip could be inserted. Open out paper clip as shown in the figure. Cut two strips of aluminium foil about 4 x 1 cm each and hang them on the paper clip.

Insert the paper clip having the strips of aluminium foil into the cardboard lid so that it is perpendicular to it. This entire device works as a electroscope.
Procedure to detect a charged body ,by using a electroscope:
Charge a refill and make it touch the end of the paper clip. The aluminium foils move away from each other the reason that the strips of aluminium foil receive the same charge from the charged body through the paper clip and strips carrying similar charges repel each other and hence they move apart. This proves electroscope is useful in detecting a charged body.

Question 20.
Colour seismic zones in India out line map.
Answer:

Question 21.
Prepare a model of seismograph.
Answer:
Preparation of model:

Take a pendulum and which is attached to support. This acts as vibrating system. A pen is attached to this vibrating system. Place a rotating drum covered with a paper just below the pen. When earthquake occurs the pen records the seismic waves on a paper which move under it.

Question 22.
How do you appreciate the efforts of scientists to develop an instrument to assess the intensity and source of earthquake?
Answer:
The efforts of scientists to develop an instrument to assess the intensity and source of earthquake is thoroughly appreciated because they provide assessment of earthquake and what are the rescue measurements to be taken by government and private organizations and also provide preventive measurements that would be taken when earthquake occurs. So these scientists providing life for people and their services are thoroughly appreciated.

Question 23.
Suppose you are outside your home and an earthquake occurs. What precautions would you take to protect yourself?
Answer:

1. I find a clear spot, away from buildings, trees and over head powerlines and I drop to the ground.
2. If I am in a car or bus, I do not come out and I ask the driver to drive slowly to a clear spot. I do not come out of the car or bus till the tremors stop.

Question 24.
The weather department has predicted that a thunder storm is likely to occur at on a certain day. Suppose you have to go out on that day. Would you carry an umbrella? Explain.
Answer:
No, I would not carry umbrella during thunderstorm because the metallic rod attached to the umbrella attracts the charge developed in thunderstorm and charge may carry through umbrella and possibility of electric shock. So it is not a good idea to carry umbrella during lightning.

Question 25.
If earthquake occurs in your area what will you do?
Answer:

1. I will protect myself by covering head with helmet or cushion and hide in a safe place, such as under table.
2. I will not run outside because roof tiles and glass may fall on me.
3. Major after shocks can come after smallest earthquake so I calmly extinguish any nearby flames.
4. Earthquake can wrap buildings, especially apartment buildings making it impossible to open doors and escape. So I open doors and windows to secure an escape route.
5. I will be careful with broken glass.
6. Once I come outside I will not return to house.
7. I will avoid phone calls.

Question 26.
What are the measures you would take in your house when an earthquake occurs?
Answer:

1. I would take shelter under a table and stay there till the shaking stops.
2. I would stay away from tall and heavy objects that may fall on me.
3. If I would be in the bed then I would not get up and I protect my head with a pillow.

8th Class Physical Science 11th Lesson Some Natural Phenomena Activities

Activity – 1

Question 1.
Effect of rubbing:

Take a used ball-pen refill and bring it near small pieces of paper.
The refill should be close enough but not touch the pieces of paper.
a) Check what happens to the paper pieces?
Answer:
They remain in the same position.
Now, rub the refill vigorously with a piece of polythene. Bring it close to small pieces of paper.

b) What is your observation. Take care that the rubbed end is not touched by your hand or with a metallic object.
Answer:
My observation is paper piece is attracted towards refill.
Now, take a comb and move it through dry hair a few times. Take the comb near small pieces of paper and check what happen.
The papers are attracted by comb.
Take an inflated balloon and rub it against your clothes. Bring the balloon close to small pieces of paper.
The paper pieces are attracted by balloon.
Take a drinking straw and rub it against a smooth wall or against your cloths, then bring it near pieces of paper.

c) What do you observe?
Answer:
The papers are not attracted by drinking straw.

d) Are they able to attract bits of paper after being rubbed?
Answer:
No, they are not attract bits of paper.
Repeat the activity by rubbing each one of the above mentioned objects (refill, comb, drinking straw, balloon) and use small pieces of dry leaf, husk, etc. as testing materials. Record your observation in table.

e) What can we infer from the above activity?
Answer:
When you rub material some material tend to attract pieces of paper.

f) Do objects like refill or comb attract pieces or paper only after rubbing?
Answer:
Yes, they attract pieces of paper only after rubbing.

g) Do all objects show this property?
Answer:
No, all the objects does not show this property.

h) Can we rub a comb against our palm and make it attract the paper bits?
Answer:
Yes, the paper bits are attracted to the palm due to friction charge is developed on the hand.

Lab Activity

Conduct an experiment of find the effects of charged bodies which have been rubbed by different materials.
Aim: To find effects of charged bodies which have been rubbed by different materials.
Materials required: A ball pen refill, a balloon, a comb, an eraser, a steel spoon, polythene sheet, plain paper, woollen cloth, etc.
Procedure:
Rub the above objects against materials listed in table. In each case, bring the rubbed object near small pieces of paper and note whether they attract pieces of paper or not. Record your observations in table by writing ‘yes’ or ‘no’.

a) What do you conclude from above table?
Answer:
Some objects like refill, comb when rubbed with specific materials able to attract light objects like bits of paper. But some objects like steel spoon do not attract pieces of paper even after rubbing.

b) Why don’t some materials attract pieces of paper even after rubbing ?
Answer:
The reason is some material acquire charge when we rub them and some may not acquire charge so they do not attract pieces of paper.

Activity – 2

Question 2.
Understanding types of charges:
Inflate two balloons and hang them in such a way that they do not touch each other. Rub both the balloons with woollen cloth and release them.

a) What do you observe?
Answer:
They repel each other. Take a refill and rub it with a polythene sheet. Keep it gently in a plastic tumbler. Take another refill and also rub it with the same polythene sheet.
Bring the second refill near the first one in the tumbler. Take care that you do not touch either of the rubbed portions on the refill with your hand.

b) Is there any effect on the first refill in the tumbler? Do they attract each other or repel each other?
Answer:
Yes, there is effect on the refill in the tumbler. They repel each other.

c) Now take a rubbed balloon near the rubbed refill in the tumbler and check the action. Do they attract each other or repel each other.
Answer:
They attract each other.
In the first two parts of the above activity, two objects that were made of the same material have brought near to each other after being rubbed with some appropriate material.

In the third part, objects made of different materials were brought near to each other after being rubbed with some material.
Let us summarise our observations carefully.

1. A balloon rubbed with woollen cloth repelled another balloon of the same type.
2. A refill rubbed with polythene repelled another refill rubbed with similar material.
3. A ballon rubbed with woollen cloth attracted by a refill rubbed with polythene sheet.

d) What can we conclude from these observations?
Answer:
Some charged objects are attracted and some charged objects are repelled with each other.

e) Does the repulsion between charged balloons indicate that they possess similar charge?
Answer:
Yes, they possess similar charge.

f) Does the attraction between charged balloon and a charged refill indicate that they possess different charges?
Answer:
Yes, they possess different charges.

g) Does this activity remind you some of experiments that you have done in “Playing with Magnets” Chapter of class VI?
Answer:
Yes, we know that magnets attract objects made up of magnetic materials like iron, nickel, cobalt, etc.
We also know that unlike poles magnet attract each other and like poles repel each other.

h) Can we say that something similar is happening in above activities?
Answer:
Yes.

i) Does it indicate that the charge on the balloon is of a different kind from the charge on the refill?
Answer:
Yes, it indicate they are different charges.

j) Can we say that there exist two kinds of charges?
Answer:
Yes, there exists two kinds of charges.

k) Can we also say that the charges of same kind repel each other, while charges of different kinds attract each other?
Answer:
Yes, it is convention to call the charge acquired by a glass rod when it is rubbed with silk cloth positive and charge acquired by a silk cloth is negative.
It is observed that when a charged glass rod is brought near a charged plastic straw which is rubbed with polythene sheet, there is attraction between the two.

l) What do you think about the kind of charge on the plastic straw?
Answer:
The plastic straw would carry negative charge.

m) Is your guess correct or wrong? Discuss with your teacher.
Answer:
My guess is correct because opposite charges attract each other which I confirmed by discussing with my teacher.

Activity – 3

Question 3.
Conduct an experiment to find out the presence of charge on a body.
Make a small ball of thermocol. Collect thin silver foil used to decorate sweets.
Wrap this thin silver foil to cover the thermocol ball and suspend it from a stand with the help of thread as shown in figure.

Bring a glass rod which is rubbed with a silk cloth near the suspended ball.
a) What happens ? Does it get attracted towards the glass rod or move away from it?
Answer:
It will attracts towards glass rod.
Now touch the silver foil on the thermocol ball with charged glass rod. Remove the glass rod from the ball and against rub it with silk cloth and bring it close to the suspended ball.

b) What do you observe?
Answer:
The suspended ball moves away from the glass rod.

c) What could be the reason for this change in movement of the ball?
Answer:
In the above activity when a charged body brought near an uncharged body it induces an opposite charge in it and hence it get attracted by the glass rod.
In the second case we have charged the thermocol by touching it with a charged glass rod. Hence when we brought the glass rod near the ball, as both of them have similar charge the ball gets repelled by the glass rod.
From the above activity we can conclude that attraction is not a sure test to know the presence of charge on a body.

Activity – 4

Question 4.
Describe with the help of a diagram an instrument which can be used to detect a charged body.
Take an empty jam bottle. Take a piece of cardboard slightly bigger in size than the mouth of the bottle.
Pierce a hole in it so that a metal paper clip could be inserted.

Open out paper clip as shown in the figure.
Cut two strips of aluminium foil about 4 cm x 1 cm each and hang them on the paper clip.
Insert the paper clip having the strips of aluminium foil in to the cardboard lid so that it is perpendicular to it as shown in the figure.
Change a refill and make it touch the end of the paper clip. Observe what happens.
a) Is there any effect on the strips of aluminium foil?
Answer:
Yes.

b) Do they repel each other or attract each other?
Answer:
They repel each other.

c) Now bring other charged bodies and make them touch the end of the paper. Do the foil strips behave in the same way in all cases?
Answer:
Yes, it behave in the same way in all cases.

d) Can this apparatus be used to detect the presence of charge on a body or not?
Answer:
Yes, it is used to detect the presence of charge on a body.

e) Can you explain why the strips repel each other?
Answer:
The strips of aluminium foil receive the same charge from the charged refill through the paper clip. The strips carrying similar charges repel each other and hence they move apart.
This device can be used to test whether an object is carrying charge or not. This device is known as electroscope. In the above activity you can observe that electric charge can be transferred from a charged object to another through a metal conductor.
Touch the end of the paper clip gently with hand and you will find a change in the foil strips they move closer and come back to their original state.

f) Why does it happen?
Answer:
The reason is that the foil strip lose charge to the earth through your body. We say that the foil strips are discharged.
The process of transferring of charge from a charged object to the earth is called earthing.

Activity – 5

Question 5.
Collecting information about the damages caused by earthquakes:
Ask your parents about the huge damages to life and property caused by these earthquakes. Collect a few pictures showing the damage caused by these earthquakes from newspapers and magazines of those days.
Prepare a short report on the suffering of the people during the earthquakes.
Answer:
Report: It caused damage to human life and property on a hugescale. Due to tsunami thousands of people died in the coastal areas of Andhra Pradesh and Tamilnadu. People lost their shelter.
a) What is an earthquake?
Answer:
An earthquake is a sudden shaking or trembling of earth lasting for a very short period of time. It is caused by a disturbance deep inside the earth’s crust.

b) What happens when it occurs?
Answer:
When it occurs it can cause damage to human life and property on a huge scale.

c) What can we do to minimize its (earthquake) effects?
Answer:
People living in seismic zones, where the earthquakes are more likely to occur, have to be specially prepared. The buildings in these zones should be designed so that they can with stand major tremors.
Steps to be taken in building construction:

1. In highly seismic areas, the use of mud or timber is better than heavy construction material.
2. Keep roofs as hieght as possible. In case the structure falls, the damage will not be heavy.
3. It is better if the cupboards and shelves are fixed to the walls so that they do not fall easily.
4. Be careful where you hang wall clocks, photoframes, water heaters, etc. so that in the event of earthquake, they do not fall on the people.
5. Since some buildings may catch fire due to an earthquake, it is necessary that all buildings, especially tall buildings have fire fighting equipment in working order.

Measures to be taken in a house when earthquake occurs.

1. Take shelter under a table and stay there till shaking stops.
2. Stay away from tall and heavy objects that may fall on you.
3. If you are on bed, do not get up. Protect your head with a pillow.

Measures to be taken outdoors when earthquake occurs.

1. Find a clear spot, away from buildings, trees and overhead power lines. Drop to the ground.
2. If you are in a car or a bus, do not come out. Ask the driver to drive slowly to a clear spot. Do not come out till the tremors stop.

Activity – 6

Question 6.
Locating the tsunami affected areas in the map:
Take an outline map of the world. Locate the eastern coast and Andaman and Nicobar Islands in India. Mark other countries around the Indian Ocean which could have suffered damage.
Collect accounts of the devastation caused by the tsunami in India from your parents, or other elders in the family or in the neighbourhood.
Answer:

Devastation due to tsunami:

1. Loss of lives, families and friends.
2. Loss of properties.
3. Loss of jobs and living.
4. Emotional challenge.
5. Loss of livestock.
6. Dramatic or drastic changes to a whole community’s routine living.
7. Negative impact on the affected regions, economy.
8. Negative impact to the affected region’s tourism.

To the environment:

1. Alternation to seaside terrain.
2. Minor deforestation in the area effected by the tsunami.
3. Wild life casualities.
4. The sea will be temporarily littered with debris after the tsunami.

AP State Syllabus AP Board 8th Class Physical Science Solutions Chapter 12 Stars and the Solar System Textbook Questions and Answers.

AP State Syllabus 8th Class Physical Science Solutions 12th Lesson Stars and the Solar System

8th Class Physical Science 12th Lesson Stars and the Solar System Textbook Questions and Answers

Improve Your Learning

Question 1.
What is your local noon time?
Answer:
The time when the shortest shadow of a vertical object occurs in a particular place is called local noon time at that place.

Question 2.
Where do you find moon at night?
a) 2 days before Poumami
b) 2 days after Amavasya
Answer:
a) Couple of days (2 days) before full moon day (Pournami), a crescent is seen in the west just after sunset.
b) Couple of days (2 days) after the new moon day (Amavasya), a crescent is seen in the west just after sunset.

Question 3.
Why doesn’t eclipse occur on every full moon day or on every new moon day?
Answer:
Lunar eclipse can happen during a full moon and only when the moon and earth and sun are directly in line and the moon passes through the earth shadow. Most of the time the moon is slightly out of line and that is why we don’t have a Lunar eclipse every full moon.

Question 4.
Where do you find the pole star?
Answer:
The pole star lies on the line joining the two outer stars of the constellation great bear. Pole star directly above the north pole of earth.

Question 5.
What Is the difference that you find between pole star and other stars?
Answer:
If we observe the position of various stars constantly. We will notice that they are not in a fixed position because as the earth rotates about a fixed axis, the position of stars with respect to earth changes. But the position of pole star does not change with respect to earth.

Question 6.
Why does polestar seem to be stationary?
Answer:
The polestar is situated in the direction of the earth’s axis and that is why it does not appear to move even though all stars appear that they are moving because of ie rotation of earth. So pole star seems to be stationary.

Question 7.
Name some constellations.
Answer:
Names of some constellations:

1. Great bear (Saptarishi)
2. Cassiopeia (Sharmistha)
3. Orion
4. Leo (Simha)
5. Corona
6. Borealis

Question 8.
How many planets are there in our solar system? What are they?
Answer:
There are 8 planets in our solar system. They are:

1. Mercury
2. Venus
3. Earth
4. Mars
5. Jupiter
6. Saturn
7. Uranus and
8. Neptune.

Question 9.
Look at the below table and name the smallest and the biggest planets in our solar system.

Answer:
From the table the biggest planet is Jupiter and the smallest planet is Mercury.

Question 10.
Among all 8 planets what is the special thing about earth?
Answer:
The special thing about earth is it is the only planet in the solar system on which life is exist.

Question 11.
How do day and night occur?
Answer:
The day and night occur due to rotatory motion of earth.

Question 12.
Do the stars appear moving? How can you say?
Answer:
Yes, stars are appear moving. Our galaxy like all other spiral galaxies is rotating. The stars move on orbits around the centre of the galaxy. It was the motions of stars in external galaxies that lead to the idea of dark matter in the universe. Stars also have some random motions. They do not orbit galaxy in exact circles. As observers we see this motion of the stars as what is called proper motion, the projection of their velocity on to the plane of the sky is radial motion.
Normal Answer : Alternate answer is No. All the stars appears that they are moving because of rotation of earth.

Question 13.
Is it possible to see the polestar for the people who live in the southern hemisphere of the earth? Why?
Answer:
A pole star is a visible, preferably a prominent one, that is approximately aligned with the earth’s axis of rotation. The term polestar refers to polaris which is the current northern pole star also known as the north star. So the people in southern hemisphere unable to see this pole star.

Question 14.
What is the use of artificial satellites in our daily life?
Answer:
Artificial satellites have many uses in daily life.

1. They are used for forecasting weather.
2. They are used for transmitting television and. radio signals.
3. They are also used for telecommunication.
4. They are used in aviation and military (these satellites are called remote sensing which will collect information from a distance).

Question 15.
Why is Venus the brightest planet?
Answer:
Venus is very bright that’s partly because sunlight easily reflected by acidic clouds that blanket the planet atmosphere and also it is closest planet to earth.

Question 16.
Are you curious about going to the moon? Why?
Answer:
Yes, I am curious about going to moon. Because I want to find answers raised in my mind.

1. Is it true there is no life on moon?
2. If it does not have atmosphere, how it look like?
3. How earth look like from moon?
4. Whether there are any mountains on moon or not?
5. There may be any creators on moon or not?
6. Whether there is any form of water exists on moon?
7. Whether we able to walk on moon as freely as on earth surface?

Question 17.
While observing the shadow of a stick from morning to evening, some questions arose in Ramya’s mind. What may be those questions?
Answer:

1. Why sun is changing its position from morning to evening?
2. How does the length of the shadow change with time?
3. Why we are getting longest shadows in the morning and evening?
4. Why the shadow in the noon is shortest?
5. Do all the days at noon have same size of shadow?

Question 18.
What are the questions that engage your mind when you look at night sky?
Answer:

1. Is stars collide with each other?
2. Where does the stars go in the morning?
3. Whether stars daily travel in the same path?
4. Why night sky is black and early morning sky is blue?
5. Whether we can count stars in the sky?
6. Why stars grouped to form constellations?

Question 19.
Even though we do not have clock, we can know the time by observing some shadows in daytime. Think and discuss with your friends how we can know the time at night?
Answer:
We can know the time by position of moon and stars or with reference to pole star. Estimation of time by using position of moon:

1. If the moon is full do the experiment stop if it is new moon.
2. Imagine the moon is divided into 12 vertical strips. First hour at right edge and last hour at left edge. It can vary by season or location.
3. Read the moon from left to right following an imaginary horizontal half line.
   Look for where the line intersects the boarder between light and dark. Make a note of which strip that intersection is in.

For example:
The instruction is at 8 pm and transition from right to left is from light to dark. This tells us the moon will set in the west at 8 pm.
This moon will set at about 7-8 hours after sunset. If sunset is at 8 pm. You can expect moon time is at 3-4 am.

Question 20.
How can you find north – south direction at your place?
Answer:
This experiment should be performed on a day when the sky is clear, preferably between nine in the morning and four in the evening.

Pick a spot in open ground away from buildings and trees. The spot should be as flat as possible.
Take a stick which is a little over a meter long and fix it vertically in the ground. Ensure that exactly one meter of stick remains above the surface of ground. Build a fence around your stick as shown in figure.
Make your first observation at nine in the morning, Make a mark with a nail or peg at the point where the tip of the shadow falls on ground. Measure the length of the shadow.
Then, make similar observations for every half an hour throughout the day till four in the evening.
Find the direction of shortest shadow cast by vertical object on the ground. That gives the north-south direction.

Question 21.
In which direction (towards north or south) is the sun moving day by day when you read this lesson?
Answer:
From December 21 to till June 21 the sun appears to shift northward. From June 21 to December 21 the sun appears to shift southward.
(Basing on this information we have to give the answer suppose you have read the lesson in the month of February the sun is moving towards north direction).

Question 22.
What are the planets you have seen in the sky? When do you observe those planets?
Answer:
The two planets observe in the sky are

1. Venus: Sometimes Venus appears in the eastern sky before sunrise. Sometimes it appears in the western sky just after sunset. Therefore it is often called a morning or an evening star.
2. Mars: It appears slightly reddish and therefore, it is also called red planet. It appears in the east.

Question 23.
What is the duration of a day and night today? Collect the information about duration of day and night for the past 7 days from the newspapers, analyze it and say whether summer or winter is going to come.
Answer:
Students have to collect the information from newspaper and other resources.
(Hint: If sun is shifting towards south the upcoming season is winter if it is shifting towards north the upcoming season is summer).

Question 24.
What are the other districts on the same latitude as your district ?
Answer:
I am residing at Krishna district. The latitudes of Krishna district are 16. The other districts which have same latitude are West Godavari, Mahaboobnagar.
(You should write the latitude of your district and you have to find out the districts which lie in that latitude from table -1 on page 163 of textbook.)

Question 25.
Collect the information about cosmic dust (wastage) from newspapers, internet and make a poster on your school panel board about the consequences of cosmic dust.
Answer:
Cosmic dust: Cosmic dust is a type of dust composed of particles in space which are a few molecules to 0.1 mm in size.
Consequence of cosmic dust:
The orbit of space junk could deteriate resulting in the junk falling to earth. If it survives and reaches the earth’s surface it would cause the same damage as equally sized meteorite, including damaging or destroying structures in the area killing people, etc.
The earth receives hundreds of tonnes of space dust, rocks, etc every week. If you were to get whole load of it in one place and try and breathe it in it probably would be harmful. However natural concentrations are so low that it possess no risk.

Question 26.
Make a sundial. Explain how you made it.
Answer:
Making of sundial:
Cut a right angled triangle ABC from a sheet of cardboard. Angle C of the triangle should equal to the latitude of your city or town and angle A should be 90° as shown in figure.

Fix cardboard triangle vertically in the middle of a rectangular wooden board. Glue strips of paper along both edges of BC and the wooden board to make the triangle stand erect.
Place your board with the triangle on level ground in an open space which gets sunlight throughout the day. Base BC of the triangle should be placed in the north- south direction, with B pointing to the north.
At nine in the morning, draw a line along the shadow of side AC on the wooden board. Write the time along side of the line. Draw lines of the shadow of side AC at one hour intervals through the day till sunset and mark the time for each line. The sundial is now ready.

Question 27.
Draw the different phases of moon. Arrange them in an order from poumami to amavasya.
Answer:

Question 28.
Draw the location of polestar showing the direction from Great Bear.
Answer:

Question 29.
Draw the diagram of the solar system.
Answer:

Question 30.
How do you appreciate the construction of knowledge about the universe by our ancestors?
Answer:
They study of our universe changed from time to time from earth is flat to higgs bosan particles. All these secrets about our universe are revealed due to constant afforts of our ancestors. That is due to construction of knowledge about the universe by our ancestors. So the afforts of our ancestors should be thoroughly appreciated.

Question 31.
We launched so many artificial satellites around our earth for different purposes. What do you think about the impact of artificial satellites and their radiation on bio-diversity?
Answer:
Effect of radiation released from artificial satellites on biodiversity:
I. Animals and humans:

1. Killing certain enzymes in the body can simply make sick.
2. If radiation damages DNA, the body may not repair it. It increases the chances of both animals and humans developing cancer.

II. Marine animals: High level of radiation cause a reduction and reproduction capabilities of marine animals.
III. Plants: Weaking of seeds and frequent mutations. Excess of radiation killing plants.

Question 32.
Among eight planets of our solar system, earth is the only planet supporting life. Explain how we should protect our earth and its environment.
Answer:
Steps to be taken to protect earth and environment:

1. Reduce pollution by reducing air, water and land pollution.
2. Recycle resources by sending the degradable like paper and non degradable like plastic and glass objects to recycling factory.
3. Save resources by using them carefully. E.g.: Water, trees, wood, paper.
4. Stop burning fossil fuels (Coal, oil and natural gas) for that do not waste electricity.
5. Plant lot of trees.

8th Class Physical Science 12th Lesson Stars and the Solar System InText Questions and Answers

8th Class Physical Science Textbook Page No. 160

Question 1.
What are the celestial objects that we can see in the sky?
Answer:
Stars, Planets, Moon (Satellite), Comets, Meteors and Meteorites are the celestial objects that we can see in the sky.

