AP Board 9th Class Physical Science Solutions Chapter 3 Is Matter Pure?

AP State Syllabus AP Board 9th Class Physical Science Solutions Chapter 3 Is Matter Pure? Textbook Questions and Answers.

AP State Syllabus 9th Class Physical Science Solutions 3rd Lesson Is Matter Pure?

9th Class Physical Science 3rd Lesson Is Matter Pure? Textbook Questions and Answers

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Question 1.
Which separation techniques will you apply for the separation of the following? (AS 1)
a) Sodium chloridfe from its solution in water.
b) Ammonium chloride from a mixture containing sodium chloride and ammonium chloride.
c) Small pieces of metal in the engine oil of a car.
d) Different pigments from an extract of flower petals.
e) Butter from curd.
f) Oil from water.
g) Tea leaves from tea.
h) Iron pins from sand.
i) Wheat grains from husk.
j) Fine mud particles suspended in water.
Answer:

Mixture Separation technique
a) Sodium chloride from its solution in water Crystallization
b) Ammonium chloride from a mixture containing sodium chloride and ammonium chloride Sublimation
c) Small pieces of metal in the engine oil of a car Filtration
d) Different pigments from an extract of flower petals Chromatography
e) Butter from curd Centrifugation
f) Oil from water Separation funnel
g) Tea leaves from tea Filtration
h) Iron pins from sand Magnetism
i) Wheat grains from husk Winnowing
j) Fine mud particles suspended in water Sedimentation and decantation (or) Filtration using filter paper

AP Board 9th Class Physical Science Solutions Chapter 3 Is Matter Pure?

Question 2.
Write the steps you would use for making tea. Use the words given below and write the steps for making tea. (AS 7)
AP Board 9th Class Physical Science Solutions Chapter 3 Is Matter Pure 16
Answer:

  • Take a cup of milk (solvent) in a tea kettle.
  • Add one table spoon of sugar (solute), and one table spoon of tea powder (insoluble) to the solvent.
  • Heat the tea kettle on the stove.
  • The sugar (solute) dissolves in the milk (solvent) and the tea powder remains undissolved.
  • Now filter the solution so formed.
  • The filtrate is the tea (solution).
  • The residue remained in the sieve is the insoluble component of tea powder.

Question 3.
Explain the following giving examples. (AS 1)
a) Saturated solution
b) Pure substance
c) Colloid
d) Suspension
Answer:
a) Saturated solution :
When no more solute can be dissolved in the solution at a certain temperature, it is said to be a saturated solution.

In a saturated solution, equilibrium with the undissolved solute at a certain temperature.
AP Board 9th Class Physical Science Solutions Chapter 3 Is Matter Pure 1

Ex :

  1. Take 50 ml of water in a cup.
  2. Add one spoon of sugar to the cup and stir still it dissolves.
  3. Keep on adding sugar to the water in the cup and stir till no more sugar can be dissolved.
  4. The solution so formed is a saturated solution.

b) Pure substance :
A substance is pure i.e., homogeneous if the com-position doesn’t change, no matter which part of the substance we take for examination.
AP Board 9th Class Physical Science Solutions Chapter 3 Is Matter Pure 2
Ex :

  1. Take a small part of pure gold biscuit as a sample.
  2. The composition is found to be same throughout it.

c) Colloid :
Colloids are heterogeneous mixtures in which the particle size is too small to be seen with the naked eye, but is big enough to scatter light.
Ex : Milk, butter, cheese, cream, gel, etc.

d) Suspension :
Suspension is a heterogeneous mixture in which the solute particles didn’t dissolve and the particles are visible to naked eye.
Ex : Syrups, chalk powder mixed with water, etc.

AP Board 9th Class Physical Science Solutions Chapter 3 Is Matter Pure?

Question 4.
Classify each of the following as a homogeneous or heterogeneous mixture. Give reasons. (AS 1)
AP Board 9th Class Physical Science Solutions Chapter 3 Is Matter Pure 3
Answer:

Homogeneous mixtures Heterogeneous mixtures
Soda water Soil
Air Wood
Vinegar
Filtered tea
Reason : Components in the above mixtures are uniformly distributed and we cannot see the components separately. Reason : Components in the above mixtures are not uniformly distributed.

Question 5.
How would you confirm that a colourless liquid given to you is pure water? (AS 1)
Answer:

  • Observe the smell. We should not find any smell.
  • Observe with a naked eye we should not find any suspended particles or fumes or air bubbles.
  • Pass a beam of light. It should not scatter.
  • The temperature should be normal.
    Then the given colourless liquid is pure water.

