TS 8th Class Physical Science Study Material 4th Lesson Synthetic Fibres and Plastics

TS Board Telangana SCERT Class 8 Physics Solutions 4th Lesson Synthetic Fibres and Plastics Textbook Questions and Answers.

TS 8th Class Physics 4th Lesson Questions and Answers – Synthetic Fibres and Plastics

Reflections on concepts

Question 1.
Explain about ductility.
Answer:
The property of drawing a material to make fine wires is known as ductility. Most metals are ductile. Arsenic and antimony metals are non-ductile.

Question 2.
Explain the physical properties of metals with suitable examples.
Answer:
Following are the physical properties of metals –

  1. Physical state; All metals are solids at room temperature. Eg: Gold, silver, iron. But the metals mercury and gallium are liquids at room temperature.
  2. Lustre: Metals possess metallic lustre. When cut or polished, metals shine brightly.
  3. Malleability: Metals are malleable. Eg: Gold is very highly malleable. They can be hammered into thin sheets.
  4. Ductility: Metals are ductile. They can he drawn into very fine wires. Eg: Copper wires.
  5. Hardness: Metals are generally hard. But there are some exceptions. Sodium, potassium. calcium, lead etc., are soft metals.
  6. Density: Metals generally have high density. But metals like sodium, potassium have low density.
  7. Melting and boiling points: Metals have generally high melting and boiling points. Metals like sodium, potassium, mercury have low m.p and b.p.
  8. Sonority: Metals produce sound when they hit a hard surface. It means metals are sonorous.
  9. Conductivity: Metals are very good conductors of heat and electricity. But tungsten is a poor conductor of electricity. So it is used in Lamp filaments.
  10. Solubility: Metals are generally insoluble in water and other solvents. Metals like sodium, potassium, calcium dissolve in water. By chemically reacting with water, new products are liberated.
  11. Formation of alloys: The capacity of a metal to combine with other metals (and sometimes, non-metals) is called ‘alloy formation’.

Metals form alloys. Eg: brass, bronze, steel. Metals like copper, silver, gold, and zinc dissolve in the liquid metal, mercury. Then alloys are formed. These are called, amalgams’.
Eg: Zinc amalgam, Gold amalgam, etc.
(Zn + Hg) (Au + Hg)

Question 3.
Draw the diagram of identifying electric conductivity of a material.
Answer:
TS 8th Class Physical Science Study Material 4th Lesson Synthetic Fibres and Plastics 1

Question 4.
Which gas makes a Pop Sound when it exposed to lighted match stick?
Answer:
Hydrogen gas.
Reason: Hydrogen combines with the oxygen of air to form water. This reaction is quite vigorous. Heat is liberated then. This heat energy appears as sound energy. Hence we hear a ‘pop’ noise when a lighted match stick is exposed to hydrogen gas.

TS 8th Class Physical Science Study Material 4th Lesson Synthetic Fibres and Plastics

Question 5.
Gold jewellery does not become dull. Why?
Answer:
Gold does not chemically react with the components of air. So the metal does not lose its shining, even on long exposure to air. It does not become dull. Draw the diagram of identifying electric conductivity of a material.

Application of concepts

Question 1.
If you are given two samples, how do you distinguish which one is metal and which is non-metal’?
Answer:
The two samples may he metals or both, non-metals. One of them may he a metal and the other, a non-metal. Hence, both the samples should be tested and then decided.

Sample I:

  1. It is a solid.
  2. On rubbing with a sandpaper, it shined.
  3. It is hard.
  4. When dropped on the hard floor, it produced a little sound.
  5. It stretched when hammered.
  6. It is not soluble in water.
  7. On igniting, it burnt with a dazzling light. A white ash is formed.
  8. The ash is shaken with a little water.
  9. The solution turned red litmus, blue.

The above properties confirm, that this sample is a metal.

Sample II:

  1. It is a yellow powder.
  2. It is soft.
  3. It produced no sound when hit with a metal spatula (non-sonorous)
  4. It is not soluble in water.
  5. On heating, it produced colourless gas with suffocating odour.
  6. The gas turned moist blue litmus red, so it is an acidic oxide.
  7. Since the oxide is acidic, the sample is a non-metal.

The above properties confirm, that this sample is a non-metal.

Question 2.
Which metals are used in making jewelry? Why?
Answer:
Gold, Silver and Platinum are used in making jewellery.
Reason: These metals do not react with the components of air. So the jewellery made of gold and platinum does not lose its shining. It does not become dull. Silver tarnishes in air. It means the metal gets coated with a thin black film. So it becomes dull. Hence its use in jewellery is restricted.