Question 2.
Are the stars moving?
Answer:
Yes, the stars are moving.

Question 3.
Do you see the same stars at night and early in the morning?
Answer:
No, we do not see the same stars at night and early in the morning.

Question 4.
Do you see the same stars during summer and winter nights?
Answer:
Yes, it is due to the change of axis of rotation of the earth.

Question 5.
What is the shape of the moon? Why does it change? Why doesn’t the sun change its shape daily like the moon?
Answer:
The actual shape of the moon is approximately spherical.
But it changes everyday.
The sun does not change its shape like the moon due to its size and the distance it is away from the earth. Moreover the shadow of the earth falls on one side of the moon partially or fully. This makes the changes in its shape. Also the moon does not have its own light to make the shadow of the earth to fall on the huge sun.

Question 6.
Where exactly is the sun situated in the sky at noon?
Answer:
Above our head (vertically above) (Really the sun does not revolve around the earth but due to the rotation and revolution of the earth we feel / imagine that the sun moves around the earth.)

Question 7.
Why does the shadow of a tree change from morning to evening?
Answer:
Due to the rotation of the earth we find the sun at different positions in the sky which brings the tree the different shadows from morning to evening.

8th Class Physical Science Textbook Page No. 168

Question 8.
Will we be able to hear any sound if we were on the moon? Why?
Answer:
Sound required a medium for its propagation. There is no atmosphere (medium) on moon. We know sound cannot travel in vacuum. So we unable to hear any sound if we were on the moon.

Question 9.
Can any life exists on the moon? Why?
Answer:
Moon does not have air (oxygen) and water which are essential for existence of life. So there is no life exists on moon.

8th Class Physical Science Textbook Page No. 169

Question 10.
Why does lunar eclipse occur only on a full moon day?
Answer:
Lunar eclipse occur only on a full moon day because lunar eclipse happen when the earth’s shadow falls on the moon, hiding it from the sun’s light. For this to happen, the moon must be on the opposite side of the earth from the sun. So the full half of the moon that is lit by the sun is visible from earth that is full moon day.

Think and Discuss

8th Class Physical Science Textbook Page No. 161

Question 1.
Look at the nails or pegs you have fixed on the ground to keep track of the shadow of the stick throughout the day. From their positions, can you tell how the position of the sun changes in the sky from sunrise to sunset?
Answer:
The position of sun changes from slanting to vertical and then vertical to slanting.

8th Class Physical Science Textbook Page No. 163

Question 2.
Why does the sun appears to travel towards north or south? Try to find the answer by reading your social studies chapter “Earth movements anti seasons” along with this lesson.
Answer:
The earth’s tilt is constant 23.5 degree perpendicular. The earth position relative to sun changes, not the tilt itself during orbit. The sun is moving towards north throughout summer because the north pole is tilted 23.5 degree towards sun and we are in northern hemisphere. During the winter the south pole is tilted 23.5 degree so the sun appear to travel towards south.

8th Class Physical Science Textbook Page No. 168

Question 3.
Scientists are planning to build settlements on moon and are trying to make arrangements to live there. You know that there is no air on moon. How will it be possible to live on the moon then?
Answer:
Oxygen is essential for humans. Unless we built special structures and buildings on the moon and put oxygen into them, we would not able to live on the moon without wearing oxygen tanks all the time.

8th Class Physical Science Textbook Page No. 178

Question 4.
The diameter of the sun is 13,92,000 Km. The diameter of the earth is 12,756 Km. The diameter of the moon is 3,474 Km. The distance from the sun to earth is 15,00,00,000 Km. The distance from the earth to moon is 3,84,399 Km.
Take the scale as 1 lakh km = 1 cm, and imagine how the arrangement of sun, earth and moon is in our universe. Can you make this arrangement on your school ground?
Answer:
Yes, we can do it in our play ground. Placing sun at the middle. Rotating earth around sun and rotating moon around earth by measuring diameters in cm.

8th Class Physical Science 12th Lesson Stars and the Solar System Activities

Activity – 1

Question 1.
Observing the changes in the length of shadow.
This experiment should be performed on a day when the sky is clear, preferably between nine in the morning and four in the evening.

Pick a spot in the open ground away from trees and buildings.
The spot should be as flat as possible. Take a stick which is a little over a meter long and fix it vertically in the ground. Ensure that exactly one meter of stick remains above the surface of ground.
Make your first observation at nine in the morning. Make a mark with a nail or peg at the point where the tip of the shadow falls on ground. Measure the length of the shadow.
Then, make similar observations for every half an hour throughout the day till four in the evening.
Use a clock to fix the time for making your observations. Enter the measurements of the length of the shadow and the time of measurement in a table making two columns, one for time and another for length of shadow.

Time	Length of the shadow
9.00 am	1.75 m
9.30 am	1.7 m
10.00 am	1.6 m
10.30 am	1.5 m
11.00 am	1.1 m
11.30 am	0.8 m
12.00 noon	0.7 m
12.30 pm	0.81 m
1 pm	1.12 m
1.30 pm	1.3 m
2.00 pm	1.5 m
2.30 pm	1.75 m
3.00 pm	1.84 m
3.30 pm	2.2 m
4.00 pm	2.5 m

(These values are changes from place to place and with seasons)
a) Look at your table and figure out the time of the day of shortest shadow.
Answer:
I observed at 12 noon.

b) When did you observe the longest shadow in your activity?
Answer:
At 4 pm.

c) How does the length of the shadow change with time? Illustrate your answer with the help of some diagrams. Draw the diagrams of the stick and its shadow for 5 different times, that is, at 9am, 1 lam, 12noon, 2pm and 4pm.
Answer:
The size of the shadow decreases and reach a minimum and then increases (It has minimum value at 12 noon)
(Students have to draw the diagrams of the stick and its shadow at 9 am, 11 am, 12 noon, 2 pm and 4 pm by doing this activity)

d) If you continue your activity from sunrise to sunset, at what times do you think the shadow would be the longest?
Answer:
At sunrise and at sunset.

e) Where is the sun situated in the sky at noon? Where does the shadow of stick is fall at that time? Think about how your own shadow will be at that time.
Answer:
Almost in line with the stick. It will falls in north-south direction. My own shadow is also in north-south direction.

f) Do you think that your shadow length will be the same on all the days at noon?
Answer:
Yes, the shadow will be same on all the days (with in two weeks).

g) In which direction does the shortest shadow of the stick fall in your activity?
Answer:
The shortest shadow falls in the north-south direction.
Continue your observations.

h) Observe on the next day whether the shadow of the stick falls at the same spots at the same times throughout the day.
Answer:
Yes, it falls on the same spot.

i) Can you use your stick as a clock (sundial) to tell the time? If your answer is ‘yes’, explain how this is possible.
Answer:
Yes, due to movement of sun from east to west.

j) Two weeks later, once again check to see whether the stick’s shadow falls at the same spots at the same times during the day.
Answer:
It fall on the same spot. But length of shadow change.

k) If the shadow does not fall on the same spot, what could be the possible reason?
Answer:
The position of the sun in the sky changes during the day.

l) If you continue the experiment the position of shadow changes or not ?
Answer:
No, it does not change. The position of sun changes from day to day as well.
That is, the position of the sun at 10.00 am today will be different from its position two weeks later at the same time. If you choose a particular time every week and mark the position of the sun with a peg at that time, you can build a calendar for the full year.

m) During a period of two weeks you had made an observation that the length of the shadow at a particular time is changing day by day. Did it become longer or shorter?
Answer:
Yes, it is changing day by day. During summer it is shorter day by day and during winter it is larger day by day.

n) By observing the direction of shadows, can you guess the arrival of summer or winter?
Answer:
Yes.

Activity – 2

Question 2.
Understanding the north-south movement of the sun.
Fix a spot near your home from where you can observe the sunrise. You may have to go to the terrace of a RCC building or go to an open field for the purpose. Choose a tree or an electric pole or some other stationary object as a reference point.

Over the next 10 to 15 days, note the spot at which the sun rises daily, keeping in mind your reference point. Make a daily sketch of the rising sun as well as your reference point in your notebook during this period.
a) Does the spot of sunrise change? If it does, in which direction does it seem to move?
Answer:
It may moves towards south of the sky if it is Dakshinayanam or it may moves towards north of the sky if it is Uttarayanam.
(So answer based upon Uttarayanam or Dakshinayanam)

b) Was the sun appear travelling towards south or north during the time you made your observations?
Answer:
It is travelling towards north.

c) Do you think that is the reason for the change in the length of the shadow of the stick day by day in activity 1 ?
Answer:
Yes, that is the reason.

d) Assuming that you did not have any calendar and knowledge of months and seasons, can you use movement of the sun to predict the arrival of winter or summer?
Answer:
Yes, if it is moving towards north, the coming season is summer (in the above case it is summer) and if it is moving towards south, the coming season is winter.

Activity – 3

Question 3.
Make your own sundial.
Answer:
First of all, you will need to cut a right angled triangle ABC from a sheet of cardboard. Angle C of the triangle should equal to the latitude of your city or town and angle A should be 90° as shown in figure.

A list of latitudes of districts of Andhra Pradesh is given below in table.

Fix your cardboard triangle vertically in the middle of a rectangular wooden board. Glue strips of paper along both edges of BC and the wooden board to make the triangle stand erect.
Place your board with the triangle on level ground in an open space which gets sunlight throughout the day. Base BC of the triangle should be placed in the north- south direction, with B pointing to the north.
At nine in the morning, draw a line along the shadow of side AC on the wooden board. Write the time along side the line. Draw lines of the shadow of side AC at one hour intervals (use a clock to check the time) through the day till sunset and mark the time for each line. Your sun-dial is ready.

Activity – 4

Question 4.
Observing phases of the moon.
a) Have you ever observed the movement of moon in the sky?
Answer:
Yes.

b) Does the moon appear at same point at a particular time everyday?
Answer:
Yes.

c) s the shape of the moon same on everyday?
Answer:
No, it changes.

Now note the date of the day after new moon day (amavasya), when the moon first appears in the sky.
Also note the time at night when the moon sets (goes down in the western sky). In the same way everyday locate the moon in the sky at the time of sunset or immediately after sunset.
Record the date and time of the moon set and draw a picture of the moon as you see it on that day in your notebook as shown in figure.
Continue making observations for as many nights as possible.
Observe the moon a few days before full moon day (Pournami) to a few days after it. Locate the position of moon in the sky at the time of sunset before Pournami and note the time and position of moon in the sky at that time.
After Pournami, note the time at which the moon rises (comes in the eastern sky) and also note the date. Draw pictures of the shape of the moon each of these days.

d) Can you calculate the number of hours between one moon rise and the next moon rise or the number of hours between one moon setting and the next moon setting, with help of these observations?
Answer:
It is about 24 hours and 50 minutes.

e) How many hours lapse between one sunrise to the next, or one sunset to the next?
Answer:
It is about 24 hours.

f) Is the time period same for sun and moon to appear at selected position after completing a cycle in the sky every day?
Answer:
No, they are different.

g) Does the moon appear at the same point every day during the time of the sunset?
Answer:
No.

h) What is the shape of the moon? Is it same every day?
Answer:
It is changing day by day.

i) You might have observed that the shape of the moon changes night after night. What is the name given to these changes in appearance ?
Answer:
These changes in its appearance are called the phases of the moon.

j) Can you guess why the shape of the moon changes?
Answer:
The time period taken by sun to complete a cycle in the sky and come to the selected position is almost same everyday and it is about 24 hours i.e., 1 day. Whereas moon takes about 50 minutes more than a day to complete the cycle and which results in the phases of moon.

Activity – 5

Question 5.
A Moon-shaped lemon.
Answer:
Choose a day one week after the new moon day when the moon is visible in the sky during the day time.
Take a yellow lemon or a whitewashed clay ball and pivot it on a long needle or on a spoke of bicycle. Hold it up towards the moon as shown in figure.

Ensure that you are standing in the sun¬shine when you do this activity.
Observe the shape formed by the sunlight on the surface of the lemon. Is there some similarity between the shape formed and the shape of the moon?
It forms one of the phase of moon.

Activity – 6

Question 6.
Why does the shape of the moon change ?
(Do this activity around 4p.m.)
Wrap a ball tightly with a white hand-kerchief or with a piece of white cloth.
Assume this is the moon. Hold this ball in front of your eyes in bright sunshine as shown in figure and turn around yourself slowly. Observe how the shape of the illuminated part of the ball changes.

a) Does sunlight fall on half the ball at all times while you turn around?
Answer:
Yes.

b) Is the shape of the illuminated part on the ball viewed by you same in all positions during your rotation?
Answer:
No, they are different.

c) Why does this happen?
Answer:
To understand this look at figure.

c) Why does this happen?
Answer:
To understand this look at figure.

The large circle in the middle of figure is the earth and the smaller circles around it represent the moon in different positions. We can see the phases of the moon on different days in the figure. The sunrays falling on the moon illuminate half its surface in all the positions. However, we cannot see the entire illuminated surface in all the positions. In some cases we see the entire illuminated surface while in others we see only part of it. In one particular position, we cannot see the illuminated surface at all.
The shape of the moon we see is the shape of the illuminated portion visible to us.
In figure, the day of the new moon is called day 0 or day 28 (position 1). In this position, the illuminated surface is not visible from earth, so the moon cannot be seen from earth.
Four days later, when the moon is in position 2, a small part of its illuminated surface is not visible from earth. On day-7, the moon is in position 3, so more of its illuminated part is visible from earth.
After fourteen days (at position 5) the entire illuminated surface of the moon is visible from earth. This is the day of the full moon.
Subsequently, the moon appears smaller with each day as it passes through positions 6 (day-18), 7(day-21) and 8(day- 25). After 28 days, the moon is once again in position 1.
Try to duplicate position 1 with the ball. For this, you will have to hold the ball towards the sun (between your eyesight and the sun).

d) In this position, which half of the ball is illuminated?
Answer: Although half the surface of the moon is illuminated everyday, we cannot see the moon on new moon day since the illuminated surface is on the side opposite to the point of observation on the earth. On a full moon day, the situation is reversed. The illuminated half of the moon faces the point of observation, so we see a full moon.

e) Where is the position of sun and moon on new moon day and full moon day?
Answer:
The sun and moon must be on the same side of the earth on a new moon day and they are on opposite sides of the earth on a full moon day.

f) Can you now state as to in which direction the moon will rise on a full moon day?
Answer:
The moon will rise from west on full moon day.
While we observe moon in clear sky on a full moon day, we think about the spots those are visible on the moon. In olden days people are curious about the spots. This led to creation of a lot of stories.

e) Do you know any such story?
Answer:
One popular story to account for the dark spot on the moon is that Ganesha, once filled with food, fell from his mouse and broke his stomache. Chandra laughed at this, at which Ganesha injured him by breaking off and throughing one of his tusks and cursed him.

Activity – 7

Question 7.
Observing the movement of constellations (stars).
Take a 20cm x 20cm square sheet of paper and make a 1cm diameter hole in its center. Mark a cross ( X ) on one side of the sheet of paper as shown in figure.

Hold the sheet in front of your eyes with the ‘X’ mark at the bottom and look for the pole star through the hole. Once you have located the pole star, check in which direction the Great Bear and Cassiopeia lie.
Write ‘G’ for Great Bear and ‘C’ for Cassiopeia on the paper in the directions in which you see each of the constellations. Mark the timing at which you made your observation in both cases.
Choose a nearby tree or house as a reference point. Draw a picture of your reference point on the paper sheet taken, clearly indicating its location. Repeat your observations at one hour intervals. Ensure that you are standing on the same spot each time you look at the stars.
Write G, C in the direction of the position of the great bear and Cassiopeia during each observation and note the time of the observation next to the letters G and C.
Using the tree or house you have chosen as your reference point, check whether the position of the pole star has changed or not. If it has changed, note the changed position.
Repeat this activity as many times as possible, the minimum being four times. But ensure that the ‘X! mark on your sheet of paper remains at the bottom during all your observations.

a) Do the positions of the stars change with time?
Answer:
Yes, they will change.

b) Does the position of the pole star also change with time?
Answer:
No, it will not change with time.

c) Does the shape of the great bear and Cassiopeia change with time or does the position of the entire constellations in the sky change?
Answer:
The position of entire constellation changes.

d) What kind of path do these constellations trace in the sky?
Answer:
They traced in northern sky.

Activity – 8

Question 8.
Why does the pole star appears fixed at one point?
Take an umbrella and open it. Make about 10-15 stars out of white paper. Paste one star at the position of the central rod of the umbrella and others at different places on the cloth near the end of each spoke.

Now rotate the umbrella by holding its central rod in your hand. Observe the stars on the umbrella.
a) Is there any star which does not appear moving? Where is this star located? Is it located where the rod of the umbrella holds the cloth of the umbrella?
Answer:
Yes, it is located where the rod of the umbrella holds the cloth of the umbrella.

b) On similar lines, if there were a star located where the axis of rotation of the earth meets the sky, could this star is also be stationary?
Answer:
Yes, that is the reason pole star does not move even though all stars appear that they are moving because of rotation of earth.

AP State Syllabus AP Board 8th Class Physical Science Solutions Chapter 10 Reflection of Light at Plane Surfaces Textbook Questions and Answers.

AP State Syllabus 8th Class Physical Science Solutions 10th Lesson Reflection of Light at Plane Surfaces

8th Class Physical Science 10th Lesson Reflection of Light at Plane Surfaces Textbook Questions and Answers

Improve Your Learning

Question 1.
State the laws of reflection of light (OR)
Name the laws of reflection of light
Answer:
Laws of reflection:

1. When light gets reflected from a surface, the angle of reflection is equal to the angle of incidence, i.e., ∠i = ∠r.
   
2. The incident ray, the normal at the point of incidence and the reflected ray lie in the same plane, i.e., AO, ON, OB are in same plane.

Question 2.
How do you verify the 1st law of reflection of light with an experiment?
(OR)
Raghu found that for a plane mirror angle of incidence is equal to the angle of reflection. Write the experiment to prove this fact. (OR)
Prove: ∠i = ∠r (LAB ACTIVITY – 1)
Answer:
Aim: Verification of first law of reflection.
Required materials: Mirror strip, drawing board, white paper, pins, clamps, scale and pencil.
Procedure:

1. Take a drawing board and fix a white paper on it with the help of clamps.
2. Draw a straight line AB at the centre of the paper and also a normal (ON) to AB at the point ‘O’.
3. Draw a straight line PQ making certain angle (angle i) with ON.
4. Fix two pins at P and Q on the paper vertically.
   
5. Observe the images of pins – P’ of the pin P and Q’ of the pin Q, in the mirror kept along the line segment AB.
6. Fix two more pins R and S such that they are in the same line as that of P’ and Q’.
7. Join R, S and 0 as shown in figure.
8. Measure the angle between RS and ON (angle of reflection).
9. We will find that ∠i = ∠r. (angle of incidence = angle of reflection)
10. Repeat the experiment with different angles of incidence and measure the corresponding angles of reflection.
11. We can find angle of incidence = angle of reflection in all these cases.
    Thus first law of reflection is proved.

Question 3.
How do you verify the 2nd law of reflection of light with an experiment?
(OR)
John found that incident ray, reflected ray and normal drawn to surface lie on the
same plane. What are the apparatus required for this experiment? How are you able to prove this fact experimentally?
Answer:
2nd Law of reflection: The incident ray, the reflected ray and normal all lie in the same plane.

1. As shown in the figure, a light ray incident on a plane mirror and touches at a point ‘O’. Here AO is called incident ray.
2. When a ray of light falls on a mirror, the mirror sends it back in another direction OB. Here OB is called reflected ray.
3. Normal is a line which is perpendicular to the mirror at the point of incidence. So the line ON’ is the normal to the mirror surface at point ‘O’.
   
4. Here the incident ray (AO), the reflected ray (OB) and the normal (ON) all lie in the same plane of the paper.
   Hence 2nd law of reflection is proved.

Question 4.
Explain the image formation by pin hole camera with the help of the diagram.
(ACTIVITY – 1)
Answer:

1. Draw a ray diagram of the formation of an image in a pinhole camera.
2. Observe the flame of a candle with a pinhole camera making a big hole to it.
   
3. We can understand that the light rays coming from the top of the candle flame fall at different points on the screen.
4. Similarly, the rays coming from bottom of the candle points on the screen.
5. Thus, we get blurred image on the screen due to the big hole of the camera.

Question 5.
Find the plane of the reflection experimentally for the incident ray which passes through the heads of the pins pierced in front of the mirror.
(OR)
Sudheer wants to verify the laws of reflection. What apparatus he requires to prove them? State the laws of reflection and write the experimentation process he follows.
Answer:
Aim: Verification of laws of reflection.
Required material: Mirror strip, drawing board, white paper, pins, clamps, scale and pencil.
Procedure:

1. Take a drawing board and fix a white paper on it with the help of clamps.
2. Draw a straight line AB at the centre of the paper and also a normal (ON) to AB at the point ‘O’.
3. Draw a straight line PQ making certain angle (∠i) with ON.
4. Fix two pins at P and Q on the paper vertically.
   
5. Observe the image P’ of the pin P and Q’ of the pin Q, in the mirror kept along line segment AB.
6. Fix two more pins R and S such that they are in the same line as that of P’ and Q’.
7. Join R, S and O.
8. Measure the angle between RS and ON (∠r) .We will find ∠i = ∠r.
9. Repeat the experiment with different angles of incidence and measure the corresponding angles of reflection.
10. We find that each case angle of incidence is equal to angle of reflection. That is first law.
11. We can find that the incident ray is the ray which is passing through points P and Q touching the paper.
12. The reflected ray is the ray which is passing through the points R and S touching the same paper and ON is the normal to the mirror at O. All lie in same plane. That is second law which states incident ray, reflected ray and normal drawn to plane lie in the same plane.

Question 6.
Have you ever observed the image of the sky in rain water pools on earth? Explain the reflection of light in this context.
Answer:
Surface of the rain water pool acts as a plane mirror, because of its smooth surface. The light rays from the sky and clouds incident at this surface and reflect. Hence, the images of the sky and clouds appear in the rain water pools.

Question 7.
Discuss the merits and demerits of using mirrors in building elevation.
(OR)
What are the advantages and disadvantages of using mirrors in building elevation?
Answer:
Merits:

1. The mirrors used in elevating building are tough, reinforced and laminated glasses so they provide safety to the building.
2. They make the building attractive.
3. They absorb heat energy, so they cool inside the building.
4. If we use plane mirrors in building elevation it is easy to wash with water and no need of regular painting.

Demerits:

1. Elevation of buildings with mirrors is not suggestable.
2. These mirrors reflect sun rays at day time and reflects lighting from near by electrical bulbs at night time, which causes confusion and disturbance for the vehicles and people who are running on the nearby roads lead to accidents.
3. Birds like sparrows, crows will get confusion while flying on roads.
4. They are also not safe enough to the buildings, which causes easy access to thieves.
5. This glass elevation is not environmental friendly, because natural air does not enter into the building.
6. They are easy to break and cause cuts and wounds.

Question 8.
If a ray incidence normally on a plane mirror, what will be the angle of reflection.
Answer:
If a ray incidence normally on a plane mirror, the angle of reflection will be zero.

Question 9.
Why does the image in plane mirror suffers lateral inversion?
Answer:
The light rays which come from our right side get reflected from the plane mirror reach our eye. Our brain feels that the rays is coming from the inside of the mirror. That is why our right side looks like left side in the image. This is called right-left inversion or lateral inversion.

Question 10.
Draw a ray diagram to understand the formation of image for a pointed object by a plane mirror explain it.
Answer:
Observe the figure. ‘O’ is a point object.

Some rays from ‘O’ reach the mirror and get reflected. When we look into the mirror, the reflected rays seem to be coming from the point T. So, point I is the image of point object ‘O’.

Question 11.
In the adjacent figure, AO and OB are incident and reflected rays respectively angle ∠AOB = 90°. Find the values of angle of incidence and angle of reflection.

Answer:
We know that angle of incidence is equal to angle of reflection.
i = r …….. (1)
From the figure, ∠AOB indicates i + r = 90°
From (1)
⇒ i + i = 90°
2i = 90°
⇒ i = 90/2 = 45°
⇒ i = r = 45°
Angle of incidence i = 45°; Angle of reflection r = 45°.

Question 12.
Hinduja stands in front of a plane mirror at a distance of 5 m. from the mirror and observes her image in the mirror. If she moves 2 m. towards the plane mirror, then what will be the distance between Hinduja and his image?
Answer:
The distance between plane mirror and Hinduja = 5 m
The distance between plane mirror and Hinduja after moving 2 m towards mirror
= 5 – 2 = 3 m …….. (1)
The distance between plane mirror and Hinduja’s image after moving = 3 m …….. (2)
The distance between Hinduja and her image after moving = (1) + (2) = 3m + 3m = 6m.

Question 13.
Explain diagramatically the Image of letter ‘B’ in a plane mirror.
Answer:

Question 14.
Why can’t we see our image in a white sheet of paper though it reflects light?
Answer:
By microscopic observation, we can find up and downs over surface of a paper. Hence paper is not a smooth fine surface. Even though sheet of white paper reflects the light rays, they do not form an image of an object.

Question 15.
Observe the below figure. AB and BC are two plane mirrors arranged at 120°. A ray incidents at and angle 55° on AB. Find the value of ‘x’

Answer:
Let us say, angles a, b, c, d as shown in the figure. From the figure, a = 55° [∵ i = r]
a + b = 90° [. Normal to the plane]
55° + b = 90°
⇒ b = 90° – 55° = 35°
120° + b + c = 180° [∵ Total of angles in a triangle]
120° + 35° + c = 180°

⇒ c = 180° – 155° = 25° c + d = 90° [∵ Normal to the plane]
25° + d = 90°
⇒ d = 90° – 25° = 65°
d = x [∵ i = r]
∴ x = 65°

Question 16.
The size of the image in the mirror seem to be decreased when you move the object towards your eye from the mirror. Draw the diagram showing angles depicting the situation.
Answer:

Question 17.
Collect the information about “Situations using the plane mirrors and prepare the report.
Answer:
Plane mirrors have many uses.

1. Periscopes: They are used in periscopes to see bends and corners. It is used for observing enemy movements from trenches without any danger of being seen. Sailors on submarines use periscopes to see things above the water level.
2. Kaleidoscopes: Kaleidoscope is a toy that uses light and mirrors to reflect objects and create beautiful, fascinating repeating patterns.
3. Security: Mirrors are used while looking for explosives underneath a vehicle. Even these mirrors are used in shops to keep an eye on the customers. Mirrors are also used in blind turns of busy roads to see the vehicles coming from the other side.
4. Telescopes and Microscopes: Plane mirrors are used in many scientific applications like telescopes and microscopes.
5. Dressing mirrors: Plane mirrors are used in dressing tables to see ourselves, while dressing, shaving, etc.
6. Ophthalmic doctors: They use plane mirrors to increase the distance of the eye test chart while examine the eye of a patient.
7. Docorating mirrors: Plane mirrors are used to decorate the building for elivations. Some shops also used plane mirrors to get multiple images of the items in their shops.

MULTIPLE CHOICE QUESTIONS
1. Angle of incidence = Angle of reflection. This rule is explained by …………… principle        ( )
A) Fermat
B) Newton
C) Archemedes
D) Pascal
Answer: A

2. Which of the following letters doesn’t suffer lateral inversion?         ( )
A) C
B) O
C) B
D) N
Answer: B

3. A ray of light incidents on a plane mirror at an angle of 90° to its surface. What will be the angle of relfection?   ( )
A) 0°
B) 90°
C) 450°
D) 180°
Answer: A

4. If we move an object away from the plane mirror the size of images seems to be     ( )
A) increases
B) decreases
C) of the same size
D) image can’t be seen
Answer: B

5. Which of the following is incorrect with respect to the image in a plane mirror?     ( )
A) Image is erect
B) size of the image is same as the size of object
C) laterally inverted
D) image is real.
Answer: D

6. An object is placed 7cm distance from the plane mirror then distance of image is      ( )
A) 3.5 cm
B) 14 cm
C) 7 cm
D) 21 cm
Answer: C

8th Class Physical Science 10th Lesson Reflection of Light at Plane Surfaces InText Questions and Answers

8th Class Physical Science Textbook Page No. 134

Question 1.
How can we get the image of a big building in a small mirror?
Answer:
Light rays travel in all directions from one object. Light rays coming from a building incident on the small area of a plane mirror and reflect. These reflected rays reach our eye. We see the image of the building in the mirror.

Question 2.
Can we get the image formed by a plane mirror on a screen?
Answer:
Cannot.

Question 3.
Why is there lateral inversion, when we look into a mirror?
Answer:
Our brain feels that the rays is coming from the inside of the mirror.

Question 4.
Why is the angle of reflection equal to the angle of incidence when a light ray gets reflected from a surface?
Answer:
Light always choose the path of least time to travel.

8th Class Physical Science Textbook Page No. 138

Question 5.
Is the angle of reflection equal to the angle of incidence in all cases?
Answer:
Yes.

Question 6.
Do the two rays and the normal lie in the same plane? If yes, which is that plane?
Answer:
Yes, plane of paper.

Question 7.
In which plane will the incident ray, reflected ray and the normal lie?
Answer:
Plane touching the heads of pins and parallel to the plane of paper.

Question 8.
How will the incident ray be?
Answer:
Incident ray touching heads of the pins (P and Q) and make some angle with plane of the paper.

Question 9.
How will the reflected ray be?
Answer:
Reflected ray will make some angle with plane of the paper.

Question 10.
How will the normal be?
Answer:
The normal will also make same angle as incident and reflected rays.

Question 11.
How will the plane of reflection be?
Answer:
Plane of reflection make some angle (which is equal to plane of the paper and incident ray) with plane of the paper.

Question 12.
How does a mirror form the image of a pin or any object? Let us discuss.
Answer:
The rays coming from the pin get reflected from the mirror and seem to be coming from the image in the mirror.

8th Class Physical Science Textbook Page No. 139

Question 13.
What is the size of the image compared to the size of the object?
Answer:
Size of the image is equal to size of the object.

Question 14.
What do you say about the size of the image compared to the size of the object? Move the object towards your eye. What do you observe?
Answer:
Size of the image is same as size of the object. If we move the object towards our eye, size of the image of the object seems to be decreased.

Question 15.
Is the size of the image decreasing or increasing?
Answer:
Decreasing.

8th Class Physical Science Textbook Page No. 140

Question 16.
Why does an image suffer lateral (right-left) inversion? See the figure.

Answer:
Our brain feels that the rays are coming from the inside of the mirror and image is opposite to us. In this way image suffer lateral inversion.

Question 17.
What do you understand from the figure?
Answer:
The light rays which come from our right ear get reflected from the plane mirror and reach our eye. Our brain feels that the ray is coming from the inside of the mirror. That is why our right ear looks like left ear in the image.

Think, Discuss and Write

8th Class Physical Science Textbook Page No. 135

Question 1.
Does the explanation on pinhole match with your observation?
Answer:
Yes, it matches with my observation.

Question 2.
What happens if the hole Is much bigger, i.e., equal to the size of the flame?
Answer:
The image is extremely blurred.

Question 3.
If so, can we get the image of flame on the screen of pinhole camera? Why?
Answer:
No. Because the light rays coming from the top of the flame and bottom of the flame fall at different points on the screen. So it is blurred and is not formed on screen.

Question 4.
What happens if we observe the same flame with the same pinhole camera from a long distance?
Answer:
We may observe not only the flame, but the blurred image of entire candle.

Question 5.
What happens if we made two holes to pin hole camera?
Answer:
Two images will be formed.

8th Class Physical Science 10th Lesson Reflection of Light at Plane Surfaces Activities

Activity – 2

Question 1.
Which grain on the ground that a smart crow on tree A pick to reach B in short time (Shortest path)? Explain. (OR)
How do you support your answer to “When light gets reflected from a surface, it selects the path that takes the least time”? (OR)
Explain Fermat’s principle by using an activity.
Answer:

1. The crow can pick the grain from any point on the ground, but the condition is selecting the shortest path.
2. Let the speed of the crow is constants –
3. Observe some of the paths in figure.
4. To compare the lengths of these paths ACB, ADB, AEB and AFB, make the duplicates of them at point G as shown in figure.
5. In the figure CB = CG,
   ∴ The length of path ACB = AC + CB = AC + CG = ACG
6. Similarly length of the path ADB = length of the path ADG Similarlylength of the path AEB = length of the path AEG Similarly length of the path AFB = length of the path AFG
7. By observing the above paths, we will notice that AEG is the shortest path among all the paths, because it is the straight line distance between points A and G.
8. So the smart crow will pick the grain from point E.

Activity – 3

Question 2.
Look at the following figure.
Suppose if you have been given a plane mirror strip, what will you do to obtain figures as shown below figure (b) using mirror strip and the above figure (a)?

Answer:
The place of mirror that should be place on the figure vertically has been shown here under by a line.

In the above diagrams, line indicates the position of mirror to be kept to get the required shapes.

AP State Syllabus AP Board 8th Class Physical Science Solutions Chapter 9 Electrical Conductivity of Liquids Textbook Questions and Answers.

AP State Syllabus 8th Class Physical Science Solutions 9th Lesson Electrical Conductivity of Liquids

8th Class Physical Science 9th Lesson Electrical Conductivity of Liquids Textbook Questions and Answers

Improve Your Learning

Question 1.
Give examples for good solid conductors and liquid conductors.
Answer:
Examples for good conductors in solids:
Silver, copper, iron, graphite, etc.
Examples for good conductors in liquids:
Mercury, acid solutions (HCl, H₂SO₄), base solutions (NaOH, KOH), salt solutions (NaCl, KCl), etc.

Question 2.
Give examples for bad solid conductors and liquid conductors.
Answer:
Examples for poor conductors in solids:
Gold, platinum, etc.
Examples for bad conductors in liquids:
Distilled water, coconut oil, petrol, vegetable oil, kerosene, alcohol, etc.

Question 3.
What do you add to distilled water for making it to conduct electricity?
Answer:
Distilled water is poor conductor of electricity. In order to increase conductivity we should have to add either acid, base or salt. That will increase the conductivity of distilled water due to decomposition of these substances into constitute ions.

Question 4.
What is an electrolyte ?
Answer:
Electrolyte is a solution of substance through which current can pass.

Question 5.
Which energy is cause for glowing of bulb in electrolytic cell?
Answer:
Electrolytic cell is a device which converts chemical energy into electrical energy. So chemical energy stored in the cell is cause for glowing of bulb.

Question 6.
Write the uses of electroplating.
Answer:
Uses of electroplating:

1. Metals like iron are coated with deposits of nickel or chromium to prevent rusting.
2. Machinery parts are often chromium plated to protect them from corrosion and at the same time to give them good polish.
3. Electroplating is also used in repairing worn out parts of machinery.
4. Electroplating is also done for ornamentation and decoration purposes.
5. Processed food items are preserved in tin coated iron cans by electroplating method.
6. Zinc coated iron by electroplating method is used for bridges and in automobiles.

Question 7.
In case of a fire, before the fire men use the water, they shut off the main electrical supply for the area. Explain why they do this.
Answer:
Fire men use water to put out fire. Water containing dissolved salts is a good conductor of electricity. If fire men pour water on fire the electrical appliances near the fire may be wet if anybody touches those appliances they may have electric shock. In order to avoid people to get electric shock due to wet electrical appliances the fire men shut off electrical supply before they use water.

Question 8.
We get some items made from iron wire in which iron wire is coated with plastic. Is plastic coated by the process of electroplating? Why plastic cannot be coated on a metal by the process of electroplating?
Answer:
No. Plastic cannot be coated on a metal by using electroplating. The reason is plastic being a carbon polymer does not dissociate into ions. So it does not allow passage of current. So it does not act as an electrolyte. So electrolysis process is not possible with plastic which is main criteria for electroplating. So plastic cannot be coated on a metal by the process of electroplating.

Question 9.
Kavya observed that a discharged dry cell which kept in sunlight by her father for few hours got ability to glow LED. She got many doubts and questions to raise. Can you guess those questions or doubts? (OR)
Rohan observed that a discharged dry cell which kept in sunlight by his brother for few hours got ability to glow LED. He got many doubts and questions to raise. Guess the doubts or questions.
Answer:

1. Why does the bulb glow?
2. How does the dry cell charged?
3. Which energy is useful in charging the discharged dry cell?
4. Shall we use that energy to get rid from electrical power cut?

Question 10.
Explain the process of coating copper on iron key. Draw the circuit diagram.
(OR)
Conduct an experiment for coating on iron key with copper by electroplating method and prepare a note.
Lab Activity
Answer:
Aim: Coating an iron key with copper by electroplating method.
Required material: Copper plate of size 2 cm x 5 cm, crystals of copper sulphate, a key made by iron, glass beaker, water, sulphuric acid, battery cell and some connecting copper wires.
Procedure: Dissolve crystals of copper sulphate in pure water to prepare concentrated solution. Pour the solution in a beaker and add a few drops of dilute sulphuric acid to it.

Tie one end of connecting copper wire to iron object to be coated with copper. Connect other end to the negative terminal of battery. Suspend the tied iron object into the copper sulphate solution. Suspend the copper plate into copper sulphate from positive end of the battery through a switch as shown in the above figure. Key and plate are a little away from each other. Put the switch on for about 10 minutes. Switch the circuit off and take the iron key out.
We can observe a red coating on iron key. The reason is when electric current is pass through copper solution, in which copper sulphate is present in the form of copper and sulphate ions. The copper ion gets drawn to the electrode connected to the negative terminal of the battery and deposited on it.

Question 11.
How do you appreciate the efforts of Luigi Galvani and Alessandro Volta in discovering a cell and making a stored electric energy available to human beings?
Answer:
We should have to thoroughly appreciate the efforts of Luigi Galvani and Alessandro for their discoveries for the development of mankind. Galvani and Volta completely change the life of human beings. Before that people generated electricity in different ways and conduct various experiments. However they faced one major problem which prevented them from understanding electricity in depth. They did not have a stable and permanent source of electricity. Galvani experimental conclusion was a revolution in science saying that all living beings contained electricity and it was the main source of life.
Volta proved it is possible to generate electricity if two different metals are placed in some liquids. Volta made first cell using zinc and copper dipped in sulphuric acid. This cell called Volta cell. Later dry cell was prepared. Now various appliances works with dry cells. So the efforts of Galvani and Volta should be appreciated by every generation for their contribution to electricity.

Question 12.
Collect the information and make a list of good conductors and bad conductors. Mow do you use this information in your daily life works?
Answer:

Good conductors	Bad conductors
1) Metals	1) Wood
2) Acid solutions	2) Plastic
3) Base solutions	3) Diamond
4) Salt solutions	4) Distilled Water

Applications in daily life: This information is very useful to us. Generally metal or good conductors of electricity are used in electrical appliances, electrical wires, fuse wires, etc. Whereas plastic is a bad conductor is used for electric insulators like gloves, handles of electrical appliances etc. to avoid electric shocks.

Question 13.
Make a battery from four lemons and test it with a LED in the circuit.
(OR)
Write how do you make a battery from four lemons and test it with a LED in the circuit in your laboratory.
Answer:
Take four lemons cut them into two pieces. Take one piece from each lemon and insert two copper wires and connect them in series and connect a LED and complete the circuit. The circuit is shown below.

The bulb glows due to presence of current in the circuit. Here lemon juice acts as electrolyte and copper wires acts as electrolyte. So each lemon piece dipped with a copper wire acts as cell. These cells connected in series forms a battery.

Question 14.
Refer to the activity 3 in this chapter. Start with distilled water. The LED would not glow. Add two drops of some acid to distilled water and check the glow of LED. Add two more drops and check the intensity of the glow. Repeat the activity 5 to 6 times by adding 2 drops of the same acid each time. Do you see any difference in the intensity of glow with increasing acid content of water? What can be inferred from the above observations? Repeat the entire activity by taking a solution of baking soda and adding drops of it to distilled water instead of acid. Write differences and similarities.
Answer:
When we add two drops of acid (namely hydrochloric acid) to distilled water the LED will glow. If we further add the acid another two drops the intensity of glow increases. By repeating same activity 5 or 6 times we observe every time the glow of LED increases. The reason is acid dissociate into ions in aqueous solution. Which allows the passage of current. As the quantity of acid increases there will be more ions available for passage of electricity. So the intensity of glow increases.
We will observe the same result by adding baking soda but the intensity of glow is some what less when compared with addition of acid. The reason is baking soda is a weak base. So the dissociation is less when compared with acid. So less ions are available for passage of electricity. So the intensity of glow of LED is less when compared with acid.

Question 15.
In many of the activities in this chapter, we have used a tester made up of LED. Can we avoid LED and use something else as a tester Magnetic compass needle could be an alternative tester. We know that when we take a current carrying wire near magnetic compass needle, it shows deflection. Use this property to make a tester of magnetic compass needle. You may refer to the following figure.
Answer:
A magnetic compass wound with a copper wire is connected to one end of dry cell. The other end is connected to one of the two metal pins separated by a small gap in a rubber cap. The second pen is connected to the other end of dry cell to completed the circuit.

The magnetic needle deflects because whenever current pass through a wire it acts as a magnet is called magnetic effect of current.

8th Class Physical Science 9th Lesson Electrical Conductivity of Liquids InText Questions and Answers

Think and Discuss

8th Class Physical Science Textbook Page No. 123

Question 1.
Why some material allows electric current to pass through them and why some do not?
Answer:
Flow of charged particles constitutes current. So for the passage of current the material should have charged particles. All the materials do not have charged particles, e.g. Plastic, wood, diamond, etc. So only those material which have charged particles allow passage of current.

8th Class Physical Science Textbook Page No. 127

Question 2.
If a battery is packed in a box and if only two wires from two terminals are given out, how can we decide the positive and negative terminal of the battery?
Answer:
Insert the wires into a potato. A greenish spot is seen on potato at one of the wires. That wire behave like positive terminal and the other is negative terminal.

8th Class Physical Science Textbook Page No. 129

Question 3.
What is electrolysis?
Answer:
The dissociation of a solution of compound into constitute ions or elements by passing current is called electrolysis.
e.g. Electrolysis of water, which produce oxygen and hydrogen gases.

8th Class Physical Science 9th Lesson Electrical Conductivity of Liquids Activities

Activity – 1

Question 1.
Testing the material to know which allows electric current to pass through it.
Answer:
Take a torch bulb or LED (Light Emitting Diode), a dry cell, wooden sheet, two drawing pins, a key (safety pin) and pieces of connecting wires. Set up the electric circuit as shown in the figure.

Place the key on drawing pin. The bulb begins to glow as soon as the key touches the drawing pin. Now replace the key by a nail.
Does the bulb glow ?
Yes, the bulb glows.
Repeat the activity using different types of materials instead of the nail, say a strip of paper, a piece of chalk, a drinking straw, a piece of plastic, a paper clip, a rubber eraser, etc.
Note in each case whether the bulb glows or not and enter your observations in table.

Object	Material	Bulb glows Yes/No	Good conductor/ bad or poor conductor
Nail	Iron	Yes	Good conductor
Eraser	Rubber	No	Bad or poor conductor
Paper	Cellulose	No	Bad or poor conductor
Chalk	Calcium carbonate	No	Bad or poor conductor
Straw	Plastic	No	Bad or poor conductor
Plastic	Plastic	No	Bad or poor conductor
Matchstick	Wood	No	Bad or poor conductor

From the above activity, we conclude that some material allow electric current to pass through them. What we call them?
They are called good conductors of electricity.
The material that do not allow current to pass through them, what is the name given to those material?
They are named as bad or poor conductors of electricity.

Activity – 2

Question 2.
Testing the electric conductivity of liquids.
(OR)
Conduct an experiment for testing the electric conductivity of liquids.
Answer:
Take a LED, dry cell, metal pins, rubber cap of injection bottle and wires for making connections. Set up an electric
circuit shown in the figure.

See that the two metal pins, pass through the cap and should have a very small gap (around 2 mm) between them so that the pins are fairly closer but not touching each other. The LED should not glow when pins are separated by small distance.
Now, join the free ends of pins together by pressing them for a moment and make sure that the LED glows. Release the pins they get separated and LED should not glow. This acts as a tester.
Fill the rubber cap with different liquids like distilled water that we drink, coconut oil, kerosene, lime juice, mustard oil, sugar solution, etc one after another and in each case check whether the LED glows or not. Note down your observations in table.

Liquid	LED glows	Good conductor/ poor or bad conductor
Distilled water	No	Bad conductor
Drinking water	Yes	Good conductor
Coconut oil	No	Bad conductor
Lemon juice	Yes	Good conductor
Vinegar	Yes	Good conductor
Kerosene	No	Bad conductor
Vegetable oil	No	Bad conductor
Sugar solution	No	Bad conductor
Common salt solution	Yes	Good conductor
Milk	No	Bad conductor

a) Why doesn’t the LED glow in all the cases? Or why doesn’t the LED remain off in all the cases?
Answer:
The LED doesn’t glow all the cases because when the liquid the two pins of tester allows electric current to pass through, the circuit is completed (closed) and the LED glows. On the other hand when the liquid does not allow the current to pass through, the circuit is incomplete (open) and the LED does not glow.

b) In the above activity, you may have observed that in all those cases where the LED glows, its brightness (intensity) is not the same. Sometimes it may be brighter and sometimes it may be relatively dimmer. Why is that so?
Answer:
The intensity of the glow of the LED depends on the flow of electric current through the circuit. Although a liquid may be a conductor, it may not allow current through it as easily as a metal does.
As a result although the circuit is completed and the LED glows, due to weak current in case of some of the liquids, the intensity of glow would be lower compared to other liquids.

Activity – 3

Question 3.
Transforming a poor electric conductor into a good conductor.
(OR)
Conduct an experiment for testing the electric conductivity of electrolyte.
Answer:
Take some amount of distilled water in three different containers. Dissolve small quantity of common salt in the water of first container. Dissolve the copper sulphate, lemon juice in second and third container respectively.
Use the tester that we used in activity 2, and repeat the activity 2. Note the observations in table.

Material ‘	Does the LED glow? Yes/No	Good conductor/bad conductor
Distilled water	No	Bad conductor
Distilled water + salt	Yes	Good conductor
Distilled water + CuSO4	Yes	Good conductor
Distilled water + lemon juice	Yes	Good conductor

a) From table what can we infer?
Answer:
Distilled water does not allow the electric current to pass. Water in its pure form is a bad conductor of electricity. But when water contains salts or acids, it allows a passage of electric current and turns into a good conductor of electricity.

b) Do you understand why you are advised not to touch electric appliances with wet hands?
Answer:
Water with salts is a good conductor of electricity and the current flowing through househt d electric appliances is very high. Therefore we should never touch the electrical appliances with wet hands.

Activity – 4

Question 4.
Testing the effect of electric current on potato.
Take a potato. Cut into two halves and take one half of it. Construct tester with LED bulb. Insert two copper wires of the tester into the potato. Leaving some distance (around 1 cm) between them.

a) Dose the LED glow?
Answer:
Yes, the LED glows.
Leave the inserted wires for 20-30 minutes.

b) What do you observe the surface of the potato?
Answer:
A greenish blue spot is seen on the potato around the wire connected to the positive terminal of the battery.
But no such spot is seen around the other wire connected to the negative terminal. This greenish spot is due to chemical change in the potato.

c) What could be the cause behind this change?
Answer:
There is chemical change occurred in the potato.

d) Will other vegetables also show such an effect?
Answer:
Vegetable like carrot, beetroot, cucumber, radish, sweet potato show the chemical change there by the LED glows.

Activity – 5

Question 5.
Make your own cell.
(OR)
Draw the diagram of electrolytic cell and explain.
Collect two injection bottles. Cut two 5 cm long bits of thick copper wire. Use sandpaper to scrap about 1 cm of the coating off both ends of the wires.
Break open a exhausted dry cell and remove its outer metal covering (made of zinc). Cut two 2 mm wide and 5 cm long strips from this zinc plate. Insert the copper wires and zinc strips into the rubber caps of the injection bottles as shown in figure. Ensure that the copper wire and zinc strips do not touch each other.

Now take a wire and connect the copper wire of one bottle with the zinc plate of the other bottle. Fill both bottles with dilute sulphuric acid. Carefully close the bottles with the caps in which copper wires and zinc strips are inserted. Your cell is ready.
How will you test it?
Take an LED. Attach two wires to its two terminals. Touch the wire from one terminal to the zinc plate and the wire from other terminal to the copper wire. Did the LED light up ? If not, change the connections vice-versa. Did the LED glow ?
Repeat the above activity using lemon juice, tamarind juice and tomato juice one by one instead of sulphuric acid to make cells.

a) What other liquids can be used to make the cell?
Answer:
Acid solutions.

b) Will detergent solution be useful?
Answer:
Yes, it is useful.

c) How does above cell function?
Answer:
After a few seconds of immersion of zinc and copper into dilute sulphuric acid, zinc slowly begins to dissolve in the sulphuric acid. We can see bubbles getting formed on the copper rod.
The current is passed from copper rod to zinc rod. Here chemical energy is converted into electric energy by electrolysis method.

d) Can you compare this cell with dry cell?
Answer:
In the above cell electrolyte is dilute sulphuric acid whereas in dry cell ammonium chloride paste is electrolyte. The electrodes in above cell is copper and zinc, whereas in dry cell it is graphite (carbon) and zinc.

e) Which is good one? Why?
Answer:
Dry cell is better than ordinary Volta cell. The reason dry cell does not have any fluids. So it is easy to carry dry cell compared with volta cell. So dry cell is better than volta cell.