Question 3.
Why don’t cooking pans have metal handles?
Answer:
Metals are good conductors of heat and electricity. So the handles of cooking pans are not made of metals. If they are made of metals, they also get heated up, along with the pan. Then we cannot handle the pan.

Question 4.
How do you appreciate the efforts of man to use the metals in making tools?
Answer:

  • Early human beings made their tools from stone and wood which were easily available.
  • Later they used the bones of animals.
  • Then they discovered metals like copper and iron.
  • Metals had the advantages of not just being harder but they can be heated in fire and moulded or cast into different shapes.
  • So it became possible to make a wider range of tools with metals.
  • So I appreciate the efforts of man to use the metals in making tools.

Question 5.
Why the bells are made by metals instead of wood?
Answer:
Bells should produce a ringing sound when hit by a hard substance. Only metals produce such sound. Metals are sonorous materials. So bells are made up of metals instead of wood. Wood does not produce a ringing sound. It is not a sonorous material.

TS 8th Class Physical Science Study Material 4th Lesson Synthetic Fibres and Plastics

Higher Order Thinking Questions

Question 1.
Dumping of waste material made up of metals and non-metals leads to environmental pollution. Do you support the statement? Give your justification with suitable\ examples.
Answer:
Possible doubts in my mind:

  1. Non-metals like sulphur, phosphorus, carbon etc. are soft. But diamond is hard. Why?
  2. Non-metals do not shine. They appear dull. But diamond glitters. Why?
  3. When metals are polished, they shine. Diamond also glitters. So why can’t diamond be a metal?
  4. Metals and non-metals are elements. Is diamond really an element, or is it a compound?
  5. ‘Diamond’ is not included in the list of names of all known metals and non-metals. Then what is it? 1f it is a non-metal, why is it not included in the list of names of known non-metals?

Question 2.
In a chemical reaction iron is unable to displace zinc from zinc Sulphate.Why?
Answer:
A less reactive metal cannot displace a more reactive metal from its salt solution. Iron is less reactive than zinc. So iron cannot displace zinc from zinc sulphate solution. Zinc sulphate + Iron → No reaction. (We do not get zinc)
(Note: Metal activity series is Al > Zn > Fe ………….. . )

Question 3.
How the property malleability of metals is used in our daily life?
Answer:
1. A thin silver foil is used to decorate sweets.
2. Thin aluminium foil is used in inner packing of food materials and toffees.
3. A blacksmith beats a hot iron piece till he gets the desired shape. He thus makes some agricultural instruments.
4. Many decorative materials are made of metals, due to their malleability.

Question 4.
Dumping of waste material made up of metals and non-metals leads to environmental pollution. Do you support the statement? Give your justification with suitable examples.
Answer:
All materials are chemical substances made of metals and non-metals. The chemical
substances in the waste material sometimes become the source for different types of pollutions, like air pollution, water pollution, soil pollution etc.

1. Air pollution: Oxides of carbon, oxides of nitrogen and oxides of sulphur released by the gradual decay of the waste material, pollutes the air.

2. Water pollution: Water is polluted by the wastes discharged by industries and houses.
industrial wastes contain metals like mercury, cadmium, lead etc, along with some organic compounds like phenols, alkalies, etc. All these pollute water.

The sewage from the houses is the dirty water containing organic compounds. These are harmful to aquatic living beings, like fish.

3. Soil pollution: Soil is polluted by the excessive use of fertilizers, insecticides and herbicides. Because of atmospheric pollution, acid rains also result, This damage the soil and the green vegetation on the earth.

Question 5.
How do you appreciate wide range utility of aluminium right from utensils to space crafts?
Answer:
The physical properties of aluminium made it a very important material, used in the manufacture of a wide variety of articles.

Properties of Aluminium Uses of Aluminium
1. Light, a good conductor of heat and electricity. Manufacture of electrical wires, cables for transmission lines and winding moving coils of dynamos and motors.
2. Aluminium powder + linseed oil Used in silvery-white paints and lacquers.
3. Cheap, good appearance and a good conductor of heat. To make water baths, air baths, cooking and other household utensils, trays etc.
4. Highly malleable Used to make Aluminium foils used in wrapping cigarettes, chocolates and sweets.

Alloys of aluminium are light with a high tensile strength. They are resistant to corrosion. So these alloys are used in making domestic utensils, jewellery, parts of aeroplanes, aeroplanes, airships, etc. So I appreciate wide range utility of aluminium right from utensils to spacecraft.