AP State Syllabus AP Board 8th Class English Textbook Solutions Chapter 1C A Letter to a Friend Textbook Questions and Answers.

AP State Syllabus 8th Class English Solutions Chapter 1C A Letter to a Friend

8th Class English Chapter 1C A Letter to a Friend Textbook Questions and Answers

Comprehension

Answer the following questions.

Question 1.
How did Suresh and Ramesh spend their time?
Answer:
Suresh and Ramesh enjoyed their childhood days in Manikonda village. Every day they played gilli-danda, hide and seek and kabaddi in their garden. They played in the moonlight. They enjoyed listening to the tales told by their grandpa. Thus they spent their time joyfully.

Question 2.
Why did Ramesh’s family move to the city?
Answer:
Ramesh’s family moved to the city as both Ramesh and his wife got jobs in the city (Hyderabad). They got jobs in software companies.

Question 3.
What change did you observe in Ramesh?
Answer:
Ramesh enjoyed his childhood days along with his friend Suresh in Manikonda village. There were so many unforgettable, joyous occasions in their childhood. They leisurely spent their time enjoying the beauty of the nature. But now he is not happy in city. He is annoyed at his busy city life. He is the man of disgust. Ramesh’s family members hardly find time to sit together. They have forgotten their family. They work like machines. They have missed the joy of the family, their company and many things in the busy life.

Question 4.
Do you think Ramesh is happy in the city? Why?
Answer:
No. I don’t think Ramesh is happy in the city. He thinks that his city life is very disgusting. Both Ramesh and his wife work at software companies. They don’t find any time to sit together. They are always busy. They work with computers, think like computers and live like computers. They have forgotten their family. Ramesh recalls all the joyous occasions he had during his childhood. He thinks that he has missed his relatives, the joy of the family, their company and many things in his busy life. He thinks that their flat is their world, just like a well for a frog.

Question 5.
What made Ramesh write to Suresh?
Answer:
As Ramesh had a meeting in his office, he didn’t meet his friend Suresh during his visit to Hyderabad the previous week. So, he wrote a letter apologizing for his not meeting Suresh.

Proect work

Observe any five families in your neighbourhood and draw your conclusions, ad¬vantages and disadvantages of living in a joint/nuclear family.
Answer:
I observed five families living in our neighbourhood. All the families are nuclear ones that consist of a man, his wife and their children.
In the present society the concept of the joint family system has been gradually breaking up. In its place a new system of nuclear family has aroused. I think both types of families have their own merits and demerits. The joint family system is a feature of agricultural societies. Collective living, collective planning and collective share in family wealth are the traditional features of the joint family. We can see the division of labour in a joint family. The joint family preserves the traditions, customs and values and passes them down to the next generations. With the passage of time, the joint family system has disintegrated, giving rise to the nuclear family system.
The nuclear family consists of a man, his wife and their children. Job opportunities available in the cities become the main cause of the disintegration of the joint family system. For a number of reasons, a joint family system doesn’t exist in the cities. There is a lack of living space in the cities. It is difficult to accommodate all the members of a joint family in a single house in the city. The cost of living is very high in the cities. The increasing individualistic and independent attitudes of grown up children give rise to the nuclear family system. Now, we see advantages and disadvantages of living in both the families.

Advantages of living in a ‘joint family’

1. Joint family helps the younger ones to develop social virtues like co-operation, sympathy, sacrifice, affection, selfless service, obedience and broad minded nature.
2. Each member of a joint family is given work according to his or her capacity. Hence, we find division of labour in a joint family.
3. There is more affection and love among family members.
4. Joint family affords ample leisure to its members.
5. Joint family acts as an agency of social control.
6. In the joint family the children the employed, the sick, the aged and the handicapped are well taken care of.
7. We find sharing of sorrowness in a joint family.

Disadvantages of living in a ‘joint family’

1. There is no privacy.
2. There is no financial independence.
3. There is a chance for disharmony due to generation gap.
4. There may be chances for conflict between males and females and the young and the old due to diverse temperaments.

Advantages of living in a ‘nuclear family’

1. Nuclear family provides more privacy.
2. The members of a nuclear family have financial independence and stability.
3. The members of a nuclear family have more freedom.
4. The members of a nuclear family find no stress and discomfort.

Disadvantages of living in a ‘nuclear family’

1. If both the parents are employees, they find no time to care for the children.
2. The members of a nuclear family feel insecure.
3. There may be extra expenses in a nuclear family.
4. The members of a nuclear family lose the support and experience of the elders.
5. There is no sharing of sorrows.

A Letter to a Friend Summary in English

Ramesh wrote this letter to his friend Suresh apologizing for his not meeting him during his visit to Hyderabad the previous week. Ramesh is a computer programmer at Microsoft, Hyderabad and his wife is a System Analyst at Dell, Hyderabad. He is annoyed at his busy city life. Both Ramesh and his wife work with computers, think like computers and live like computers. Their child always plays computer games never caring for anyone. Ramesh is very unhappy in the city. He recalled the memorable days of his childhood in his letter. Ramesh and Suresh enjoyed their childhood days in Manikonda village. They played together in their garden in the moonlight. Theirs was a big family. Their grandpa used to tell them tales. They played gill-danda, hide and seek and kabaddi. They went for swimming every Sunday. Ramesh remembered how their Padmanabhaiah Sir appreciated them when they got the first prize in District Science Fair. Their picnic to Koil Sagar and their tour of Srisailam were memorable. Ramesh couldn’t forget the roaring of the Krishna River at the dam. They enjoyed the festivals such as Dasara, Deepavali, etc. along with their uncle and aunt. Ramesh thought of his grandparents, uncles, aunts, brothers, sisters …. sometimes. He thought that they missed them all. They missed the joy of the family, their company and many things in their busy life. At present they are living in this unreal world. They have lost their real life.

A Letter to a Friend Glossary

faded (adj): pale

hardly (adv): almost never

disgusting (adj): extremely unpleasant

appreciated: understand the worth of

company (n): the fact of being with somebody else and not alone

affection (n): a feeling of liking for a person

AP State Syllabus AP Board 8th Class Physical Science Solutions Chapter 2 Friction Textbook Questions and Answers.

AP State Syllabus 8th Class Physical Science Solutions 2nd Lesson Friction

8th Class Physical Science 2nd Lesson Friction Textbook Questions and Answers

Improve Your Learning

Question 1.
Do you agree with the statement, “friction is both good and an evil”? Explain with examples.
Answer:
Yes, I agree with the statement friction is both good and an evil.
Explanation with examples.
a) Friction is good:

1. We cannot walk or run without friction.
2. We will not have any cars or bicycles because all of them move because of friction.
3. We cannot stop a moving car by applying brakes.
4. Carpenters will not be able to smoothen surfaces.
5. We will not able to hold any appliances such as hammer, soap, etc.
6. It will not possible to write with pen or pencil if there is no friction.
7. We could not fix nail on the wall.
8. No building could be constructed if there is no friction.

b) Friction is an evil: Friction is undesirable in machinery because it is responsible for overheating and wearing out of moving parts.

Question 2.
Explain why sportsmen use shoes with spikes.
Answer:
The spikes will increases the frictional force so that the sportsmen will get better grip on the floor.

Question 3.
Would it be easier or more difficult for you to walk on soapy water on the marble floor ? Why ?
Answer:
It is more difficult to walk on a marble floor having soapy water because soapy water acts as lubricant and decreases the friction.

Question 4.
What ways do you suggest to reduce friction?
Answer:
Ways of reducing friction:
a) Polishing: Decreasing irregularities of surface (or) smoothening the surface.
B) Lubricants: Using lubricants which will decrease the friction.
c) Ball bearings: Using ball bearings in machinery.
d) Steam lining: Automobiles and aeroplanes are steam lined to reduce the friction due to air.

Question 5.
What conditions are needed for static friction to come into play?
Answer:
The object should be at rest with respect to the surface upto certain limiting acceleration.

Question 6.
Give examples of practical application of static friction.
Answer:
The objects unable to move on their own is due to static friction between surfaces of object.
The practical application of static friction:

1. Construction of buildings.
2. Fixing nail in the wall.
3. A book placed in the shelf unable to change its position because it is unable to overcome frictional force.
4. We can write with pen or pencil due to static friction between finger and pen or pencil.
5. We will not able to hold appliances such as hammer.

Question 7.
Give examples showing the existence of sliding friction.
Answer:

1. A moving ball stops after sometime.
2. If we push an object it will stop after sometime.

Question 8.
Explain how can you measure frictional force?
Answer:
Tie a string around a brick. Pull the brick by a spring balance. When the brick just begins to move note down the reading on the spring balance that measure the force of friction between the surface of brick and the floor.

Question 9.
Explain how does lubrication reduce friction?
Answer:
When oil, grease or any other lubricants are applied between the moving parts of a machine, a thin layer formed between the moving surfaces so they do not directly rub against each other which will avoid the interlocking of irregularities. So lubrication reduce the friction.

Question 10.
What kinds of friction do you know?
Answer:
There are three types of friction.

1. Static friction
2. Sliding friction
3. Rolling friction

Question 11.
Explain why sliding friction is less than static friction.
Answer:
When an object starts sliding, the contact points on its surface do not get enough time to lock into the contact points on the floor. So the sliding friction is slightly less than the static friction.

Question 12.
Give examples of how is friction responsible for energy wastages? Give suggestions to reduce energy wastages by friction.
(OR)
How is friction responsible for energy loses give examples? Give suggestions to reduce energy loses by friction.
Answer:
As the friction increases the machinery parts develops heat there by efficiency of the machine decreases which leads lot of wastage of energy. The wastage of energy is due to overheating and wearing out of moving parts.
Suggestions:

1. To reduce friction between rotating shafts of machine tools we should have to use ball bearings.
2. Replacing wearing out of moving parts with new ones.

Question 13.
Seetha is observing a moving bus with the luggage on its top. As the bus is moving slowly there is change in the state of luggage on its top. But when the bus speeds up and starts moving fast, she noticed that the luggage on the top of the bus fell to the back of the bus. This raised many doubts in her mind regarding to the effect frictional force acting on the luggage as well as on the tyres of the bus. Can you guess the questions raised in her mind ? Write them.
Answer:

1. Why the bag is moving backward direction?
2. In which direction friction is acting on the bus as well as on the bag?
3. Whether frictional force effecting relative motion between bag and bus?
4. What happens to frictional force if we replace bag with other object?

Question 14.
Collect information either from internet or from books in library, about various new techniques being adopted by human beings to reduce energy losses due to friction. Prepare a note on that.
Answer:

1. We are using grease, oil, wax and other lubricants in the vehicles and machinery to reduce the friction.
2. Ball bearings are also used to reduce the friction.
3. Engine oil, gear oil, brake oil, clutch oil, etc. are used in vehicles.
4. Shock up oil is also used.
5. Levers are reducing the friction.
6. In trolleys and other vehicles which should carry heavy loads, the wheels are fixed.

Question 15.
Draw a free body diagram (FBD) to show various forces acting on a body which is sliding on an inclined plane.
Answer:

Question 16.
“Reducing friction to the lowest possible level in machine tools solves the problem of energy crisis and conserve biodiversity”. How do you support the statement? Explain.
Answer:
Yes, it will solve the problem of energy crisis and conserve biodiversity the reason is the majority of energy wasted in the form of heat energy due to friction. In order to develop more electrical energy we are depending on coal, petroleum, gas, nuclear energy and hydro electricity. The production of energy from these sources except hydroelectric power causing severe air pollution which are affecting animals and plants. So energy should be conserved by means of reducing friction.

8th Class Physical Science 2nd Lesson Friction InText Questions and Answers

Think and Discuss

8th Class Physical Science Textbook Page No. 22

Question 1.
Does friction oppose motion or relative motion of surfaces in contact? Discuss.
Answer:
Yes. Frictional force opposition or relative motion of surfaces in contact that’s why an object placed on a table unable to move on its own because it is unable to overcome friction similarly a moving ball comes to rest after sometime due to friction.

Question 2.
What observations and experiments can you cite to show the existence of friction?
Answer:

1. Push a ball on a sandy surface and on a concrete surface and the observation is on a concrete surface it travels more distance, the reason is the concrete surface apply less frictional force on the ball.
2. Apply vehicle brakes during summer and rainy seasons and the observation is during summer season the brakes works more efficiently than rainy season the reason is friction between tyre and brakes is less because rainy water acts as lubricant.

Question 3.
When do we speak of sliding friction?
Answer:
When applied force is more than the limit of static friction, the body starts to move then we speak about sliding friction.

8th Class Physical Science Textbook Page No. 25

Question 4.
Does friction act on a table resting on the floor?
Answer:
Yes, frictional force is acting on the table which is known as static friction.

Question 5.
If normal force is doubled ? What happens to friction? Discuss.
Answer:
Friction is directly proportional to normal force therefore friction will be doubled if the normal force is doubled.

Question 6.
Your friend says “friction depends on the area of contact?” How do you correct your friend through some experiments ?
Answer:
If is plain that the friction doesn’t depend on area of contact, I will explain this fact to my friend by fastening a brick kept horizontal to the surface to a spring balance and pulling it at the hook. The same experiment I do by keeping the brick vertical to the surface. In both the experiments we find no difference and I will make him to come to the conclusion that the friction depends on the normal force and not on weight of the object on the surface of contact.

Question 7.
“Friction is independent of weight, but depends on normal force between surfaces of contact where friction exists.” Do you agree with this statement? Discuss.
Answer:
Yes, I agree with this statement. The above experiment helps us to come to this conclusion. In both cases we used the same brick hence the weight doesn’t change. But when its positions were changed the frictions at each case is changed.

8th Class Physical Science Textbook Page No. 26

Question 8.
What important role does friction play in the life of human beings and animals?
Answer:

1. Without friction human beings and animals unable to walk or run on any surface.
2. Without friction they unable to hold any appliances.
3. It will not be possible to write with pen or pencil if there is no friction.
4. We cannot stop car or cycle by applying brakes.
5. No building is constructed if there is no friction.
6. Carpenters will not be able to smoothen surfaces.

Question 9.
Why is friction important for transport?
Answer:
Threading in tyres provide friction for cars or buses so that they can move safely therefore friction is important for transport.

8th Class Physical Science Textbook Page No. 28

Question 10.
Can we reduce friction to zero? Explain.
Answer:
No, we cannot. Friction can never be entirely eliminated because no surface is perfectly smooth and some irregularities are always there.

Question 11.
What purposes are served by bearings in machines? Explain with daily life situations.
Answer:
The ball bearings are used to reduce friction between rotating shafts of machine tools and it increases the efficiency of machines.

8th Class Physical Science 2nd Lesson Friction Activities

Activity – 1
Question 1.
Identifying forces acting on a body and effect of frictional force.
Gently push a book on a horizontal floor. You may observe that the book acquires certain speed in the direction of push. However, the speed of the book gradually decreases and after sometime it stops.

a) Why does the book stop after covering some distance?
Answer:
Some opposing force is acting to its motion.

b) Is the book moving with uniform speed?
Answer:
No, its speed decreases gradually.

c) Why does the speed of the book change gradually?
Answer:
Some net force is acting opposite direction to its motion.

d) How many forces act on the book when it is pushed on the floor?
Answer:
Two forces act on the vertical direction. They are

1. Weight of the book or gravitational force acting vertically down.
2. Normal force or reaction force applied by the floor vertically up.
3. Forces acting horizontal direction.

e) What are the forces acting on the book in the horizontal direction?
Answer:

1. Muscular force applied by us.
2. Opposing force acting opposite to motion of book.

f) What is the net force acting in the horizontal direction?
Answer:
The net force is the difference between muscular force and opposing force to the motion of book.

Lab Activity

Write an activity to understand friction and static friction.
(OR)
Conduct an experiment to understand the nature of friction and the concept of static friction.
Answer:
Aim: To understand the nature of friction and the concept of static friction.
Materials required: Toy trolley, small wooden block, inextensible string, weight hanger, weights, pulley and table.
Procedure: Take a small toy trolley and keep a small wooden block on it as in the figure. Tie an inextensible string to the trolley and pass it over a pulley. And other end of the string is fixed to weight hanger. Take a small weight and keep it on weight hanger and observe the changes in motions of block and trolley.

Observation:
The trolley with block moves towards left with an acceleration. The block is not with respect to the surface of trolley, but it is in motion with respect to surface e table. The force of friction of the trolley acts on the direction of motion.
We increase trolley’s acceleration gradually by increasing the weight on the hanger at certain limiting weight the block comes in motion in the reverse direction.
That means now there exists relative motion between the surface of the trolley and block.
Result:
The force which opposes the relative motion of the two surfaces of bodies which are in contact is called frictional force.
The block is at rest relative to surface of the trolley upto a certain limiting acceleration. The friction exists at that stage is called static friction.

Activity – 2

Question 2.
Observing the variation of friction.
Push a heavy box which is kept on a floor. The box does not move. Now increase the applied force until the box moves.

a) Why does the box does not move at first?
Answer:
The applied force is less than frictional force (static friction).

b) When does the box tends to move?
Answer:
When the applied force is more than static friction.

Activity – 3

Question 3.
Effect of roughness on frictional force.
Set up an inclined plane on the horizontal floor. Use a wooden board as inclined plane. Put a mark at any point
‘A’. Now let a pencil cell or ball is move down from this point. Note down the distance travelled by the ball from the bottom of the inclined plane to point where it comes to a stop.

Now, spread a cloth over the floor. Try again with ball and note down the distance.

a) What are your observations from these experiments?
Answer:
The distance covered by ball in the two cases are different.

b) In which case is the distance covered maximum?
Answer:
When there is no cloth on the floor.

c) In which case is the distance covered minimum?
Answer:
When cloth is spread over the floor.

d) Why is the distance covered by the pencil cell different on different surfaces?
Answer:
Because, the friction offered by different surfaces are different.

e) If the cloth is replaced with white marble surface or glass surface, what will be your prediction about the distance covered by the pencil cell?
Answer:
The pencil cell covers more distance.

Activity – 4

Question 4.
Effect of area of contact on frictional force.
Tie a string around a wooden block and pull the wooden block by using a spring balance.

Pull it to make a move in the brick. Note down the readings of spring balance when the brick just begins to move.
a) How many forces are acting on the wooden block in the horizontal direction?
Answer:
Two forces are acting in the horizontal direction.

1. Force of friction,
2. Force applied by us.

Now turn the wooden block upright and measure the friction by doing the same experiment using the reading of the spring balance.

b) How does the frictional force vary with the change in the area of contact?
Answer:

The frictional force appears the same in both cases irrespective of area of contact. So it is independent of area of contact.

Activity – 5

Question 5.
Effect of normal force on friction.
Keep a wooden block on the horizontal floor and pull it with the spring balance attached to it and measure the frictional force.
Now put another wooden block over the brick tied to the spring balance or press it vertically with your hand and measure the frictional force.
a) Is there any difference between frictional forces in two cases? If yes, why?
Answer:
Yes, the reason is when we add a wooden block to the existing wooden block or apply force by pressing vertically, the normal force increases and hence we find increase in frictional force.

b) What is the relationship between friction and normal force?
Answer:
Friction is proportional to the normal force, i.e., friction °c normal force.

Activity – 6

Question 6.
Friction produces heat.
a) Rub your palms against each other for a few minutes. How do you feel?
Answer:

They became hot.

b) Strike a match stick against the rough surface of match box. What happens?
Answer:
The match stick catches fire.

c) What is your observation in this activity?
Answer:
Temperature of surfaces increases due to friction.

d) What is your conclusion on this activity?
Answer:
Friction can also produce heat.

e) You have probably heard that space craft returning to the earth have to be protected by a heat shield covering it. Find out why. What is the material used as heat shield?
Answer:

Space craft returning earth have to be protected by a heat shield covering it in order to protect it from atmospheric friction.
The material generally used is insulator of heat.

Activity – 7

Question 7.
How to increase Motion?
Take a spoon and hold its head (broader portion) in the left hand and hold the mid portion of the spoon by the right hand and pull it towards the other end of the spoon.
a) What do you notice?
Answer:
We unable to pull the spoon.
Now dip your right hand fingers in water, do it again as said above.

b) In which case is it easy to pull? Why?
Answer:
In second case it is easy to pull because water decreases the friction.

c) Have you ever thought why the sole of your shoes is grooved as shown in figure?
Answer:

It will provide shoes better grip on the floor so that we can move safely.

d) Cars, trucks and bulldozers tyres are threaded. Why?
Answer:

To provide them better grip on the floor.

e) Why do you need to change the tyres when it’s threading is worn out?
Answer:
If we does not change the tyre then the frictional force decreases and the vehicle may skid.
Play carrom board without powder and then play with fine powder sprinkled on board.

f) In which case is the movement of the striker and the coins easy? Why?
Answer:
When fine powder sprinkled on board, it will decrease the friction between coin and board surface.

g) Why do we pour a few drops of oil on the hinges of a door?
Answer:
It will decrease the friction and provide better movement of door.

h) Why do we use grease between the moving parts of motor vehicles?
Answer:
To reduce friction in order to increase efficiency.

Activity – 8

Question 8.
Effect of rollers on friction.
Pull a suitcase without rollers and pull a suitcase which has rollers.

a) In which case is the pulling easy? Why?
Answer:
It is easy to pull when suitcase has rollers.
Try to push a book lying on the table. Now place the book on two to three pencils or pens without caps. Push the book again.

b) What do you notice ? In which case is it easy to pull the book? Why?
Answer:

In the second case it is easy to pull the book. The reason is it is always easier to roll a body than to slide it over a surface.

Activity – 9

Question 9.
Understanding the principle of ball bearings.
Take two lids and rotate them by putting one on the top of the other.

a) What do you observe?
Answer:
It is difficult to rotate them.
Now place three to four marbles on one lid and place the other lid on the top of the marble. Now try to rotate the top lid.

b) What do you observe?
Answer:
Now we can easily rotate the lid because rolling friction is less than sliding friction.

c) What is your conclusion on the principle of ball bearings?
Answer:
We can easily rotate top lid by placing marbles between the lids. This is the principle of ball bearings.

Activity – 10

Question 10.
Observing fluid friction.
Take a glass of water and stir it with a spoon. You know that water whirls around an axis. Stop stirring and see what happens.

The whirling speed of water gradually decreases and after some – time, the water stops whirling and comes to a stable state

a) Which force is responsible for stopping the rotation of the water.
Answer:
The frictional forces between the liquid layers or between the liquid surfaces that is in contact with glass surface.

Activity – 11

Question 11.
Identifying factors influencing the fluid friction.
Take a tub of water. Try to move your hand in water in the direction of stretched fingers i.e., up and down. Now try to move your hand in the direction perpendicular to the plane of the hand i.e., to and fro.

a) In which orientation of your hand, do you experience more drag? Why?
Answer:
We experience more drag in the direction of stretched fingers. The frictional force on an object in a fluid depends on its speed with respect to fluid and on the shape of the object and nature of the fluid.
When objects move through fluids, they have to overcome friction acting on them. So objects are given special shapes to minimise fluid friction.

b) Where do you think scientists get hint for these special shapes?
Answer:
From nature i.e., from birds and fishes, which have to move about in fluids all the time.

c) Do you find any similarity in the shape of an aeroplane and a bird? Why?
Answer:
Yes. The shape of aeroplane designed as bird in order to reduce fluid friction.

AP State Syllabus AP Board 8th Class Biology Solutions Chapter 7 Different Ecosystems Textbook Questions and Answers.

AP State Syllabus 8th Class Biology Solutions 7th Lesson Different Ecosystems

8th Class Biology 7th Lesson Different Ecosystems Textbook Questions and Answers

Improve Your Learning

Question 1.
Define an ecosystem. Explain it with a suitable example.
Answer:

1. An ecosystem can be defined as a functional unit of nature, where living organisms interact among themselves and also with the surrounding physical environment.
2. For example, Mangroves are one of the most productive ecosystem on earth, deriving nourishment from terrestrial fresh water and tidal salt water.
3. Coringa mangrove is situated south of Kakinada Bay and is about 150 km south of Visakhapatnam.
4. It is named after the river coringa. Coringa mangroves receives fresh water from coringa and Gaderu rivers and salt waters from Kakinada Bay.
5. Biotic components in coringa:
   Producers: Mangrove, Spirogyra, Euglena, Oscilatoria, Blue Green Algae, Ulothrix etc.
   Consumers: Shrimp, crab, hydra, protozoans, mussel, snails, turtle, daphnia, brittle word, tube worm etc.
   Decomposers: Detritus feeding bacteria etc.
6. Abiotic components: Salt and fresh water, air, sunlight, soil, etc.

Question 2.
Explain how diversity of living organisms helps in enriching any ecosystem.
Answer:

1. The existence of the ecosystem depends on the continued survival of the organisms in the ecosystem.
2. All organisms require energy for growth, reproduction and survival.
3. This energy is obtained by the organisms from the food they consume.
4. Plants are the producers producing food in any ecosystem. The animals present in the ecosystem are consumers as they consume food from plants.
5. Some of the organisms in the ecosystem such as bacteria and fungi, obtained their nutritional requirements by decomposing the dead bodies of both producers and consumers.
6. They retain nutrients to the soil for the plants to use. As the cycle begins again.
7. Like this diversity of living organisms helps in enriching any ecosystem.

Question 3.
What happens when two animals having similar habits share one ecosystem?
Answer:
When two animals having similar habits, sharing one ecosystem , only the stronger and better equipped animal can survive, while the weaker one die or eliminated from the ecosystem. This is called ‘Survival of the fittest’.

Question 4.
What is the difference between habitat and ecosystem?
Answer:
Habitat is the natural living place of an organism or a group of organisms. Land and water are the major habitates.
An ecosystem is a Natural unit and has both Abiotic and biotic components, which interact and influence each other.

Question 5.
Who am I?
1. I am the base of food chain.
Answer:
Green plants.
2. I depend on plants for food.
Answer:
Consumers (Herbivorous Animals)
3. I break down the remains of dead plants and animals.
Answer:
Decomposers.
Ex: Bacteria, Fungi.

Question 6.
Which of the following is producer and why?
а) fox b) fungus c) chicken d) grass.
Answer:

1. Grass is the producer.
2. All green plants produce food materials with the help of carbondioxide and water in the presence of sunlight. So plants are called producers.
3. As grass is the green plant and produce food for other animals, it is called producer.

Question 7.
What do you understand by food web? Describe your own food web with the help of diagrammatic representation.
Answer:

1. A food web consists of several interlinked food chains and each organism in the food web will be a member of more than one food chain.
2. For example rats and insects eat seeds and other plant parts. As their food.
3. Insects are eaten by frogs and lizards.
4. Rats and frogs are eaten by snakes.
5. Lizards and snakes are eaten by birds.
6. Birds are eaten by fox, wolves. These are eaten by tigers and lions.
7. Thus a single plant or an animal may become food for more than one animal.
8. Similiarly an animal may consume more than one type of food depending on its taste and availability in the ecosystem.
9. Thus each organism in an ecosystem may be a member of more than one food chain.
10. When we looked at these relationships between various organisms for food in the ecosystem, it appears that several food chains are interlinked with each other forming a food web.

FOOD WEB

Question 8.
An ecosystem that had mice. What happens if more cats were added to it?
Answer:

1. In an ecosystem if the mice and the cats were existing equally, smooth balance would be maintained. When reproduction took place in these animals, generations would be continued then the ecosystem would be maintained healthy.
2. When more cats were added in that ecosystem all the mice would be eaten away by the cats it leads to the end of mice population.
3. Because of lack of food, the cats, either have to leave the ecosystem or they die.
4. If there is no continuity of the animals, the ecosystem would be destroyed.

Question 9.
List out producers (plants, bushes, trees), consumers (herbivores and carnivores) and decomposers that you observed in your agriculture field or school garden.
Answer:
Producers:
Plants – Grass plants, creepers like pumpkin, bottlegourd, etc.
Bushes – Rose, Jasmine, chrysanthemum, marigold.
Trees – Palm, coconut, mango, drumstick, lemon, sweet lemon, guava.
Consumers:
Herbivores – Goat, sheep, buffalo, ox, rats, butterflies, etc.
Carnivores – Crow, dogs, snakes, frogs, lizards.
Decomposers – Fungi (mushroom), Bacteria.

Question 10.
In grassland ecosystem, rabbit eats only plants. They eat plants faster than the plants can grow back. What must happen to bring the ecosystem into balance?
Answer:
The animals like fox, wolves, tigers, etc. which feed on rabbits will be introduced in that grass land ecosystem, then the rabbits will be controlled by them. Thus the ecosystem will comes into balance.

Question 11.
Plant, Tiger, Rabbit, Fox, Hawk.
Did you find any connection among the above list of things. If we remove Rabbit from the list what will happen?
Answer:

1. Plant, tiger, rabbit, fox, hawk these are the animals living in an ecosystem and are interdepending one on the other, and maintaining a food web – Plants → Rabbit → Hawk → Fox → Tiger.
2. A delicate balance is seen in nature between members of different species.
3. Any disturbance in this balance affects the organisms in a food web.
4. If we remove rabbit from the list the other animals like tiger, fox, hawk which are depending one on the other for food will die because of no food.
5. All the organisms, big or small, have right to live on this planet as man. We should respect this and allow other organisms to live and share the wealth of this planet.
6. “LIVE AND LET LIVE” should become our motto.

Question 12.
What do you understand by interdependency of animals and plants ? How do you appreciate ?
Answer:

1. An ecosystem is made up of groups of living things and their environments.
   
2. Living things like plants, animals and microorganisms are known as biotic components and others like soil, water, sunlight etc are called as abiotic components of the ecosystem.
3. All these organisms live together and interact with one another in many ways.
4. There is a feeding relationship between plants and animals. Along with this an interdependence between plants and animals for space, reproduction, shelter, etc.
5. All organisms in an ecosystem derive energy from food to live.
6. The sun is the main source of energy for all living things.
7. Plants being autotrophic, trap this energy through a process called photosynthesis and produce food to all living organisms. They are known as Primary producers.
8. Animals as they can not prepare food, they consume plants directly or indirectly and called consumers.
9. Living organisms like fungi and bacteria which are called decomposers, decay and decompose the dead animals of producers and consumers, and valuable nutrients to the soil for plants to use, as the cycle begins again.
10. A delicate balance is seen in nature between plants and animals by interdependence one to the other for thousands of years, which is unreachable to the human brain.

8th Class Biology 7th Lesson Different Ecosystems InText Questions and Answers

Question 1.
What is a Habitat?
Answer:

1. The dwelling place for plants and animals is called habitat.
2. One habitat shared by different types of plants and animals.
3. Try to add more such points to your list.
4. The natural home for plants and animals is called a habitat.
5. Habitat is the environment of an animal or plant.
6. Habitat is a suitable place for plants and animals to live.
7. Habitat is the origin for plants and animals.

Question 2.
Draw the diagram of Interdependence between the biotic components and answer the following questions.
Answer:
Interdependence between the biotic components:

1. What do the arrows in the figure indicate?
Answer:
The animals are depending one on the other for food.

2. Trace the path from grass to tiger. You may trace out other paths as well.
Answer:
Grass → grass hopper → frog → snake.
Carrot and grass → rabbit → fox → tiger
Plants → deer → bear → tiger
Seeds → squirrel → eagle → tiger

3. On how many organisms is rabbit dependent? Write their names.
Answer:
Carrot, grass.

4. How many organisms depend on rabbit? Write their names.
Answer:
Snake, fox, eagle, tiger.

5. Where do plants get their food from?
Answer:
Plants are autotrophs they can prepare their food from carbondioxide and water, in the presence of sunlight.

6. What other things do animals need for their survival?
Answer:
Abiotic components like soil, water, sunlight, etc.

8th Class Biology 7th Lesson Different Ecosystems Activities

Activity – 1

Lab Activity
Answer:
Aim: Study an ecosystem at your school/ home garden to understand it’s structure. Material Required : Measuring tape string, small sticks, hand lens, hand towel.
Procedure: To know about structure of the ecosystem we have to follow the following procedure.

1. Use the tape to measure a square area that is one meter long and one meter wide. It can be on grass, bare dirt or side wall.
2. Mark the edges of the square with the help of string/chalk.
3. Observe the study area (that has been marked). Look for the plants and animals that live there. Use the hand lens.
4. Record all the living organisms you see. You can even dig to go deeper to find out other living organisms that may be present there.

Observation / Findings: We find –

1. Plants like grass, herbs, shrubs, guava, neem and creepers.
2. Insects like ants, grass hoppers, butterflies, mosquitoes, houseflies, locusts, etc.
3. Animals like cat, dog, buffalo, frog, lizards, garden lizards, snake.
4. Mushroom, algae.
5. Deeper layers of soil we find earth worm, leech, rats, bandicoots, rabbits, etc.
6. Birds like crow, parrot, mynah, etc.

Discussion:
1. What living things did you find in your study area? Try to count them if possible.
Answer:
Grass, creepers, shrubs, herbs, trees, herbivores, carnivores, fungi.
2. Which kind of living thing was most common in your study area?
Answer:
Plants.
3. How was your study area different from those of other student groups?
Answer:
Living conditions, food, animals and plants are different.
4. Other than the living organisms what other things can you record from your study area?
Answer:
Soil, water, sunlight (temperature) are recorded.

Activity – 2

Question 2.
Observe the food web given below figure.

Answer:
The diagram showing food web.
Now answer the following Questions.
1. Which are the producers in the food web?
Answer:
Grass, rice plants, maize, bushes.
2. Which are consumers?
Answer:
Fish, frog, birds, rats, rabbit, deer, tadpole, larva ,sheep, cat, fox, tiger, crane, eagle, snake, owl, peacock, insects, lion.
3. Where does the food web start from?
Answer:
Food web starts from green plants.
4. Name the organism where the food web ends.
Answer:
Crane, eagle, owl, peacock, lion.
5. What happens when plants and animals die in a food web?
Answer:
When plants and animals die, they are decayed and decomposed by Decomposers like bacteria and fungi. They return nutrients to the soil for plants to use, as the cycle begin again. This is the reason ‘Decomposers are also called as recyclers.

Activity – 3

Question 3.
Collect the information forests of Andhra Pradesh and write the flora and fauna and fill up the following table:
Answer:
Forests of Andhra Pradesh

Name of the Forest – Kondapalli Reserve Forest

Investigations:

1. Do all the forest have same type of vegetation?
Answer:
No, there are mainly trees that show much species diversity and greater degrees stratification.
2. Are producers afforest ecosystem higher than its consumers?
Answer:
Trees are higher than consumers, besides trees shrubs and ground vegetation also there.
3. Do all the forests have same type of animals?
Answer:
No, the availability of food and environment different type of animals are present in different forest.

AP State Syllabus AP Board 8th Class Physical Science Solutions Chapter 5 Metals and Non-Metals Textbook Questions and Answers.

AP State Syllabus 8th Class Physical Science Solutions 5th Lesson Metals and Non-Metals

8th Class Physical Science 5th Lesson Metals and Non-Metals Textbook Questions and Answers

Improve Your Learning

Question 1.
Explain the physical properties of metals with suitable examples.
(OR)
Explain briefly the physical properties of metals.
Answer:
Physical properties of metals:

1. Lustrous:
   When we rub the surface of metals with sand paper they will shine. This property is called lustrous, e.g.: Iron, zinc etc.
2. Sonority:
   When we hit the metal surface they give a ringing sound is called sonority, e.g.: Iron, copper etc.
3. Malleability:
   Metals can be flattened into thin sheets. The property of flattening metals into thin sheets is called malleability, e.g.: Silver, Iron, copper.
4. Ductility:
   Metals can be drawn into wires.
   The property of drawing a metal to make fine wire is called ductility, e.g.: Silver, gold.
5. Electric conductivity:
   Electricity can be easily pass through metals. So they are called good conductors of electricity.
   e.g.: Silver, copper, iron.
6. Conductivity of heat:
   Metal absorbs heat quite easily. They are good conductors of heat, e.g.: Copper, iron.

Question 2.
You are given two samples. How do you distinguish which is metal and which is non-metal?
Answer:

1. By physical properties, generally we can judge whether the given sample is metal or non-metal that is metals are hard. They are lustrous, sonorous, malleable, ductile and good conductors of heat and electricity.
2. Generally metal sample react with water and non-metal sample does not react with water.
3. Generally metal sample react with acid and produce hydrogen gas whereas non-metal samples does not react with acid.

Question 3.
Which metals are used in making jewellery? Why?
Answer:
Generally we use metals like gold, silver and copper for making jewellery due to their high ductility and lustrous surface.

Question 4.
Which substance liberate hydrogen when react with metals?
Answer:
Generally acids react with metals and liberate hydrogen gas. Water also react with some metals and liberate hydrogen gas.

Question 5.
In a chemical reaction iron is unable to displace zinc from zinc sulphate. Why?
Answer:
Zinc is more reactive than iron. A less reactive metal cannot displace a more reactive metal from its salt solution. So iron unable to displace zinc from zinc sulphate.

Question 6.
Why cooking pans do not have metal handles?
Answer:
Metals are good conductors of heat. So they gain heat easily. So in order to avoid the burning of our palms, the handles of cooking pans made of heat resist material such as plastic.

Question 7.
Sulphur dioxide is
A) basic oxide
B) acidic oxide
C) neutral oxide
D) amphoteric oxide
Answer:
B) acidic oxide

Question 8.
Match the following.
Group – A                                             Group – B
1. Making into thin sheets        ( )        A) Ductility
2. Shining materials                  ( )        B) Conductivity
3. Making into wires                 ( )        C) Sonority
4. Transmission of heat            ( )        D) Lustrous
5. Making ringing sound          ( )         E) Malleability
Answer:
1. E
2. D
3. A
4. B
5. C

Question 9.
Which gas makes a ‘pop’ sound if exposed to lighted matchstick?
Answer:
Hydrogen gas makes a pop sound when it is exposed to a lighted matchstick.

Question 10.
Why are bells made up of metals instead of wood
Answer:
Metals have sonority property that means they make ringing sound when we hit them with a hammer. Where wood does not give ringing sound when it is hit with a hammer. So bells are made up of metals instead of wood.

Question 11.
Imagine the human life without metals, write briefly about the consequences.
Answer:

1. There would not be any utensil for cooking.
2. There would not be trains, buses, aeroplanes for travelling.
3. There would be no almirahs, no school bells, no agricultural material, no electrical appliances, no automobiles, no satellites, no machinery and no decorative material. So everything in life directly or indirectly depends upon metals. So we cannot imagine a life without metals.

Question 12.
After completion of metals and non-metals chapter, Raheem understood that metals are hard and non-metals are soft. During the discussion with his brother he came to know that diamond is a hardest material and it is a non-metal. Similarly mercury is a soft material and it is a metal. These findings from the discussion raised some questions in Raheem’s mind. Can you guess those questions? Write them.
Answer:
The doubts arised in Raheem’s mind are

1. If diamond is hard how it behaves like a non-metal?
2. If mercury is soft material how it acts as metal?
3. What are the properties which actually decide whether the given material is either metal or non-metal?

Question 13.
Discuss the acidic and basic nature of the metals and non-metals with suitable experiments.
Answer:
Take a small strip of magnesium and burn it. It forms white ashes of magnesium oxide collect the ashes of magnesium and add some distilled water to it. Test the solution with red and blue litmus papers. Note the colour changes. The solution turns red litmus into blue. It indicates given solution is basic. So metallic oxides are basic in nature.
Take a small amount of powdered sulphur in a deflagrating spoon and heat it. As soon as sulphur starts burning, introduce the spoon into a gas jar or tumbler. Cover the tumbler with lid to ensure that the gas produced does not escape. The gas formed is sulphur dioxide. Remove the spoon after some time but try to keep the jar covered. Add a small quantity of water into the tumbler and quickly replace the lid. Shake the tumbler well. Check the solution with red and blue litmus paper. The solution turns blue litmus into red. It indicates the solution is acidic. So non-metallic oxides are acidic in nature.

Question 14.
How do you appreciate wide range utility of aluminium right from utensils to space craft?
Answer:
Aluminium is essential part of our life. Aluminium foil is used on inner packing of food materials and toffees. Aluminium and copper mixture is used in currency coins, medals and statues. Aluminium is used in electrical appliances, automobiles, satellites, space crafts, aeroplanes, cooking utensils, machinery, decorative materials. This indicates wherever we go we observe articles made up of aluminium. So we require aluminium for better living.

Question 15.
How is malleability of metals used in our daily life
Answer:
Metals can be flattened into sheets is called malleability. Due to this metals can be made into different shapes like railway coaches, railway tracks, cooking utensils, etc. So malleability of metals is extremely useful in daily life.

Question 16.
Dumping of waste material made up of metals and non-metals leads to environment pollution. Do you support the statement? Give your justification with suitable examples.
Answer:
Soil samples analyzed from location adjacent and with in deposite show high level of heavy metals in particular lead, mercury, cadmium, copper and chromium. In which lead and mercury are extremely harmful to environment as well as mankind. After medical evaluation the adolescents living and children living near dump site had high incidence of diseases that are associated with high exposure levels to these metal pollutants. So waste material made of metals and non-metals leads to environmental pollution. Some more examples are burning of sulphur forms sulphur dioxide and sulphur trioxide, which is a cause for acid rain and soil corrosion. In complete burning of carbon leads to release of poisonous carbon monoxide.

8th Class Physical Science 5th Lesson Metals and Non-Metals InText Questions and Answers

Think and Discuss

8th Class Physical Science Textbook Page No. 68

Question 1.
How will you close the circuit using sulphur, carbon or iodine? They may be in powder form. Try to tightly pack the powder in a straw and use it. Think of other ways!
Answer:
Circuit will not be completed by using non-metals like sulphur, carbon or iodine because they are bad conductors of electricity. So by packing the powder will not complete the circuit. There is no other by using which we can complete the circuit by using a non-metal.

Try This

8th Class Physical Science Textbook Page No. 74

Question 1.
Recall the names of the some of the laboratory acids and bases that you know. Write down their names in table and identify metal/non-metal present in them, which form oxides when react with oxygen. Take the help of your teacher.
Answer:

Name of the base	Metal present in it	Name of the acid	Non-metal present in it
Calcium hydroxide (Ca(OH)2)	Calcium (Ca)	Sulphuric acid (H2SO4>	Sulphur (S)
Sodium hydroxide (NaOH)	Sodium (Na)	Hydrochloric acid (HCl)	Chlorine (Cl)
Magnesium hydroxide (Mg(OH)2)	Magnesium (Mg)	Nitric acid (HNO3)	Nitrogen (N)
Zinc hydroxide (Zn(OH2)	Zinc (Zn)	Phosphoric acid (H3PO4)	Phosphorus(P)
Sodium hydroxide (NaOH)	Sodium (Na)	Sulphurus acid (H2SO3)	Sulphur (S)
Cupric hydroxide (Cu(OH)2)	Copper (Cu)	Carbonic acid (H2CO3)	Carbon (C)

Question 2.
Have you seen a periodic table?
Answer:
Yes.

Question 3.
Try to find the metals and non-metals that you come across in the chapter on the periodic table.
Answer:
Metals               Non-metals
1) Zinc               1) Sulphur
2) Copper          2) Chlorine
3) Iron               3) Nitrogen
4) Potassium     4) Carbon
5) Sodium         5) Phosphorus
6) Gold
7) Silver
8) Magnesium
9) Calcium
10) Aluminium

8th Class Physical Science 5th Lesson Metals and Non-Metals Activities

Activity – 1

Question 1.
Observing appearance and colour of some materials:
Observe the appearance of your samples. Look at their colour. Decide whether they appear shining or dull and record your observations in table. If the surface seems dirty, clean it with sand paper.

Sample	Appearance Shining / not shining	Colour
Iron	shining	grey
Zinc	shining	pale green
Copper	shining	red
Sulphur	not shining	yellow
Aluminium	shining	silver white
Carbon	not shining	black
Magnesium	shining	silver white
Iodine	shining	black

a) Which of the samples did not shine even after you cleaned them with sand paper?
Answer:
Sulphur, carbon.

b) Generally metals are lustrous. Do all lustrous materials are metals?
Answer:
No. Some may be non-metals, e.g.: Iodine

c) We all know that mirror is lustrous. Can a mirror be called metal?
Answer:
No. Several properties required to decide if a given material is metal or not.

Activity – 2

Question 2.
Listening the sound produced by some material:

a) Drop a piece of coal on the floor and listen the sound.
Do you think coal is sonorous?
Answer:
No.

b) Take the pieces of zinc, copper, aluminium, magnesium and tightly packed packets of sulphur, carbon and iodine. Drop them one by one, on a hard surface. Listen carefully to the sound produced and record your observation in table.
Answer:

Material sample that	Material sample that
produce sound	do not produce sound
Zinc	Sulphur
Copper	Carbon
Aluminium	Iodine
	Magnesium

c) What similarity do you notice among materials which produce sound?
Answer:
All of them are metals.

d) Which property of metals first attracted the attention of human beings?
Answer:
Metals had the advantage of not just being harder but they could be heated in a fire and moulded or cast into different shapes. This property of metals first attracted the attention of human beings.

e) Do you bring a similar change in the shape of a clay material by beating it?
Answer: Yes, we bring similar change in the shape of a clay material by beating it.

Activity – 3

Question 3.
Identifying malleability of material:
Take a hammer and beat the material samples which are used in Activity-2 and observe the changes in material samples. Record your observations in the table.
Answer:

Observing the change	Name of sample
Flattens	Iron, zinc, copper, aluminium
Breaks/ converts into powder	Magnesium, sulphur, carbon, iodine
No change	—

Some of the samples like zinc, copper are flattened whereas some materials such as carbon, iodine broken into pieces.
The materials which can be flattened into thin sheets are called malleable materials.
Ductility:
We use wires in different situations in our daily life. Look at the samples given in the table.

a) Have you ever seen the wires made up of materials mentioned in the above table?
Answer:
Yes. I have seen the wires made of iron, copper, aluminium.

b) What is the property of drawing material to make wire is called?
Answer:
Ductility.

Activity – 4

Question 4.
Identifying electric conductivity of a material:
Arrange an electric circuit with a battery and bulb. Close the circuit using an iron nail, as shown in figure. Observe whether the bulb glows or not. Record your observations in table. Repeat the same experiment using the other samples and record your observations in the same table.

Sample	Can we convert it into wires
Iron	Yes
Zinc	Yes
Copper	Yes
Sulphur	No
Aluminium	Yes
Carbon	No
Magnesium	No
Iodine	No

a) Do all the samples allow the bulb to glow?
Answer:
No. Materials like iron, zinc, copper allows bulb to glow.

b) What is name given to these material which allows electricity to pass them and make to bulb to glow are called?
Answer:
They are called conductors.

c) Give examples for good conductors of electricity?
Answer:
Copper, iron, aluminium

d) Talk to an electrician. Look at the handles of his tools. Are the handles made of the same materials? If not why?
Answer:
No. The handles of his tools are made of electrical insulating material in order to avoid electrical shock.

Activity – 5

Question 5.
Observing heat conduction by metals:

Take an iron rod. Stick pins on it with the help of wax. Now fix the rod to a stand as shown in figure. Heat one end of the rod with a spirit lamp and see how the pins fall off?

a) Why did the pins fall off from iron rod?
Answer:
Iron rod gains heat from spirit lamp.

b) Pin of which end fell off first?
Answer:
The pin which is near to spirit lamp falls first.

c) What could be the reason for this?
Answer:
The pin falls off because of heat supplied to the iron rod and makes the wax to melt at one end. The wax closer to the flame melted first and the pin falls off. Then the other pins falls. This activity shows that heat moves from one end of the rod to the other. This property of a material is known as conductivity of heat.

d) Go back to the list of samples. On the basis of all the activities carried out, fill the following table.
Answer:

Lab Activity

Conduct an experiment to know the reaction of oxygen with metals and non-metals.
Answer:
Aim: To know reaction of oxygen with metals and non-metals.
Materials required: One metal sample (Magnesium) and one non-metal sample (Sulphur), spirit lamp or Bunsen burner and litmus paper, etc.
Procedure:
Take a small strip of magnesium and burn it. It burns brilliantly and produce white ashes of magnesium oxide due to reaction between magnesium and oxygen. Collect the ashes of magnesium and add some distilled water to it. Test the solution with red and blue litmus papers. Note the changes in table.

Take a small amount of powdered sulphur in a deflagrating spoon and heat it. Sulphur starts burning and forms sulphur dioxide. Introduce the spoon into a jar and cover the jar with a lid to ensure that the gas produced does not escape. Add small quantity of water into the jar quickly replace the lid. Shake the jar well. Check the solution with blue and red litmus papers. Record the changes in table.