Multiple Choice Questions

Question 1.
Sulphur dioxide, by nature, is [ ]
a) Basic oxide
b) Acidic Oxide
c) Neutral Oxide
d) Dual Nature oxide
Answer:
b) Acidic Oxide

Question 2.
Maximum metals are obtained in the state of [ ]
a) Liquid
b) Solid
c) Gaseous
d) Plasma
Answer:
b) Solid

Question 3.
Some metals react with acids and evolve [ ]
a) Hydrogen
b) Oxygen
c) Carbon dioxide
d) Nitrogen
Answer:
a) Hydrogen

TS 8th Class Physical Science Study Material 4th Lesson Synthetic Fibres and Plastics

Question 4.
Generally, non-metallic oxides are by nature [ ]
a) Basic
b) Acidic
c) Neutral
d) Dual
Answer:
b) Acidic

Suggested Experiments

Question 1.
Conduct an experiment to know the reaction of Oxygen with metals and non-metals.
Answer:
Aim: To know the reaction of oxygen with metals and non-metals
Material required: Two metal samples (copper and magnesium) and one non-metal sample (sulphur), spirit lamp or bunsen burner and litmus papers, etc.

Procedure:
i. Take a piece of copper wire. If the wire is covered with plastic then remove it with sandpaper or pliers. Note the colour of the wire. I fold the wire with a pair of tongs and heat it for some time over a spirit lamp or bunsen burner. Cool the wire and note the colour.

ii. Take a small strip of magnesium and note its appearance. Burn it. Collect the ashes of magnesium in a test tube and add some distilled water to it. Test the solution with red and blue litmus papers.

iii. 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 tumbler. Cover the tumbler with a lid to ensure that the gas produced does not escape.

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 papers.

iv. Note the results of above activities in a table.

Sample Appearance before reaction Appearance after reaction Effect on moist litmus paper
Copper Shiny, reddish brown Black powder, Coating
Magnesium Silvery white White ash Red → Blue
Sulphur YeIlow Colourless gas Blue → Red

From these activities, we can conclude that
a. Non-metals react with oxygen to give out oxides that are acidic in nature.
b. Metals react with oxygen to give out oxides that are basic in nature.

Question 2.
The nature of oxides helps to identify the metals and non-metals. Conduct an experiment to prove this and record the observations.
Answer:
. Experiment-I:

  • Get a strip of magnesium ribbon and hold it on flame with the help of a pair of tongs.
  • Magnesium ribbon burns in air with a brilliant flame to form magnesium oxide a white powder.
    2 Mg +O2 → 2MgO
  • Add some water to magnesium oxide and prepare its solution.
  • Test the solution with blue and red litmus papers.
  • The solution turns red litmus to blue. So, the solution is basic in nature.
  • From this we conclude that, if the solution of oxide turns red litmus to blue, then that oxide is metallic oxide.

Experiment-2:

  • Take a deflagrating spoon-keep some heated sulphur on the spoon in a jar full of oxygen.
  • Sulphur burns with a flame-producing pungent-smelling gas. This is SO2.
    S +O2 → SO2
  • Pour a little water into the jar and shake it to dissolve the gas in water.
  • On dissolving. SO2 gas forms a solution with water.
  • Test the solution with litmus papers.
  • It turns the blue litmus to red. Thus the solution is acidic in nature,
  • From this, we conclude that, if the solution of oxide turns the blue litmus to red, then it is a non-metallic oxide. From the above two experiments, the nature of oxides helps to identify the metals and non-metals.

Question 3.
Identify the electric conductivity of materials with an experiment.
Answer:

  1. Arrange an electric circuit with a battery and bulb Close the circuit using an iron nail, zinc, copper, sulphur, aluminium, graphite, magnesium and iodine samples.
  2. Observe whether the bulb glows or not.
  3. Record your observation in the given table about glowing a bulb.
  4. If bulb glows, the used sample is a conductor. If bulb does not glow, sample is bad conductor of electricity.

TS 8th Class Physical Science Study Material 4th Lesson Synthetic Fibres and Plastics 2

Sample Bulb glows (Yes/No)
Iron Yes
Zinc Yes
Copper Yes
Sulphur No
Aluminium Yes
Graphite Yes
Magnesium Yes
Iodine No

TS 8th Class Physical Science Study Material 4th Lesson Synthetic Fibres and Plastics

Suggested Projects

Question 1.
Collect the information about metals which we use in our daily life, and their uses. Write a report on it.
Answer:

Metals Their uses
Gold Jewellery
Silver Jewellery
Copper Jewellery, utensils, electrical appliances
Aluminium Utensils, packing of food, parts of aeroplanes and satellites
Mixture of Al & Cu Currency coins, medals and statues

Question 2.
Imagine the human life without metals. Write a report.
Answer:
In the absence of metals, the Stone Age repeats, when the extraction and the use of metals was unknown. Metals play a very important role in the modem world. In their manufacture, right from a pin upto the space rocket, metals are used. The bicycles, motor bikes, motor cars, railway vehicles, aeroplanes, are all made of metals and alloys. The filaments in ifiament bulbs, lanterns, electric poles, wires etc. are all made of metals.