Sample	Physical Appearance before reaction	Physical Appearance after reaction	Effect of Litmus Paper
Magnesium	Silver white sheet	White ash	Turns red litmus into blue
Sulphur	Yellow powder	Colourless gas	Turns blue litmus into red

From the table we can observe metallic oxide solutions are basic in nature whereas non metallic oxide solutions are acidic in nature.

Activity – 6

Question 6.
Experiment about reaction of metals with water.
Answer:
Take a 500 ml beaker or a big trough and fill half of it with water. Cut a small piece of sodium (which is kept in kerosene) and put the sodium piece in water using forceps. This piece of sodium floats on the surface of water with a hissing sound.

This shows that sodium is reacting extremely fast with water.
Repeat the same experiment using aluminium, and iron. We will not see any change even after five minutes. This is because these metals react extremely slow with water. This shows metals react with water at different rates.

Activity – 7

Question 7.
Reaction with Acids.
Fill the reactions of the following metals and non-metals with dilute hydrochloric acid and dilute sulphuric acid.
Iron, Zinc, Copper, Sulphur, Aluminium, Graphite, Magnesium and Iodine.

Observation:
We find that some metals react with dilute HCl or H₂SO₄ liberating hydrogen but non-metals usually do not react with acids.

Activity – 8

Question 8.
Reactivity of metals:
Take six beakers and label them a, b, c, d, e and f. Take 50 ml of water in each beaker and dissolve a spatulaful of copper sulphate in beakers ‘a’ and ‘b’. Dissolve a spatulaful of zinc sulphate, in beakers ‘c’ and ‘d’. Iron sulphate in beakers ‘e’ and ‘f’.

• Zinc granules in beaker ‘a and e’
• Iron nail in beaker ‘b and d’
• Copper turnings in beaker ‘c and f’

Leave the beakers undisturbed. Record the changes in the colour of the solution in the table.

Solutions	Observations
Beaker a	The blue colour of copper sulphate disappears and a powdery red mass of copper is deposited at the bottom of the beaker ’a’.
Beaker b	In beaker ’b’ red copper is found at the bottom of the beaker and on the nail leaving light green iron sulphate solution.
Beaker c	No change
Beaker d	No change
Beaker e	No change
Beaker f	No change

a) What could be the reasons behind these changes?
Answer:
In beaker ‘a’, zinc displaces copper from copper sulphate giving rise to colourless zinc sulphate. Iron displaces copper from copper sulphate in beaker ’b’ leaving light green colour of iron sulphate and zinc displaces iron from Iron sulphate by change the colour from light green to colour less:
Copper sulphate + Zinc → Zinc sulphate + Copper
Copper sulphate + Iron → Iron sulphate + Copper
Iron sulphate + Zinc → Zinc sulphate + Iron

b) Do you find any changes in beakers c, d and f?
Answer:
There is no change in beakers c, d and f. The reason is

1. Copper is unable to displace zinc from zinc sulphate in beaker ‘c’.
2. Copper is unable to displace iron from iron sulphate in beaker ‘f’.
3. Iron is unable to displace zinc from zinc sulphate in beaker ‘d’.

c) Why does iron is unable to displace zinc from zinc sulphate?
Answer:
Iron is less reactive than zinc. A more reactive metal can replace a less reactive metal from its salt solution. But a less reactive metal unable to displace a more reactive metal from its salt solution.
The order of reactivity of given metals are Zinc > Iron > Copper

AP State Syllabus AP Board 8th Class Physical Science Solutions Chapter 3 Matter Around Us Textbook Questions and Answers.

AP State Syllabus 8th Class Physical Science Solutions 3rd Lesson Matter Around Us

8th Class Physical Science 3rd Lesson Matter Around Us Textbook Questions and Answers

Improve Your Learning

Question 1.
Describe an activity which provides the evidence for
a) the motion of particles
b) attraction between particles
c) inter-particle space
Answer:
a) An activity which provides the evidence for the motion of particles:
Materials required: Two 250 ml round bottom flasks, red or blue ink, dropper, Potassium permanganate (KMnO₄) solution.
Procedure:

1. Take two 250 ml round bottomed flasks and fill them with water.
2. Use a dropper and put a few drops of blue or red ink slowly along the sides of first flask.
   
3. Use a dropper and put one or two drops of KMnO₄ solution along the sides of second flask.
4. We observe that in the first flask the ink drops slowly diffusing and mix with water, so as to change the colour of water to red/blue.
5. In the second flask we observe that the KMnO₄ solution diffuses fast in the water and the colour of water changes.
6. This activity provides an evidence for the motion of particles.

b) An activity which provides the evidence for the attraction between particles:

1. Open a water tap and allow the water to reach the ground.
2. Now try to break the stream of water with your finger.
3. We can break the stream momentarily, but not permanently.
4. The reason behind the stream of water remaining together is the force of attraction between the water particles.
5. Now try to break a piece of iron nail with your hands.
6. We cannot break it, because the force of attraction between the particles of nail is very high.
7. Do the same with a piece of chalk. We can break it easily, due to the weak attraction forces among the particles of piece of chalk.
8. From the above, we can say that the particles of matter have attractive forces among them to keep the particles together.
9. These forces of attraction are not equally strong in all the forms of matter.

c) An activity which provides the evidence for the inter-particle space:
Materials required: Beaker, water, salt, spoon and a glass rod.
Procedure:

1. Take a graduated beaker and fill it with some water and mark the level of water.
2. Add some salt and stir it thoroughly with a glass rod.
3. Observe the change in water level. There will be no change in it.
   
4. Add some more salt and stir it again.
5. Observe the change in water level. There will be no change.
6. Continue this process till you see some salt remains undissolved in water.
7. From this activity, we can say that solid and liquid particles have some space between them.
8. The solid particles enter into the space between the liquid particles on dissolving solid in liquid.
9. This process continues till all the space in liquid particles is occupied by solid particles.
10. After completion of this occupation, the solid particles, as there is no space to occupy remain undissolved.

Question 2.
Name the characteristics of matter that are demonstrated by diffusion.
Answer:
The characteristics of matter that are demonstrated by diffusion:

1. Matter is made up of tiny particles.
2. Particles of matter have space between them.
3. Particles of solids and liquids diffuse into liquids.
4. Particles of gases diffuse into gases.
5. Rate of diffusion of gases is higher than that of liquids or solids.
6. Particles of solids occupy the space between the particles of liquids on addition of a solid to a liquid.
7. Particles of matter move continuously in liquids and gases.

Question 3.
“When sugar is dissolved in water, there is no increase in volume.” Is it true or false? Comment on the statement keeping in mind the amount of sugar, amount of water, etc.
Answer:
This statement is true.
Reason: When sugar is dissolved in water, the particles of sugar occupy the space between the particles of water. Hence there is no change in the volume of water.
Conditions for observing the change in volume of water:
If we go on adding sugar without increasing the quantity of water, there will be no space between water particles, to be occupied by sugar particles. Hence the sugar remains undissolved.

Question 4.
Is there any change in mass when a substance changes its state? Explain with example.
Answer:

1. Take a beaker and fill it with ice cubes.
2. Find the mass (m₁) of the beaker along with ice cubes using a spring balance.
3. Keep the beaker at rest for some time, till the ice changes into water.
4. Then find the mass (m₂) of the beaker along with water.
5. We observe that m₁ = m₂.
6. We conclude that the mass never changes when a substance changes its state.

Question 5.
Do all substances change from solid to liquid and liquid to gas on heating ? Explain. Ans. All substances cannot change from solid to liquid and liquid to gas on heating.
e.g.:

1. When wood is heated, it cannot change its state from solid to liquid, but the form of substance changes.
2. Mercury/blood.

Question 6.
Define the following terms:
a) Melting point
b) Boiling point
c) Evaporation
Answer:
a) Melting point: The temperature at which a solid melts to become a liquid is called “melting point”.
b) Boiling point: The temperature at which a liquid starts boiling at the atmospheric pressure is known as its “boiling point”.
c) Evaporation : The phenomena of change of a liquid into vapours at any temperature below its boiling point is called “evaporation”.

Question 7.
Correct the following statements.
a) Water boils at 100°C under atmospheric pressure.
Answer:
This is a correct statement.

b) A liquid evaporates above its boiling point.
Answer:
This statement is incorrect.
Reason: Evaporation takes place at any temperature below its boiling point.

c) Solids have the largest inter-particle space.
Answer:
This statement is incorrect.
Correct Statement: The inter-particle space of solids is minimum.
Explanation: The force of attraction between the particles is also very high due to less inter-particle space. Hence solids have definite shape and a fixed volume.

d) Gases have the strongest inter-particle forces.
Answer:
This statement is incorrect.
Correct Statement: Gases have weakest inter-particle forces.
Explanation: The inter-particle space for a gas is maximum. Hence the inter-particle forces are also weak. Due to this gases have no definite shape or fixed volume. They have to be stored in a closed container always.

Question 8.
Why do we prefer to sip hot tea with a saucer rather than a cup ?
Answer:

1. The surface area of saucer is more than the surface area of a cup.
2. We know that the rate of evaporation increases with an increase of surface area.
3. The hot tea particles can easily escape from the saucer than a cup.
4. Hence hot tea becomes cold easily in a saucer than a cup.
5. So we prefer to sip hot tea with a saucer rather than a cup.

Question 9.
When water solidifies to ice then heat is
a) Liberated
b) Absorbed
c) No change
d) Depending upon the condition heat may absorbed or liberated.
Answer:
a) Liberated

Question 10.
Convert the following temperatures to the Celsius scale.
a) 283 K   b) 570 K
Answer:
a) We know that 273 K = 0°C
283 K = 283 – 273 = 10°C
∴ 283 K = 10°C

b) We know that 273 K = 0°C
570 K = 570 – 273 = 297
∴ 570 K = 297°C

Question 11.
Convert the following temperatures to the Kelvin scale,
a) 27°C   b) 367°C
Answer:
a) 27°C = 27 + 273 = 300 K
b) 367°C = 367 + 273 = 640 K

Question 12.
Fill in the blanks.
a) Matter changes from one state to another either raising the …………… or lowering the ……………..
b) A change in which a solid on heating directly changes into vapour state is called …………….
Answer:
a) temperature, temperature
b) sublimation

Question 13.
Match the following.
a) Conversion of liquid into gas      ( )        (i) gas
b) Non – compressible                    ( )        (ii) solid
c) Maximum expansion                   ( )        (iii) particle
d) Constituents of matter                ( )        (iv) evaporation
Answer:
a) iv
b) ii
c) i
d) iii

Question 14.
How can we smell perfume sitting several meters away from the source?
Answer:

1. We know that the particles of gas are highly mobile in the air.
2. The particles of perfume vapours also move in air for several meters.
3. Hence we can smell perfume, sitting several meters away from the source.

Question 15.
Steam produces more severe burns than boiling water. Think why?
Answer:

1. Steam particles have more energy than the particles of boiling water.
2. This is because particles in water vapour have absorbed additional energy in the form of latent heat of vaporization.
3. So, steam produces more severe burns than boiling water.

Question 16.
Make a model to explain the structure of particles in solids, liquids and gases.
Answer:
Students have to prepare their own models.

Question 17.
How do you appreciate sweating mechanism of human body to control the temperature of the body?
Answer:

1. When we do some physical exercise or hard work, sweating is observed on the body.
2. The sweat evaporates from the surface of our body by absorbing the heat from your body.
3. Thus the particles of liquid absorb energy from our body and escapes to the surroundings.
4. Due to this we feel cool.

Different shaped containers, Beaker, Measuring jar, Conical flask, Round bottomed flask, Test tubes, CNG related Pictures, 50 ml syringe, Incense stick, Scent bottle, Potassium permanganate, Copper sulphate, Long glass tube with scale, Liquid Ammonia, Hydrochloric acid, Cotton, Two rubber corks, Two tongs, Dropper, Water, Salt, Thermometer, Spirit lamp, China dish.

8th Class Physical Science 3rd Lesson Matter Around Us InText Questions and Answers

8th Class Physical Science Textbook Page No. 31

Question 1.
Is there any substance which can be found in three states like water?
Answer:
Yes. The substance which can be found in three states like water is wax.

Question 2.
What are the properties that lead us to consider petrol or milk as liquids?
Answer:
Petrol and milk are considered as liquids because they have no fixed shape. But they get the shape of the container in which they have been poured.

Question 3.
Do solids have definite shape and fixed volume?
Answer:
Yes, solids have definite shape and fixed volume.

8th Class Physical Science Textbook Page No. 32

Question 4.
What is the shape of the water in different containers?
Answer:
Water gets the shape of containers in which it has been poured.

Question 5.
Is it same in all cases or different?
Answer:
Yes, it is same in all cases.

Question 6.
What shape does water take if it spills on the floor?
Answer:
Water spreads on floor if it spills on the floor.

Question 7.
Are the levels of water and milk same?
Answer:
Yes, the levels of water and milk are same.

Question 8.
Can you guess the volume of oil?
Answer:
Volume of the oil is equal to 50 ml.

Question 9.
What does a fluid mean?
Answer:
Fluid is a substance which can flow easily.

8th Class Physical Science Textbook Page No. 33

Question 10.
Does CNG have a fixed volume?
Answer:
No, CNG does not have a fixed volume.

Question 11.
Does CNG have a definite shape?
Answer:
No, CNG doesn’t have a fixed shape. Its shape is depending on the containers.

8th Class Physical Science Textbook Page No. 34

Question 12.
Does the smell from burning incense stick and deodorant spray reach someone on the other end at the same time?
Answer:
The smell from deodorant spray reaches someone on the other end faster than the smell from incense stick.

8th Class Physical Science Textbook Page No. 36

Question 13.
Why do gases diffuse faster than solids and liquids?
Answer:
The molecules in the gas are far from each other i.e., the inter molecular space is very high than in solids and liquids. Hence they have less attractive power. So, gases diffuse faster than solids and liquids.

Question 14.
When does water change into ice and then into vapour?
Answer:
Water when cooled in a refrigerator, it becomes ice. (Decreasing the temperature).

8th Class Physical Science Textbook Page No. 39

Question 15.
What type of changes occur inside the matter during a change of state?
Answer:
Inside the matter, we observe the increase/decrease in volume during the change of state.

Question 16.
How does this change of state take place?
Answer:
Change of state takes place by change in temperature.

Question 17.
What does happen to the particles of matter during a change of state?
Answer:
During a change of state, the kinetic energy of particles may increase/decrease, resulting in the increase/decrease of inter molecular attraction.

8th Class Physical Science Textbook Page No. 41

Question 18.
What will does happe when we apply pressure and compress a gas enclosed in a cylinder?
Answer:
When pressure is applied and compressed the volume of a gas in a cylinder decreases. (According to Boyle’s law).

Question 19.
Will the particles come closer?
Answer:
Yes, the inter molecular space between the particles decreases and they come close.

Question 20.
Do you think that increasing or decreasing the pressure can change the state of matter?
Answer:
Change in pressure can change the state of matter.

Question 21.
Can we liquify gases by applying pressure or reducing temperature?
Answer:
Gases can be liquefied by cooling below its critical temperature. Hence, change in temperature and pressure causes the gases to liquefy.

Question 22.
Do we always need to supply heat or change the pressure for changing the state of matter?
Answer:
It is required. But in some cases like natural evaporation of water, it is not necessary.

Question 23.
Can the change of state from liquid to vapour take place without the liquid reaching its boiling point?
Answer:
Yes, it is possible in case of drying the wet clothes. In the process, water direly changes into vapour form without reaching its boiling point.

Question 24.
Can you give few more examples for evaporation?
Answer:
Evaporation of iodine, drying up of wet body, etc.

Question 25.
What could be the reasons for this type of changes in states?
Answer:
In liquid s, the particles at the surface possess higher energy than particles in the bulk of watt.. The particles on the surface are able to break away from the force of attraction of other particles and change into vapour state.

Think & Discuss

8th Class Physical Science Textbook Page No. 34

Question 1.
Rubber band Activity:
a) Let us stretch a rubber band. Is there a change in its shape?
b) Is rubber band solid or liquid? Why?
Answer:
a) When rubber band is stretched it changes its shape.
b) It is a solid. If stretching is stopped, the rubber band regains its shape. If the stretching is too much, the rubber band permanently loses its shape.
Reason : Rubber band is a solid, but the nature of particles by which the rubber band is made is responsible for the above phenomena.

Question 2.
Powdered salt Activity:
a) Which shape does the powdered salt take?
b) Can you say that salt is a liquid on the basis of change in its shape? Justify your answer. Take a sponge. Observe its shape.
Answer:
a) Powdered salt takes the shape of the container, b) It is a solid.
Justification:

1. Change in shape or state means a complete change in the arrangement of particles.
2. Powdered salt is a composition of tiny particles, which do not change their shape.

Question 3.
Sponge Activity:
Can you compress it? Is it a soild? Why? Think. Is anything coming out from the sponge when it is compressed.
Answer:

1. Sponge can be compressed.
2. It is a solid.

Justification :

1. The inter-particle space is slightly more than a rigid body.
2. So that it can be compressed.

Question 4.
Why can’t you able compress a wooden block ? (or) Why aren’t you able to compress a wooden block ?
Answer:

1. The inter-particle space is very less in a wooden block.
2. So we cannot compress it at ordinary conditions.

8th Class Physical Science Textbook Page No. 42

Question 5.
Why do we wear cotton clothes in summer?
Answer:

1. More sweat is produced from our body during summer due to excess of external temperature.
2. We feel cool when the sweat is evaporated.
3. On wearing cotton clothes, the clothes absorb sweat from our body. So, we feel cool.
4. Other clothes like silk, polyester, etc. cannot absorb sweat.
5. Hence we wear cotton clothes in summer.

Question 6.
Why do we see water droplets on outer surface of a glass containing ice-cold water?
Answer:

1. Ice-cold water in the glass cools its surface.
2. Air around the glass contains water vapour which is warmer than the surface of the glass.
3. Due to the cold glass, air close to its surface will also become cooler.
4. This changes the water vapour in the air around the surface of the glass into water.
5. This water forms small drops on the outer surface of the glass.

Question 7.
Why do pigs toil in the mud during hot summer?
Answer:

1. Generally, the temperature of body is controlled through the sweating evaporation.
2. In the case of pigs, these have less sweat pores on their skin surfaces. So sweating evaporation process does not take place.
3. Because of this type of arrangement in pigs, they toil in the mud ponds more time during hot summer.

8th Class Physical Science 3rd Lesson Matter Around Us Activities

Activity – 1

Identifying the shape and volume of liquids
Question 1.
(a) Prove that the liquids have no fixed shape.
Answer:

1. Collect transparent containers of different shapes.
2. Take some water using the measuring jar.
3. Pour the water in one of the containers.
4. Observe the shape of water.
5. Pour the same water in different containers and observe the shape of water.
6. We observe that the water (liquid) takes the shape of container.
7. We can say that liquids have no fixed shape.
   

(b) Prove that the liquids have fixed volume.
Answer:

1. Take 50 ml of water with a measuring jar.
2. Pour this water in a transparent beaker.
3. Mark the level of water on the beaker and throw the water out.
4. Now measure 50 ml of milk, and pour it in the same beaker.
5. Mark the level of milk on it, and remove milk from the beaker.
6. Now take 50 ml of oil and pour it in the same beaker.
7. Mark the level of oil on it, and remove the oil from the beaker.
8. We observe that the mark on the beaker is same for water, milk and oil.
9. This proves that the liquids have a fixed volume.

Activity – 2

Question 2.
Do the gases have a definite shape and a fixed volume?
Answer:
CNG (Compressed Natural Gas) is stored in a tank. In vehicles CNG is stored in cylinders. We observe that CNG and all other gases neither have a fixed shape nor fixed volume.

Activity – 3

Observing the compressibility of different materials
Question 3.
Prove that the gases are highly compressible than liquids and solids.
Answer:

1. Take a 50 ml syringe.
2. Draw the piston to suck in air.
   
3. Place your finger on the nozzle and press.
4. Observe depth of piston moved into syringe and note the height of air column.
5. We feel hard to press the piston after certain height.
6. Here the air in the syringe is compressed.
7. Now fill water in the syringe and do the same experiment.
8. Note the height of water column when you feel hard to press the piston.
9. Here the height of water column is more than the height of air column.
10. Now take a piece of wood or iron and press it with your thumb.
11. We cannot find any observable change in its volume.
12. From the above observations, we can say that gases are highly compressible than liquids and solids.

Activity – 4

Observing the diffusion of gases
Question 4.
Describe an activity to observe the diffusion of gases.
Answer:

1. Ask your friend to hold an unlit incense stick and stand in one corner of the room.
2. Then you go and stand in the other corner.
3. We cannot observe any smell (This depends on the type of incense stick).
4. Now ask your friend to light the incense stick.
5. After a few seconds, we can observe the smell of incense stick.
6. The scent in the vapour form and smoke mixes with air and moves across the room and reaches our nose.
7. This activity proves that the gases can diffuse.

Activity – 5

Observing the diffusion of liquids
Question 5.
Write an activity which shows the diffusion of liquids.
Answer:
Take 250 ml round bottomed flask with 2/3rd water in it. Use a dropper and put a few drops of blue or red ink or Potassium permanganate (KMnO₄) solution slowly along the sides of the flask.

We can observe that liquids also diffuse into each other like gases.

Activity – 6

Observing the diffusion of particles of solids into liquids
Question 6.
Prove that the particles of solids diffuse into liquids.
Answer:

1. Take a beaker full of water.
2. Add a few crystals of potassium permanganate to it.
3. We observe that the diffusion of potassium permanganate crystal into water and the colour of water changes.
4. Repeat the experiment with crystals of copper sulphate.
5. Here also we observe the diffusion of CuSO₄ crystals into water and the colour of water changes.
6. From the above observations, we found that the particles of solids diffuse into liquids.

Lab Activity Diffusion of two gases
Question 7.
Describe an experiment to measure the speed of diffusion of two gases.
Answer:
Aim: To observe the speed of diffusion of two gases.
Materials required : Long glass tube with scale, liquid ammonia, Hydrochloric acid (HC/), pieces of cotton, two rubber corks and two tongs.

Procedure:

1. Take a one meter long narrow glass tube.
2. Take two pieces of cotton wool.
3. Soak one piece of cotton wool in HCl solution.
4. Soak another piece of cotton wool in NH₃ solution.
5. Insert them separately at the two ends of the tube with the help of tongs.
6. Close the ends of the glass tube with rubber cork and observe.
7. The HCl gives off hydrogen chloride gas and ammonia solution gives off ammonia gas.

Observation:

1. Both gases react together to form a white ring in the tube due to formation of ammonium chloride.
2. Measure the distance of white ring from two ends of the glass tube.

Explanation:
We can observe that the ammonia gas travelled faster. So that the distance of white ring is more from ammonia end than hydrochloric acid end.

Activity – 7

Question 8.
How small are the particles of matter?
Answer:

1. Take a beaker with water. Mark the level of water.
2. Add 1 or 2 crystals of potassium permanganate and dissolve in water.
3. Colour of water changes to light violet.
4. Now take out approximately 10 ml of this solution and add it to 90 ml of clear water in another beaker.
5. Now the colour of water will be lighter than in the previous one.
6. Again take out 10 ml of this solution and add it to another 90 ml of clear water.
7. Carry out this process 4, 5 times and observe the changes in colour of the solution.
8. We observe the water in last beaker also changed to light violet.
9. From this activity we conclude that both solids and liquids are made up of tiny particles.

Activity – 8

There exists space between particles
Question 9.
Write an activity which shows the space between particles.
Answer:

Procedure: Take a graduated beaker and fill it with some water and mark the water level. Add some salt and stir it thoroughly with a glass rod. Observe if there is any change in water level. Add some more salt and stir it again.
Observations: From the activity we can conclude that both solid and liquid particles have some space between them. Hence the solid particles enter into the space between the liquid particles on dissolving solid in liquid. So there is no change in the water level.

Activity – 9

Observing the force of attraction between the particles of matter
Question 10.
Write an activity which provides an evidence for the force of attraction between the particles of the matter.
Answer:
Procedure:
Open a water tap and allow the water to reach the ground. Now try to break the stream of water with our finger. But we cannot break the stream permanently.
We cannot also break a piece of iron nail with our hands. But we can break a piece of chalk with our hands.
Observations: From the above observations we can say that particles of the matter have forces acting between them that keeps the particles together.
It is also clear that this force is not equally strong and different in different forms of matter.

Activity – 10

Effect of temperature on change of state
Question 11.
Write an activity to know the effect of temperature on change of state of matter.
Answer:

1. Take about 100 g of ice in a beaker.
2. Suspend a laboratory thermometer so that its bulb is in contact with the ice.
3. Set up the beaker as shown in the figure.
4. Note the temperature.
5. Now heat the beaker slowly.
   
6. Record the change in temperature after every 30 seconds.
7. Let the ice melt completely.
8. Now place a glass rod in the beaker and continue heating till water starts boiling.
9. After some time all the water will get vapourised.
10. From this we understand that substances around us change state from solid to liquid and from liquid v to gas on application of heat.
11. There are some substances which can change directly from solid state to gaseous state and vice versa without changing into the liquid state.

Activity – 11

Effect of surface area, humidity and wind speed on evaporation
Question 12.
(a) Explain the effect of surface area on the rate of evaporation.
Answer:
Rate of evaporation increases with an increase of surface area.
Explanation:

1. During evaporation process, the particles escape from the surface of liquid.
2. The increase in the surface area provides more scope for particles to escape from the surface.
3. Hence it leads to increase the rate of evaporation.

Ex: Water in a China dish evaporates faster than the water in test tube.

(b) Explain the effect of humidity on the rate of evaporation.
Answer:
Rate of evaporation decreases with the increase in humidity.
Explanation:

1. The amount of water present in air is called humidity.
2. The air around us cannot hold more than a definite amount of water vapour at a given temperature.
3. If the amount of water vapour is high in air, then the rate of evaporation decreases. Ex : Clothes dry slowly on a rainy day than on a normal day.

(c) Explain the effect of wind speed on rate of evaporation.
Answer:
Rate of evaporation increases with the increase in wind speed.
Explanation:

1. Because of increase in wind speed, particles of water vapour move away with the wind.
2. Due to this, amount of water vapour in the surroundings decreases.
3. It leads to increase in the rate of evaporation.
   Ex: Clothes dry faster on a windy day or under fan than a normal day.

AP State Syllabus AP Board 8th Class Biology Solutions Chapter 11 Why Do We Fall Ill Textbook Questions and Answers.

AP State Syllabus 8th Class Biology Solutions 11th Lesson Why Do We Fall Ill

8th Class Biology 11th Lesson Why Do We Fall Ill Textbook Questions and Answers

Improve Your Learning

Question 1.
A doctor/nurse/health-worker is exposed to more sick people than others in the community. Find out how she/he avoids getting sick herself/himself.
Answer:

1. By choosing nutritious food and an active lifestyle, managing stress, using tobacco- free, getting preventive immunizations and screenings and choosing protection measures.
2. Maintaining good hygiene:
   By washing hands frequently, cleaning their stethoscopes from patient to patient, using gloves.
3. Recognising the symptoms quicker and knowing what to do can help speedy recovery, easier access to medical care. (E.g.: They can self-prescribe, can ask col¬leagues for help etc.)

Question 2.
Differentiate the infective and non-infective diseases.
Answer:

1. Infectious diseases can be spread from person to person.
   Non-infectious diseases can not be spread from person to person.
2. Infectious diseases are caused by pathogens (microbes) which are disease causing organisms.
   The major group of pathogens (microbes) are viruses, bacteria, fungi, single cell organisms like protozoans, multicellular organisms like worms.
   Non-infectious diseases are not caused by Pathogens (microbes), but can be caused by physiological malfunctions, environmental or chemical factors, heredity, unknown causes. These are mostly internal, non-infectious causes.
3. Examples of infectious diseases are Viral, diseases, bacterial etc.
   Example for non infectious causes are some cancers caused by genetic abnormali¬ties and high blood pressure caused by excessive weight and lack of exercise.

Question 3.
Why acute disease become chronic disease?
Answer:

1. Some diseases last for only very short periods of time and these are called acute diseases.
   E.g.: Common Cold lasts only a few days.
2. Some other diseases or ailments can last for a long time, even as much as a life time and are called chronic diseases.
   E.g,: The infection causing elephantiasis, which is very common in some parts of India.
3. As an example, a cough and cold which all of us have from time to time. Most of us get better and become well within a week or so.
4. But if we get infected a chronic disease like tuberculosis of the lungs, it takes over the years to suffer with cough and lose weight and feel tired all the time.
5. In other words, we are likely to have prolonged general poor health if we have a chronic disease.
6. Chronic diseases therefore have very drastic, longterm effects on people’s health
   as compared to acute disease.
7. One reason might be that, because the person is not well nourished and does not get enough food and it is because of poverty, the acute disease becomes a chronic disease.

Question 4.
Draw the figure of leishmania and trypanosome.
Answer:

Question 5.
Ramu was effected with small pox. What advice do you give Ramu for not spreading disease?
Answer:
Prevention of Small Pox:

1. Isolation of the infected person.
2. Surrounding should be kept clean and hygeinic.
3. Clothes of the infected person must be washed in hot water and dried in the Sun.
4. They should not be used by others.
5. Small Pox can be prevented by taking vaccine against it.
6. But in 1776 Edward Jenner discovered a vaccine for small pox. Now it is wiped out from our country.

Question 6.
How do you appreciate for role of vaccine in preventing disease?
Answer:

1. Vaccination was discovered by a British doctor called Edward Jenner in the year 1776. Since then, this method has been modified and has become most popular for making people resistant to disease.
2. In this process, the disease causing organism are cultured in the laboratory and are collected. They are killed by heat treatment.
3. The dead micro-organisms are made into a suspension and injected into humans. The body reacts to these dead micro-organisms as if they are alive and are produces antibodies.
4. Next time when the same disease producing micro-organisms enter the body, these antibodies will react and kill them.
5. Thus the person is not affected by the disease, even if he is exposed to the disease causing microorganisms. Vaccination also prevents the spread of epidemics.
6. At present, vaccines are available for various diseases-Cholera, typhoid, diphtheria, whooping cough, polio, tuberculosis etc. Some of the vaccines if taken once, the immunity persists for life time, while in some cases the immunity will lasts only for limited amount of time.

Question 7.
Prepare a questionnaire to collect the information from your local health worker about spreading of diseases?
Answer:

1. What are the causes for a disease?
2. Name the organisms that cause diseases.
3. Name the diseases caused by virus, bacteria, fungi and protozoans.
4. How the infectious agents spread?
5. Name the diseases caused by air, water and physical contact.
6. What are the symptoms of Typhoid and Jaundice?
7. How can we prevent exposure to infectious diseases?
8. How do we kill microbes?
9. How to get rid of an infection in some one who has the disease?
10. What are the treatments for any type of diseases?
11. What are the measures taken by Public Health,Programmes to prevent diseases?
12. What is immunization? What are antibiotics?
13. What is the duty of everyone in the community for the effective prevention of infectious diseases?

Question 8.
How many times did you fall ill in the last one year? What were the illnesses?
a) Think of one change you could make in your habits in order to avoid any of/ most of the above illnesses.
b) Think of one change you would wish for in your surroundings in order to avoid any of/most of the above illnesses.
Answer:
In the last one year, fall ill for one time with Malaria.
Symptoms:

1. It is a communicable disease caused by the Protozoan Plasmodium Falciparum. It is spread by the infected female anopheles mosquito.
2. It starts with extreme cold. Patient wants to be covered with heavy blankets. This is followed by fever, as high as 106° F.
3. There will be severe head ache and body pains. There will be sweating.
4. In children the parasite enter and block the capillaries, supplying blood to the brain. The blood vessels may ruptures child becomes unconscious and may even die.

a) Think of one change you could make in your habits in order to avoid any of/ most of the above illnesses.
Answer:
Preventive measures of malaria:

1. To reduce the mosquito population successfully.
2. By protecting ourselves from mosquito bites, the spread of malaria can also be prevented.
3. Best method is to use mosquito nets while sleeping and by using mosquito proof nets for windows and doors. These nets do not allow mosquitoes to enter the house.

b) Think of one change you would wish for in your surroundings in order to avoid any of/most of the above illnesses.
Answer:

1. Preventing water stagnation in water tanks, drainage canals, and discarded vessels lying outside. The stored water tanks should be emptied frequently and filled with fresh water.
2. Spraying of insecticides or light oil such as kerosene on stagnant water, especially in drainage water.
3. Growing of specific varieties of fishes in stagnant water. They feed on mosquito larvae.

Question 9.
Conduct a survey in your neighbourhood to find out what the three most common diseases are. Suggest three steps that could be taken by your local authorities to bring down the incidence of these diseases.
Answer:
The most common cause for the spread of diseases in our neighbourhood is by drinking of contaminated water. Polio, Cholera, Typhoid, Jaundice and Amoebiasis and several worms spread through drinking water.
Preventive Measures:

1. Drinking water is purified by filtration and chlorination before it is supplied through municipal taps and provide safe drinking water.
2. Providing basic sanitation by keeping the surroundings clean.
3. Arranging the public health programmes to prevent and control of local diseases by giving immunisation to childhood.

8th Class Biology 11th Lesson Why Do We Fall Ill InText Questions and Answers

Question 1.
Let us read the wall writings on the panchayat office

Drink boiled water only.
Use mosquito nets.
Keep your surroundings neat and clean.
Do not left water to stagnate.
Eat food when it is hot.
Wash hands before eating food.
Wash hands after toilet.
Use toilets only, not defecate in open.
Keep lids on food vessels.
Wash vegatables before cooking

a) Why local Panchayats display such instructions on the wall?
Answer:
To bring awareness in the local people against diseases.

b) What do we come to know from such instructions?
Answer:
Such infections will spoil the health of people.

c) What would happen if we do not follow the instructions.
Answer:
People who would not follow the instruction may fall sick.

d) In which season do we generally find more mosquitoes? How do they affect us?
Answer:
Generally we find more mosquitoes in rainy season. Mosquitoes cause malaria.

e) What is health ? And when do we fall sick?
Answer:
Health is a state of being well enough to function physically, mentally and socially with optimum efficiency.
When disease causing organisms attack us we fall sick.

Question 2.
State any two conditions essential for good health.
Answer:
Clean surroundings and fresh air.

Question 3.
State any two conditions essential for being free of disease.
Answer:
Safety food and water and exercise to the body.

Question 4.
Are the answers to the above questions necessarily the same or different? Why?
Answer:
Different.

Question 5.
Do all diseases spread to people coming in contact with a sick person?
Answer:
No, some diseases are infectious and some diseases are non-infectious.

Question 6.
What are the diseases that are not spreading?
Answer:
Non-infectious diseases E.g.: Some cancers, high blood pressure etc.

Question 7.
How would a person develop those diseases that do not spread by contact with a sick person?
Answer:
Non-infectious diseases are some times caused by genetic abnormalities, excessive weight or lack of exercise.

Question 8.
List any three reasons why you would think that you are sick and ought to see a doctor. If only one of these symptoms were present, would you still go to the doctor? Why or why not?
Answer:
Because of not feeling well, unable to do daily work and when feeling uneasy thinking that we are sick we want to see the doctor. If the situation is unbearable then we would like to see the doctor.

Question 9.
In which of the following case do you think the long-term effects on your health are likely to be most unpleasant?
Answer:

1. If in the case of Jaundice, the suffering will be more and it will be cured only by taking medicines. Prescribed by a doctor.
2. Because this is the disease for liver, the normal functioning of the liver will be stopped, and feels unpleasant.

8th Class Biology 11th Lesson Why Do We Fall Ill Activities

Activity – 1

Question 1.
a) Find out what provisions are made by your local authority (Panchayat/ Municipal Corporation) for the supply of clean drinking water.
Answer:
The Panchayat/Municipal Corporation should filter the water and chlorinated before sending through pipes.

b) Are all the people in your locality able to access this?
Answer:
Yes, all the people can access this. The people are avail of this.

Activity – 2

Question 2.
a) Find out how your local authority manages the solid waste generated in your neighbourhood.
Answer:
The solid waste generated in the neighbourhood is collected and disposed.

b) Are these measures adequate?
Answer:
Yes. But still more they can take measures.

c) If not what improvement would you suggest?
Answer:
The authority can announce the public to reduce the waste in the household.
Suitable arrangements will be arranged for the garbage disposal, to prevent accumulation of waste in and around residential areas. This attracts the houseflies and other microbes to spread diseases.

d) What could your family do to reduce the amount of solid waste generated during a day/week from your house?
Answer:
The peels of fruits and vegetables and other waste materials which decay and turns good manure can deposit in the compost pit.

Activity – 3

Question 3.
Survey your neighbourhood to find out:
a) How many people did suffer from acute diseases during the last three months?
Answer:
More people suffered from acute diseases.

b) How many people did develop chronic diseases during this same period?
Answer:
Very few people develop chronic diseases.

c) And finally, what is the total number of people suffering from chronic diseases in your neighbourhood?
Answer:
One or two.

d) Are these answers to questions (I) and (2) different?
Answer:
Same.

e) Are these answers to questions (2) and (3) different?
Answer:
Same.

f) What do you think could be the reason for these differences? What do you think would be the effect of these differences on the general health of the population?
Answer:
In general people get acute diseases seasonally but chronic diseases are drastic, long term effect because of their poor health.

Activity – 4

Question 4.
a) Find out how many of in your class had cold/cough/fever recently.
Answer:
One or two or few students.

b) How long did the illness last?
Answer:
The illness lasts for one week.

c) How many of you took antibiotics?
Answer:
Half of the students took antibiotics.

d) How long did they suffer who took antibiotics pills?
Answer:
Seven days.

e) How long did they suffer who did not take antibiotics pills?
Answer:
Seven days.

f) Is there any difference between these two groups?
Answer:
No difference is seen between these two groups.

g) If yes, why ? If not, why not?
Answer:
Because antibiotics do not work against viral infections.

Activity – 5

Question 5.
Conduct a survey in your locality. Talk to ten families who are well-off and ten who are very poor. Both sets of families should have children who are below five years of age. Measure the heights of these children. Draw a graph of the height of each child against its age for both sets of families.
Families who are well – off

Name of the child	Age	Heights
1) C. Vivek	5	105 cm
2) B. Ramu	4	99 cm
3) B. Gopi	4	100 cm
4) R. Rahul	3	91 cm
5) B. Somu	2	86 cm

Families of very poor

Name of the child	Age	Heights
1) A. Kotaiah	5	100 cm
2) P. Ankalu	4	94 cm
3) B. Srinu	4	92 cm
4) C. Samuel	3	86 cm
5) P. Gopi	2	80 cm

a) Is there any difference between the groups? If yes, Why?
Answer:
Yes, there is a difference between the groups. The children who are sufficient nourishment have good health. Their growth is healthy.

b) If there is no difference, do you think that your findings mean that being well-off or poor does not matter tor health?
Answer:
The functioning of the immune system, like any other system in the body, will not be good if proper and sufficient nourishment and food is not available.
So the availability of proper and sufficient food helps us to be healthy.

Activity – 6

Question 6.
Rabies virus is spread by the bite of infected dogs and other animals. There are anti-rabies vaccines for both humans and animals.
a) Find out the plan of your local authority for the control of rabies in your neighbourhood.
Answer:
Control of Rabies:

1. Parental rabies vaccination of owned dogs.
2. Sterlization of pet dogs.
3. Unwanted dogs should not be abondoned.
4. Animal birth control attempt should be made to sterilize the stray dog population or other methods of birth control should be investigated.
5. Suitable infrastructure for garbage disposal, to prevent the accumulation of waste in and around residential areas.

This attracts stray and ownerless dog packs to these areas.
Vaccination:
Sufficient and affordable cell culture vaccine should be available for post exposure treatment.
Mass oral vaccination of the stray dog population.

b) Why we are normally advised to take bland and nourishing food when we are sick?
Answer:
When we fall sick our normal body functions will be affected the digestion will be slow, so it is advised to take bland and nourishing food when we are sick.

c) What are the different means by which infectious diseases are spread?
Answer:
The infectious diseases are spread through contaminated air, water, food and vectors like mosquitoes, flies, cockroaches, snails and even lice.

d) What precautions can you take in your school to reduce the incidence of infec-tious diseases?
Answer:

1. Encouraging sick students and staff to stay at home and seek medical attention for several illnesses.
2. Facilitating hand hygiene by supplying soap and paper towels and teaching good hand hygiene practicles.
3. Cleaning of class room materials and surfaces.
4. Daily announcements about preventing infectious diseases.
5. Encouraging students and staff to get annual influenza vaccination.

e) What is immunization?
Answer:
The creation of immunity against a particular disease, by vaccination of an organism for the purpose of making it immune to a particular pathogen (disease causing organ¬ism) is called immunisation.

f) What are the immunization programmes available at the nearest health centre in your locality?
Answer:
More children are being protected against vaccine preventable diseases, such as tuberculosis tetanus, pertusis (Whooping cough), diphtheria, polio, measles and now hepatitis – A, B then ever before.
The public health programme of childhood immunisation for preventing infectious diseases.

g) Which of these diseases are the major health problems in your area?
Answer:
Measles and jaundice.

AP State Syllabus 8th Class Maths Solutions 14th Lesson Surface Areas and Volume (Cube-Cuboid) InText Questions

AP State Syllabus AP Board 8th Class Maths Solutions Chapter 14 Surface Areas and Volume (Cube-Cuboid) InText Questions and Answers.

8th Class Maths 14th Lesson Surface Areas and Volume (Cube-Cuboid) InText Questions and Answers

Do this

Question 1.
Find the total surface area of the following cuboid.      [Page No. 298]

Answer:
i) l = 4 cm, b = 4 cm, h = 10 cm.
The total surface area of a cuboid = 2 (lb + bh + lh)
= 2 (4 × 4 + 4 × 10 + 4 × 10) = 2(16 + 40 + 40)
= 2 × 96
= 192 Sq. cms.

ii) l = 6 cm, b = 4 cm, h = 2 cm.
The total surface area of a cuboid = 2 (lb + bh + lh)
= 2(6 × 4 + 4 × 2 + 6 × 2)
= 2 (24 + 8 + 12)
= 2 × 44
= 88 sq. cms.

Question 2.
Let us find the volume of a cuboid whose length, breadth and height are 6 cm, 4 cm and 5 cm respectively.      [Page No. 287]

Let place 1 cubic centimeter blocks along the length of the cuboid. How many blocks can we place along the length? 6 blocks, as the length of the cuboid is 6 cm.
How many blocks can we place along its breadth? 4 blocks, as the breadth of the cuboid is 4 cm. So there are 6 × 4 blocks can be placed in a layer.
How many layers of blocks can be placed in the cuboid? 5 layers, as the height of the cuboid is 5 cm. Each layer has 6 × 4 blocks. So, all the 5 layers will have 6 × 4 × 5 blocks i.e. length × breadth × height.
This discussion leads us to the formula for the volume of a cuboid.
Volume of a cuboid = length × breadth × height      [Page No. 305]
Answer:
The dimensions of a cuboid are 6 cm, 4 cm, 5 cm respectively.
∴ Volume (V) = lbh
= 6 × 4 × 5.
= 120 cm³

Question 3.
Arrange 64 unit cubes in as many ways as you can to form a cuboid. Find the surface area of each arrangement. Can solid cuboid of same volume have same surface area? [Page No. 306]
Answer:
No. of cuboids are formed using 64 unit cubes
64 = 1 × 64 ……. (1)
= 2 × 32 …….. (2)
= 4 × 16 …….. (3)
1) l = 64 cm, b = 1 cm, h = 1 cm.
The total surface area of a cuboid, A = 2 (lb + bh + lh)
= 2 (64 × 1 + 1 × 1 + 1 × 64)
= 2 (64 + 1 + 64)
= 2 × 129
= 258 Sq. cm.

2) l = 32 cm, b = 2 cm, h = 1 cm.
A = 2 (lb + bh + lh)
= 2 (32 × 2 + 2 × 1 + 32 × 1)
= 2 (64 + 2 + 32)
= 2 × 98 = 196 Sq. cm.

3) l = 16 cm, b = 4 cm, h = 1 cm.
A = 2 (lb + bh + lh)
= 2 (16 × 4 + 4 × 1 + 16 × 1)
= 2 (64 + 4 + 16)
= 2 × 84 = 168 Sq. cm.

No, the volume of a cuboid is not same as the surface area of a cuboid.

Try These

Question 1.
Find the surface area of cube ‘A’ and lateral surface area of cube ‘B’.      [Page No. 300]

Answer:
a = 10 cm.
The total surface area of a figure ‘A’ = 6a²
= 6 × (10)²
= 6 × 100 = 600 Sq. cm.
Lateral surface area of a figure ‘B’ – 4a²
= 4 × (8)² [∵ a = 8 cm.]
= 4 × 64 = 256 Sq. cm.

Question 2.
Two cubes each with side ‘b’ are joined to form a cuboid as shown in the given fig. What is the total surface area of this cuboid?      [Page No. 300]

Answer:

Total surface area of a cuboid = 2 (lb + bh + lh)
= 2 (2b × b + b × b + 2b × b)
= 2 (2b² + b² + 2b²)
= 2(5b²) = 10b² Sq. cm.

Question 3.
How will you arrange 12 cubes of equal lengths to form a cuboid of smallest surface area?      [Page No. 300]

Answer:
We can’t obtain the least total surface area by arranging 12 cubes by side by side.

∴ A = 2 (lb + bh + lh)
= 2 (12 × 1 + 1 × 1 + 12 × 1)
= 2 (12 + 1 + 12)
= 2 × 25 = 50 Sq. cm.
We can obtain the least total surface area by arranging 3 cubes by 4 cubes.
∴ A = 2 (lb + bh + lh)
= 2 (3 × 1 + 1 × 4 + 3 × 4) (∵ l = 3; b = 1; h = 4)
= 2 (3 + 4 + 12)
= 2 × 19
= 38 Sq. cm.

Question 4.
The surface area of a cube of 4 × 4 × 4 dimensions is painted. The cube is cut into 64 equal cubes. How many cubes have
(a) 1 face painted? (b) 2 faces painted? (c) 3 faces painted? (d) no face painted?       [Page No. 300]
Answer:
If the 4 × 4 × 4 cube is divided into 64 equal cubes then the length of its each side = 1 unit.

[∵ \(\frac{4 \times 4 \times 4}{64}\) = 1]
a) No.of cubes (a = 4) have painted 1 face = 6(a – 2)² = 6(4 – 2)² = 6 × 4 = 24
b) No.of cubes have painted 2 faces = 12(a – 2) = 12(4 – 2) = 24
c) No.of cubes have painted 3 faces = 4 × a = 4 × 2 = 8
d) No.of cubes have painted no faces = (a – 2)³ = (4 – 2)³ = (2)³ = 8

Think, Discuss and Write

Question 1.
Can we say that the total surface area of cuboid = lateral surface area + 2 × area of base.      [Page No. 299]
Answer:
Total surface area of a cuboid = L.S.A + 2 × Area of base
= 2h (l + b) + 2 × lb
= 2lh + 2bh + 2lb
= 2 (lb + bh + lh)
We can conclude that total surface area of a cuboid = L.S.A + 2 × Area of base

Question 2.
If we change the position of cuboid from Fig. (i) to Fig. (ii) do the lateral surface areas become equal?     [Page No. 299]

Answer:
There will be no change in the L.S.A of a cuboid if its positions are changed.

Question 3.
Draw a figure of cuboid whose dimensions are l, b, h are equal. Derive the formula for LSA and TSA.       [Page No. 299]
Answer:

Lateral surface area of a cuboid
= 4 × (areas of 4 faces)
= 2 (l × h) + 2 × (b × h) (1 + 2 + 3 + 4 faces)
= 2h(l + b) sq.units (1 = 3, 4 = 2)
∴ Total surface area of a cuboid
= 4 × (Area of 4 faces) + (Areas of upper & lower faces)
= 2h (l + b) + 2 (lb)
= 2lh + 2bh + 27b
= 2 (lb + bh + lh) sq.units.

AP State Syllabus AP Board 8th Class Biology Solutions Chapter 6 Biodiversity and its Conservation Textbook Questions and Answers.

AP State Syllabus 8th Class Biology Solutions 6th Lesson Biodiversity and its Conservation

8th Class Biology 6th Lesson Biodiversity and its Conservation Textbook Questions and Answers

Improve Your Learning

Question 1.
Read this and answer the following questions.
Answer:
Biodiversity – 2050.
A news item on Biodiversity discussed by Conference of Parties (CoP) -2012- Hyderabad says in the next four decades the earth’s natural resources will be limited to grass lands, mountains, ice and arid and semi arid plains.
By 2050 the loss of Biodiversity will lead to unprecedented. Climate change would be the key factor. Nearly 1.3 million natural ecosystems will be without any original species.
(The coloured areas are indicators of biodiversity loss. The red areas show maximum biodiversity loss.)

a) What does the areas with colour codes indicate?
Answer:
The coloured areas are the indicators of Biodiversity loss.

b) Which areas show maximum biodiversity loss?
Answer:
The red areas show maximum biodiversity loss.

c) Which areas show minimum biodiversity loss?
Answer:
The blue areas show minimum biodiversity loss.

d) From 2010 – 2050 what difference do you find in the state of biodiversity?
Answer:
In the few decades earth’s natural areas will be limited to grass lands, mountains, ice and arid and semi arid plans. Nearly 1.3 million natural ecosystems will be without any original species.

e) So what steps would you suggest to conserve our biodiversity?
Answer:
Utilizing the forests resources judiciously without effecting the ecosystems. So that we can have a sustainable development in the forests and the biodiversity can be conserved for future generations.