The chairs, tables, cots etc are mostly made of metals. The spoons, plates, utensils, cooking stoves, gas cylinders, cookers, etc. are all made of metals. The printing machine, some parts of a pen are all made of metals.

In the absence of metals, there will be no industries, no work to people. People lose their livelihoods. When no alternatives replace a metal, human life on earth becomes miserable.

TS 8th Class Physics 4th Lesson Synthetic Fibres and Plastics Intext Questions

Think & Discuss

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! (Text. P. No. 56)
Answer:
1. A large iodine crystal should be taken. It should be placed on a strip of paper and used
directly for the purpose.
TS 8th Class Physical Science Study Material 4th Lesson Synthetic Fibres and Plastics 3

2. A vial (a small empty injection bottle) is taken and filled tightly with powdered iodine or sulphur. Two holes are made in the rubber stopper. The ends of the wires are passed through the holes and dipped in the powder.
TS 8th Class Physical Science Study Material 4th Lesson Synthetic Fibres and Plastics 4

TS 8th Class Physics 4th Lesson Synthetic Fibres and Plastics Activities

Activity- 1 :
Observing the appearance and colour of some materials :(Text. P. No. 53)

Question 1.
Observe the metals around you. Observe their colour and appearance and tabulate your observations.
Answer:
I observe some metals and tabulate my observations as

Sample Appearance shining/ not shining Colour
Iron (Pure) shining Silvery white
Zinc shining Bluish white
Copper shining Reddish
Sulphur not shining Pale yellow
Aluminium shining White with bluish tinge
Graphite slightly shining Dark grey
Magnesium shining Silvery white
Iodine shining Black

Questions based on the above Activity -1
a. Which of the samples did not shine even after you cleaned them with sandpaper?
Answer:
All the metals shined after cleaning them with a sandpaper. Brittle and soft powders cannot be cleaned like the above.

b. Generally metals are lustrous. Do all lustrous materials are metals? Can a mirror be called metal?
Answer:
All lustrous materials are not metals. Mirror is lustrous hut it is not a metal.

TS 8th Class Physical Science Study Material 4th Lesson Synthetic Fibres and Plastics

Activity – 2 :
Listening the sound Produced by some material: (Text. P. No. 53)

Question 2.
Explain an activity to show that metals are sonorous.
Answer:
Sonorous: The ability of materials to produce a particular sound when it is dropped on the hard surface is called as sonorous.

Take the samples of zinc, copper, sulphur, aluminium, graphite, magnesium and iodine. Drop them one by one, on a hard surface. Listen carefully to the sound produced and record your observation in table.
Table

Material sample that produces sound Material sample that does produce sound
Zinc Sulphur
Copper Graphite
Aluminium Iodine
Magnesium

From the above activity, we conclude that metals produced sound when they are dropped on a hard surface. So metals are sonorous materials.

Questions based on the above Activity -2
a. Do you think coal is sonorous?
Answer:
Coal is not sonorous. Because it does not give sound when it dropped.

b. What similarity do you notice among materials which produce sound?
Answer:
Most of the metal materials produce sound when they dropped on hard surface.

c. Which property of metals first attracted the attention of human beings? The story of early tools will give you a hint.
Answer:
A property, the tensile strength of metals first attracted the attention of human beings.

Activity -3: Identify malleability of material: (Text. P. No. 54)

Question 3.
What is malleability? Conduct an activity to verify the malleability of materials.
Answer:
The property of metals by which they can be beaten into thin sheets or foils is called malleability
i. Take a hammer and beat the material samples and observe the changes in material samples. Record your observations in the table.

Observing the change Name of sample
Flattens Iron, copper, aluminium, magnesium and zinc
Break’ converts into powder Graphite, Iodine
change

ii. From the above table we conclude that some materials can be flattened into thin sheets and some do not.
iii. Malleability range is different for different metals.
iv. Aluminium, silver and gold are highly malleable.