Question 2.
How can you say that forests are biosphere reserves? Give reasons.
Answer:

1. Forests are the natural habitates for many types of plants (flora) and animals (fauna).
2. Plants are primary producers as they provide food for entire human population and all other living organisms on earth.
3. Every part of the plant is used by man and animals in their daily life, and also some of the exudates are used by man.
4. We get cereals, pulses, oil seeds, sugars, spices, drugs, timber, fibres and coir from plants.
5. In addition to this products like rubber, resins, fruits, vegetables, dyes, etc. are obtained from plants.
6. Variety of animals live in the forests. Major products obtained from animals are meat, milk hair and skin.
7. Primitive man obtained his food requirements primarily by hunting of animals in the forests.
8. The skin of animals like tiger, lion, leopard, deer, snakes and ivory from elephants are very valuable.
9. Thus we can say that forests are biosphere reserves.

Question 3.
What do you understand about the terms (a) extinct (b) endangered (c) endemic?
Give examples.
Answer:
a) Extinct: When animals vanish for ever from the earth it is said that the species has become extinct. E.g.: Sparrow, vulture.
b) Endangered : It is a warming signal about the organisms whose numbers have declined rapidly and the species might be wiped off from the earth in near future. Such organisms are called endangered species. E.g.: Lion, red fox, loris, wild cat, vulture.
c) Endemic: Plants or animal species found restricted to a particular area of a country are called endemic species. E.g.: Tiger, peacock, kangaroo, kiwi.

Question 4.
a) Extinct: When animals vanish for ever from the earth it is said that the species has become extinct. E.g.: Sparrow, vulture.
b) Endangered: It is a warming signal about the organisms whose numbers have declined rapidly and the species might be wiped off from the earth in near future. Such organisms are called endangered species. E.g.: Lion, red fox, loris, wild cat, vulture.
c) Endemic: Plants or animal species found restricted to a particular area of a country are called endemic species. E.g.: Tiger, peacock, kangaroo, kiwi.
Answer:

1. Some birds live in the same habitate throughout the year. Other birds which don’t have permanent nestlings join into small flocks and move from one region to the other for food and shelter called as ‘migration’ and such birds are called migratory birds.
2. Primary motivation for migration appears to be food. Also longer days of northern summer provide extended time per breeding birds to feed their young ones.

Question 5.
Identify the endemic and endangered species and write them below the pictures.
Answer:

Question 6.
What is the need of conducting biodiversity meet ? Collect information about these meetings when and where it was conducted and its agenda also.
Answer:
The need of conducting biodiversity meet is

1. Managing biodiversity in transboundary landscapes in Hindukush Mountains.
2. Conserving high altitudes wet lands of the Hindukush Himalayans.
3. Operationalizing nagoya protocall in South Asia.

AGENDA

1. Conservation of Biodiversity.
2. Sustainable use of components of Biological diversity.
3. Fair and equitable sharing of benefits arising out of the utilization of genetic resources.

33 Decisions were taken at cop – 11, Hyderabad among them some are given below.

1. Status of Nagoya protocol an axis to genetic resources and equitable sharing of benefits.
2. Review of progress in implementation of strategic plan for Biodiversity – 2011 – 20 and Aichi biodiversity targets.
3. Review of implementation of the strategy for resource mobilization including establishments of targets.
4. Financial mechanism.
5. Cooperation with other conventions International organization and initiatives.
6. Business and Biodiversity.
7. Engagement of other state holders major groups and sub – National authorities.
8. Progress report on gender main streaming
9. Periodicity of meetings.

Question 7.
Nowadays we find animals like leopards and bears intruding into our living places. What may be the reason for this?
Answer:

1. Forests are the living places for wild animals. Animals can get plenty of food, shelter from the shade of trees and they feel secure in the forests.
2. People are so greedy that they cut down the forest areas for logging of wood, to increase agriculture, and for human habitations.
3. They clear the forests to construct, thermal power stations, industries and many buildings which leads to destruction of forests.
4. Due to deforestation, nowadays the animals like leopard and bears, lost their food and shelter, to satisfy their hunger and to keep themselves alive, they intruding into our living places.
5. To escape from hunters and from climatic conditions because of deforestation, is may be one more reason, for the animals coming into our living places.

Question 8.
Make a list of animals/birds seen now and 30 years ago. Take the help of your elders. Write few reasons for their disappearance.
Answer:

1. List of Animals and Birds: Lion, Tiger, Jackel, Fox, Wolves, Deer, Monkeys, Hyena, Squirrel, jungle foul etc. Birds like Crow, Pigeon, Peacock, Koel, Parrot, Flemingo, Mynah, King Fisher, Emu, Migratory shore birds etc.
2. The endangered species of plants and animals of India are:
   Lion, Red fox, Single horned (Rhinoceros), Vulture, Spotted chital deer, Loris, Black spider monkey, wild cat, cycas, Rauvolfia serpentine, Nepenthes, Sandle wood tree.
3. These species include mammals – Indian cheetah, Japan Rhinoceros and Sumatran Rhinoceros. Some species of birds of gone extinct in recent times – including pink headed duck (Rhodonessa caryophyllacca) and Himalayan quail (Ophrysia superciliosia)
4. Warbler (Acrocephalus orinus) – Rampur in H.P was rediscovered after 139 years in Thailand.
5. Based on the case study we find that many animals that were found earlier are not found now.
6. The reason for this is exploitation of land and forest resources by humans, along with hunting and trapping for food and sport has led to the extinction. Feeding of Diclofenac treated cattle is the reason for disappearance of vulture.

Question 9.
Select an area in your locality. Observe the animals (living and visiting) for a day. Prepare a list and plot a graph.
Answer:
The animals in our locality:

1. Dog
2. Cat
3. Rat
4. Mouse
5. Bandicoots
6. Squirrels
7. Frogs
8. Lizards
9. Garden Lizard
10. Monkeys
11. Buffaloes
12. Goats
13. Donkeys
14. Mongoose
15. Snake
16. Sheep
17. Fish
18. Tortoise
19. Rabbit
20. Parrot
21. Crow
22. Hens
23. Koel
24. Pigeon
25. Butterflies
26. Houseflies
27. Dragonflies
28. Mosquitoes
29. Honey bee
30. Cockroach

Question 10.
When tree is considered as an ecosystem, record the flora and fauna connected with it.
Answer:
Flora and Fauna of a tree.
Flora:

1. Grass,
2. Trida (shrub),
3. Datura (Herbs),
4. Creppers,
5. Mosses,
6. Fungi.

Fauna: Squirrels, Butterflies, Dragonfly, Mosquitoes, Birds, Snakes, Ants, Catterpillers, Beetles, Buffaloes, Goats, Human beings, Mouse, Lizard.

Question 11.
Browse through the internet or books on wild life and gather information on birds sanctuaries in India. Prepare a list of birds migrating to India.
Answer:

Birds migration to India:

1. Siberian cranes
2. Greater flamingos
3. Ruff
4. Black winged stilt
5. Common teal
6. Common Green Shark
7. Northern Pintail
8. Yellow wag tail
9. White wag tail

Question 12.
Visit local forest office and collect the data of local flora and fauna.
Answer:
Horticultural Resources: Guava, Mango, Papaya, Sapota, Banana, Coconut, Citrus.
Major oil seeds: Groundnut, Sunflower, Oil palm.
Major food crops: Paddy, Jowar, Ragi, Bazra, Maize, Green gram, Red gram, Black gram.
Commercial crops: Sugarcane, Jute, Chillies, Cotton, Turmeric.
Forest based Resources: Plantation of Eucalyptus Trees, Ponuku wood, Casuarina,
Subabul, Jatropa, Pongamia (bio – diesel plantation).
And also:
Vegetables, flowers, plantation crops, spices and medicinal plants, aromatic crops.
They occupy 6517, 177, 4440, 14315 and 369 hectors respectively in Khammam District.
Local Fauna:
Life Stock Resources: Poultry, Dairy form.
Marine Resources: Fish, Prawn.
Animal Husbandary: Plough animals, Dairy animals like Cow, Buffaloes, Sheep, Goat, Pig.
Forest resources:

1. Panther, Hyena, Jungle cats, Foxes, Bears, and Carnivores, Mammalian are found.
2. Deer, Spotted deer, Sambar, Black buck and other Herbivorous animals found in inland forests.
3. The district has a large number of murrah buffaloes and cows.
4. Migrant grey billed pelican is a protected bird in Kolleru lake and Pulicat lake.

Question 13.
Where do you find most of the biodiversity on the earth? Draw A.P map showing maximum biodiversity areas.
Answer:

1. In areas with sufficient amount of water, a wide variety of plants ranging from grasses to tall trees are seen.
2. Most of the forests are seen in these areas.
3. As there is sufficient vegetation, there will be a large number of herbivorous animals. Carnivorous animals which feed on the herbivores are also found in these regions.
   
4. Generally there is a increase in biodiversity from poles to trophies. Thus localities at lower lattitudes have more species than localities at higher lattitudes.
5. Ultimate factor behind many of the other factors is greater mean temperature at the equator.

Question 14.
What do you understand by biodiversity? How can you say variations are present in them?
Answer:
The word biodiversity is a contraction of biological diversity. It is commonly used to describe the number variety and variability of living organisms. This very broad usage embracing many different parameters, is essentially a synonym of LIFE ON EARTH.

1. The whole world has wide variety of living organisms we can see both invisible (microbial) and the visible world around us are diverse.
2. Different microorganisms like algae, fungi, bacteria, viruses etc., and also the micro-arthropods. There is diverse among microbes.
3. There are different variety of plants like grass, herbs, shrubs, creepers, trees etc. Among the individuals also there are variations like height, colour and size of flower and fruits.
4. We find variations in animals even though they are similar kind. We find differences in colour of fur, nails, claws or hoofs etc.
5. Among birds we can see variations in their feathers, feet, crown, tail etc.
6. As all the humans belong same genus but there is variation in their hands, fingers, toes, nails and hair, height and shape. We can even see variation in the texture of skin dry, oily, smooth or rough. Whether they are twins also we can find variations among them.

Question 15.
Most of our biodiversity is being lost due to human activities. Suggest few ways to protect them.
Answer:
Most of our biodiversity is being lost due to human activities like logging of wood, increased agriculture, increased human habitation and pollution etc. Man has realised this mistake before it was too late. Government of India also realised the importance of wild life and initiated several programmes to preserve wild life in the country and the wild life act was passed in 1972.
Efforts towards conservation:

1. Activities leading to deforestation have been declared as illegal activities and severe punishments have been imposed.
2. Pouching of birds and hunting their eggs are prohibited.
3. Usage of pesticides should be minimised. Usage of biological control methods of pests should be maintained.
4. Efforts to be made to substitude chemical fertilizers with more (natural) bio fertilizers.
5. Pollution from the industries should be reduced.
6. Automobiles should be designed to reduce pollution.
7. Reforestation programmes will be conducted.
8. Gardens, parks, lakes and zoos should be developed.
9. National parks, wild life sanctuaries, where wild life is protected, have been created.
10. Collection, marketing and selling of forest products such as sandal wood, ivory by private parties is banned and is taken up by the Government.
11. Construction of cell phone towers which produce radiation, should be in greater height, so that they should not be reachable to the birds.

Question 16.
When you see a park, sanctuary or a zoo with many kinds of plants and animals, how would you express your happiness? Write a few lines on them.
Answer:

1. Imagine a forest with a carpet of wet leaves littering the ground, the flowers on the trees, we can hear the water drops, sounds of insects, birds chirping and perhaps the distant screech of a monkey – the place picturing is a park, a sanctuary or a zoo. Which gives pleasure to us.
2. These are the homes for many plants and wild animals – and also decorate the world. Any of them are airy and shadowy places.
3. These dwelling places of plants and animals give us happiness. When we are in distress. They give relax – when we feel tired. They give us enjoyment when playing with our friends and they give good health – when we fall sick as they give fresh air and are the lungs of the world.
4. They maintain ecological balance in the environment where we live.
5. We notice the pet dog licks our feet, wags it’s tail, sits near us and walks with us we feel the affection, which gives pleasure mentally.
6. Like this we can experience many situations plants and animals as they are the partners of our environment. So be kind towards them and protect the environment. By maintaining eco – friendly activities.

Question 17.
Prepare an essay to give a talk on biodiversity and conservation.
Answer:

1. The existence of biodiversity in nature teaches us that every plant and animal whether useful or not has right to exist on earth.
2. Every organism is a part of our ecosystem. Loss of any organism endemic or otherwise effects the food chain and food web of that ecosystem, which has impact on the world biodiversity.
3. Hence if we want to protect the biodiversity on our planet, first we must be a part of conservation and then make other aware of it because today we see extinction of some species tomorrow it could be our species.
4. Conserving the biodiversity in a wider prospective is utilizing the forest resources judiciously without affecting the ecosystems so that we can have a sustainable development in the forests and the biodiversity can be conserved for future generations.
5. Nature is for human’s need, not for his greed. If we protect nature, it protects us.

Question 18.
Rani said conservation, of biodiversity starts from our home. Is she correct? How do you support Her? What will be your action for this?
Answer:

1. We live in houses that protect us from heat, cold and rain etc.
2. We keep some animals and birds as pets in our houses. We also grow some plants which give us fruits and vegetables.
3. Thus we can say that our house is also a habitat. Several animals like dogs, cats, goats, cows, birds, hens, ducks, pigeons, spiders, ants, cockroaches live with us.
4. Plants like money plant and some crotons are also kept inside our house.
5. We know that every bit of effort towards conservation helps. If we take due care of plants growing around us, we may not be adding a forest, but adding to greenery around us which is essential for our own existence.
6. So Rani is correct. Conservation of biodiversity starts from our house.

Question 19.
When we take steps towards conserving the tiger, what are the other things that have to be conserved?
Answer:

1. When we take steps towards conserving the tiger we have to conserve the other flora and fauna related to the tiger.
2. If a tiger has to be saved it’s food web should be protected.
3. The tiger depends for food on deer and many other herbivores.
4. If the tiger disappears, the deer and other herbivores population will increase and that would affect the flora of the area.
5. All organisms in nature influence each other in some way or the other. So we need to protect all of them.

Question 20.
Prepare some slogans or a pamphlet to make aware of people about conservation of biodiversity. (OR)
Prepare two slogans to conserve biodiversity in your area.
Answer:

1. Save tree – Save other lives too.
2. Save the lungs of the earth.
3. Be kind towards biodiversity.
4. Reduce pollution.
5. Protect Nature, it protects us.
6. Nature is for human’s need not for his greed.
7. Hunting of wild life is a crime.
8. Forest is our life.

8th Class Biology 6th Lesson Biodiversity and its Conservation InText Questions and Answers

Question 1.
Rampachodavaram: East Godavari District, 60-70 years back Rampachodavaram had dense forest with a rich heritage of wild life. These forest extended to border areas of Aswaraopet of West Godavari district. It was an abode for wild animals like tigers, leopard, deers, hyenas (kondrigallu), foxes, wild boars (adavi pandi), bears, pythons, cobras, porqupines (mulla pandhi), owls, hares, monitor lizard (udumu) scorpions, geremandals (like the desert spider) etc.
After the erection of mines (colour soil) and other industries, human activities increased. Then many buildings, roads and stone quarries have come into exist¬ence. Forest area was cleared and so several organisms started disappearing.
Though an area near Maredumilly, Addateegala (very close to Eleswaram) was once known as Tiger valley, shows no signs of tigers now. Animals like foxen, deers are also not seen these days.
Now there are several human settlements in the area. Some areas of less dense forests with animals like pythons, cobras, deers, scorpions etc., are commonly seen. Bears are rarely found. Peacocks have been sighted recently.
The above case study explains you the need of conservation of biodiversity.
a. What is the difference between the situation regarding types of animals present 70 years ago and now?
Answer:
70 years ago Rampachodavaram had dense forest with a rich heritage of wild life. Now no animals are not seen. Now there are several human settlements in that area.

b. What might have happened to tigers of Rampachodavaram?
Answer:
After the erection of Mines (colour soil) and other industries, human activities increased. Many buildings, roads and stone quarries have come into existence. Forest areas were cleared and so several organisms started disappearing.

c. Do we find tigers any where else in our country?
Answer:
Tigers are found in other parts of our country and the world as well.

d. Peacocks love eating snakes. Can you guess why they dwell in this place?
Answer:
We can find snakes in desert areas. Peacocks love eating snakes. So they dwell in this place where it finds it’s food (snakes) plenty.

Question 2.
Is there any extinct species in your area ? Name them and write a note on them.
Answer:
Sparrow, Vulture.
i) Over use of pesticides and radiation from cell phone towers led to extinction of sparrow.
ii) By feeding of diclofenac – treated cattle led to extinction of vulture.

Question 3.
Give your reasons as for why the organisms become so extinct?
Answer:

1. Either knowingly or unknowingly, man has destroyed the wild life.
2. Hunting of animals either for food or for pleasure, cutting of trees and clearing of forests for fuel, timber and for human settlements, construction of dams and reservoirs has resulted in large scale destruction of forests. This has destroyed the wild life.

Question 4.
How biodiversity is depleting in your area? How to improve it?
Answer:
Biodiversity depleting: Reduction of plant and animal species is called biodiversity depletion. Causes:
1) It may be caused by natural causes which include floods, earthquakes, land slides, diseases etc.
2) Man made causes are called ‘Anthropocentric’ causes. These are

1. Urbanization
2. Expansion of agriculture
3. Deforestation
4. Pollution

In my area: Lot of animal species are in danger of depletion in may areas due to human activities. Sparrow’s, voltures, become rare ones. Their population decreased rapidly.
How to improve?

1. Give importance to plantation
2. Avoid deforestation
3. Installing bird boxes
4. Protect the native species
5. Provide wild life corridors
6. Use organic manures
7. Utilise existing green space connections
8. Be mercy with other creatures.

Question 5.
Observe the pictures and identify the animals. Also try to find out where these can be found.

Answer:
1. Peacock – India (It is our National bird)
2. Tiger – India (It is our National animal)
3. Kiwi – Newzealand

Question 6.
Name an Endemic species of our state.
Answer:
Indian lion, Leopard.

Question 7.
Why should we conserve a small insect like a bee or butterfly?
Answer:
The insects like bee and butterfly, suck nectar from the flowers. By this pollination takes place in flowers.

Question 8.
What will happen if these insects become extinct?
Answer:
Insects help in pollination of flowers. By this pollination fertilization of flowers takes place and seeds will form which helps in the growth of next generation of plants. If insects become extinct – no pollination – no fertilization and no future generations of plants, there by extinction of plants takes place.

Question 9.
What can be done to save these insects?
Answer:
Spraying of pesticides will be minimised. Biological Methods will be used to control pests. (The animals which feed on pests will be used in the agricultural lands.)

8th Class Biology 6th Lesson Biodiversity and its Conservation Activities

Activity – 1 & 2

Question 1.
How many different colours could you mark on your sheet?

Answer:
Seven different colours. (Refer textbook page 85 for colours)
i) What does the colours indicate?
Answer: The colours indicate the existence of plants, animals, insects, humans, and birds,
ii) What does your total colour code count indicate?
Answer: Plants, animals, birds, insects live in our surroundings.
iii) What are the things that attract you very much in the nature?
Answer: Bird’s nests, cobwebs, worms, leaves, insects, mosses etc attract us.
iv) Write your feelings without any hesitation.
Answer: Enjoyment, happiness and pleasure.

Activity – 3

Question 2.
Variations in plants.
Answer:

Similarities:

1. Paddy and Maize belong to grass plants.
2. Both of them have same root system (fibrous R.S.)
3. They are green colour.
4. Seeds are enclosed.
5. They produce cereals.

Variations in Animals:
a) Do you find any differences between animals?
Answer:
They show difference in colour of fur, nails, claws, hoofs etc.

b) Do you find any differences among birds?
Answer:
Birds have differences in their feathers, feet, crown, tail etc.

Variations in Human beings:
a) Observe two students of your class. Do they appear similar?
Answer:
No. Human beings show differences in their height & shape, hands, fingers, toes, nails and hair.
The texture of skin also may be dry, oily, smooth or rough.

b) Suppose two of your classmates happen to be twins, will they look same in structure and shape.
Answer:
If they are twins also we find little differences.

Activity – 4

Question 3.
Collect and paste some pictures of your favourite cricket players belonging to countries like West Indies, Australia, India, etc. in your note book.
Write the differences and similarities that you have noticed in them. What diversity you observed?
Display your finding of above activity in the class and discuss the following questions.
a) Are there any two organisms with 100% similarities between them?
Answer:
No, there are no organisms with 100% similarities.

b) Why do they differ from each other?
Answer:
Because they belong to different species.

c) What will happen if all plants are creepers?
Answer:
If all plants are creepers there will be no shelter for many birds and animals.

d) Hen and goat both have legs. What diversity do you find between them?
Answer:
Hen is a bird and goat is an animal. So hen has two legs and goat has 4 legs.

e) Are all the nests of birds similar why?
Answer:
Because of their living conditions and food habits, the nests of birds are not similar.

f) Do animals all around the world have similar organs and functions? What is the diversity behind them?
Though they look similar, upon careful observation we find differences or variations between them that leads to Biodiversity.

There is no mononamy or uniqueness in structure and functions of nature.
Diversity is the nature’s way.

Activity – 5 (Project work)

Question 4.
Studying migration and its effect on biodiversity of an area.

Read the following ways to conserve biodiversity try to enrich this list in your own way.
1. Look at the sky in the morning and evening. Do you observe birds flying in groups ?
Answer:
Yes. We can see birds flying in the sky in the morning and evening in groups.

2. Did you get the same number and types of birds every day?
Answer:
No. Some times more and some times less in number.

3. Was there any sudden variation in a particular season?
Answer:
Particularly in winter season we can see large number of birds flying in the sky.

4. Did you notice any new type of bird population in any season?
Answer:
During rainy season most of the birds from far away places migrate to Kolleru and Pulikot lakes of our states.

5. Why do these birds move from one place to another?
Answer:
Birds move from one place to another for food and shelter (nestling habits)

6. Sometimes at night we see birds flying in groups. Where do you think they fly to?
Answer:
Sometimes to protect themselves from climatic conditions, for food, for reproduction and to escape from hunting and also due to deforestation, we see birds flying in groups.

7. Perhaps the most important value of biodiversity, particularly in a country like India. Is that it meets the basic survival needs of a vast number of people.
Answer:
Cereals, pulses, oil seeds, sugars, spices, drugs, fibres, coir, timber, resins, gums, fruits, vegetables, dyes are obtained from plants. Meat, skin and hair are obtained from animals.
Like this the biodiversity in our country meets the basic survival needs of a vast number of people.
Flora and Fauna are renewable resources and are to be use judiciously.

Activity – 6 (Project work)

Question 5.
How to make recycled newspaper from waste newspapers? (OR)
Write the procedure of preparation of recycled paper which you did in your school lab.
Answer:
Materials:
2 plastic tubs, wooden spoon, water, clean cotton cloth, old news paper, wire screen, measuring cup, plastic wrap, blender, heavy books / roller.
Procedure:

1. Add cut news papers strips in a tub full of water and soak it for a day.
2. Put two cups of soaked paper and six cups of water in a blender. Blend till the mixture turns into a pulp (like nanny oat meal).Pour it in a clean tub.
3. Fill the tub with one fourth of blended paper pulp.
4. Lay a cloth on a flat, waterproof surface. Slide the wire screen under the wet paper. Remove the screen gently. Press the news paper pulp to squeeze out any extra water.
5. Carefully flip the screen onto the cloth. Press it down firmly. Remove the screen.
6. Lay another cloth on top of the mixture. Cover the cloth with a plastic wrap and stack the books on the wrap.
7. After several hours remove the books on the cloth and let the paper dry.
8. You can even use a hair dryer to blow the paper dry.
9. By adding few drops of edible colours to the pulp you can make your paper colourful. Iron the new made paper with a iron box and cut it to your required size and shape.
10. Beautiful greeting cards, file covers, bags etc., can be made using recycled paper.

Question 6.
How is a compressed cardboard prepared?
Answer:
Materials: bits of wood, saw dust and chemicals sulphate.
Producer:

1. The pulp is made by using bits of wood.
2. It is spead evenly as layers.
3. The saw dust is sandwiched between the two layers.
4. This is compressed and dried.
5. It becomes hard and strong as wooden board.
6. Hence there is no need to cut down the whole tree. This helps in reducing deforestation.