Activity -4 :
Identifying electric conductivity of a material: (Text. P. No. 56)

Question 4.
What are conductors of electricity? Conduct an activity to verify the electric conductivity of materials.
Answer:

  • Arrange an electric circuit with a battery and bulb
  • Close the circuit using an iron nail, zinc, copper, šulphur, aluminimum, graphite, magnesium and iodine samples.
  • Observe whether the bulb glows or not.
  • Record your observation in the given table about glowing a bulb.
  • If bulb glows, the used sample is a conductor. If bulb does not glow, sample is bad conductor of electricity

TS 8th Class Physical Science Study Material 4th Lesson Synthetic Fibres and Plastics 5

Sample Bulb glows (Yes/No)
Zinc Yes
Copper Yes
Sulphur No
Aluminium Yes
Graphite Yes
Magnesium Yes
Iodine No

TS 8th Class Physical Science Study Material 4th Lesson Synthetic Fibres and Plastics 6
Questions based on the above Activity – 4

a. Talk to an electrician. Look at the handles of his tools. Are the handles made of the same materials? If not why?
Answer:
No. Some handles are made of wood. Some others are made of plastic. The two factors wood and plastic are bad conductors of electricity.

b. What do cooking appliances conduct?
Answer:
Cooking appliances conduct heat.

TS 8th Class Physical Science Study Material 4th Lesson Synthetic Fibres and Plastics

Activity- 5:
Observing conduction of heat by metals: (text. P. No. 56)

Question 5.
What is meant by conduction of heat? How do you prove the conduction of heat by metals? (Conceptual understanding/Experimentation)
Answer:
The property of a substance which moves heat from one end to the other end through it Is called heat conduction.

  • Take an iron rod, stick pins on it with the help of wax.
  • Now fix the rod to a stand. Heat one end of the rod with a spirit lamp and observe the pins fall off.
  • The pin fell off because of the heat supplied to the iron rod makes the wax to melt at one end.
  • The wax closer to the flame melted first.
  • This activity shows that heat moves From one end of the object to the other end.
  • This property of a material is known as heat conduction. All metals are good conductors of heat.

Questions based on the above. Activity -5

a. Why did the pins fall off from iron rod?
Answer:
Iron is a metal. It conducts heat. When one end of the rod is heated, heat is conducted throughout the whole length of the rod. Then the whole rod becomes hot. Then wax melts and it loses grip over the pins. So the pins drop-down, due to earth’s gravity.

b. Pin of which end fell off first?
Answer:
The pin nearer to the flame falls first.

c. What could be the reason for this?
Answer:
Conduction of heat is not a sudden process (unlike electricity). It takes some time for the heat to flow from the hot end to the colder end. So the end of the rod nearer to the flame becomes hot, first. Then the pin nearer to that end loosens and drops down.

Question 6.
Collect some sample of metals and non-metals, Observe the properties of lustrous, sonorous, conduction heat, electricity, malleable and ductile nature. identify the metals and non-metals. (Text. P. No. 57)
Answer:
Table-6:
TS 8th Class Physical Science Study Material 4th Lesson Synthetic Fibres and Plastics 7
Metals: iron, Zinc, Copper, Aluminium, Magnesium.
Non-metals: Sulphur, Iodine, Graphite (metalloid)

Lab Activity

Question 1.
Conduct an experiment to know the reaction of oxygen with metals and non-metals.
Answer:

Aim: To know the reaction of oxygen with metals and non-metals
Material required: Two metal samples (copper and magnesium) and one non-metal sample (sulphur), spirit lamp or bunsen burner and litmus papers, etc.

Procedure:
i. Take a piece of copper wire. If the wire is covered with plastic then remove it with sandpaper or pliers. Note the colour of the wire. I fold the wire with a pair of tongs and heat it for some time over a spirit lamp or bunsen burner. Cool the wire and note the colour.

ii. Take a small strip of magnesium and note its appearance. Burn it. Collect the ashes of magnesium in a test tube and add some distilled water to it. Test the solution with red and blue litmus papers.

iii. 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 tumbler. Cover the tumbler with a lid to ensure that the gas produced does not escape.

TS 8th Class Physical Science Study Material 4th Lesson Synthetic Fibres and Plastics

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 papers.

iv. Note the results of above activities in a table.

Sample Appearance before reaction Appearance after reaction Effect on moist litmus paper
Copper Shiny, reddish brown Black powder, Coating
Magnesium Silvery white White ash Red → Blue
Sulphur YeIlow Colourless gas Blue → Red

From these activities, we can conclude that
a. Non-metals react with oxygen to give out oxides that are acidic in nature.
b. Metals react with oxygen to give out oxides that are basic in nature.

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