Question 6.
Which of the following materials fall in the category of a “pure substance”? Give reasons. (AS 1)
a) Ice
b) Milk
c) Iron
d) Hydrochloric acid
e) Calcium oxide
f) Mercury
g) Brick
h) Wood
i) Air
Answer:

  • Except brick and wood remaining materials given in the list can be treated as pure substances.
  • Take any small part of ice, milk, iron, hydrochloric acid, calcium oxide, mercury and air and test for their components.
  • We find that the composition is same throughout them.

Question 7.
Identify the solutions among the following mixtures. (AS 1)
a) Soil
b) Sea water
c) Air
d) Coal
e) Soda water
Answer:
The solutions are : sea water, air and soda water.

Question 8.
Which of the following will show “Tyndall effect”? How can you demonstrate “Tyndall effect” in them? (AS 1, AS 3)
a) Salt solution
b) Milk
c) Copper sulphate solution
d) Starch solution
Answer:
Milk shows Tyndall effect.

Demonstration :

  1. Prepare the milk, copper sulphate, salt and starch solutions in different beakers.
  2. Allow a beam of light through each of them.
  3. The path of the light beam is clearly visible to us through milk.
  4. The path of the light beam is not visible through remaining.
  5. This experiment will be effective if it is performed in a dark room.

AP Board 9th Class Physical Science Solutions Chapter 3 Is Matter Pure?

Question 9.
Classify the following into elements, compounds and mixtures. (AS 1)
a) Sodium
b) Soil
c) Sugar solution
d) Silver
e) Calcium carbonate
f) Tin
g) Silicon
h) Coal
i) Air
j) Soap
k) Methane
l) Carbondioxide
m) Blood
Answer:

Elements Compounds Mixtures
Sodium Calcium carbonate Soil
Silver Coal Sugar solution
Tin Methane Air
Silicon Carbondioxide
Soap
Blood

Question 10.
Classify the following substances in the below given table. (AS 1)
AP Board 9th Class Physical Science Solutions Chapter 3 Is Matter Pure 15
Answer:

Solution Suspension Colloidal dispersion
Soda water Ink Fog
Fruit salad Nail polish Aerosol sprays
Black coffee Starch solution Boot polish
Air Brass Milk
Blood
Oil and water

Question 11.
Take a solution, a suspension, a colloidal dispersion in different beakers. Test whether each of these mixtures shows the Tyndall effect by focusing a light at the side of the container. (AS 3)
Answer:

  • Take sugar solution (solution), starch solution (suspension) and milk solution (colloidal dispersion) in three different beakers.
  • Focus a beam of light by torch or a laser beam at the side of each container and observe.
  • We can see that the path of beam of light is clearly visible through all the solutions.
  • Hence all the three solutions show ‘Tyndall effect”.

Question 12.
Draw the figures of arrangement of appatus for distillation and fractional distillation. What do you find the major difference in these apparatus? (AS 5)
Answer:
AP Board 9th Class Physical Science Solutions Chapter 3 Is Matter Pure 6 AP Board 9th Class Physical Science Solutions Chapter 3 Is Matter Pure 7
The main difference between these two apparatus is that a fractionating column is fitted in between the distillation flask and the condenser.

Question 13.
Determine the mass by mass percentage concentration of a 100 g salt solution which contains 20 g salt. (AS 1)
Answer:
Mass of salt = 20 g; Mass of salt solution = 100g
AP Board 9th Class Physical Science Solutions Chapter 3 Is Matter Pure 4

Question 14.
Calculate the concentration in terms of mass by volume percentage of the solution containing 2.5 g potassium chloride in 50 ml of potassium chloride (KCl) solution. (AS 1)
Answer:
Mass of potassium chloride = 2.5 g
Volume of potassium chloride solution = 50 ml
AP Board 9th Class Physical Science Solutions Chapter 3 Is Matter Pure 5

9th Class Physical Science 3rd Lesson Is Matter Pure? InText Questions and Answers

9th Class Physical Science Textbook Page No. 40

Question 1.
Can you give few more examples of this kind?
Answer:
Some more examples of homogeneous mixtures are sugar solution, lemon squash, fruit juices, syrups and tonics used in medicine, etc.

Question 2.
Can you prove this with an experiment?
Answer:

  • Take some thick milk in a test tube.
  • Pass a beam of light from torch or a laser light.
  • We cannot observe the path of light through the solution.

AP Board 9th Class Physical Science Solutions Chapter 3 Is Matter Pure?

Question 3.
If the solution is diluted, can the path of light be visible?
Answer:

  • Take some thick milk in a test tube.
  • Dilute it by adding some water.
  • Now pass a beam of light from torch or a laser light.
  • We cannot observe the path of light through the solution.

Question 4.
What would happen if you add a little more solute to a solvent?
Answer:
The solution becomes concentrated.

Question 5.
How do you determine the percentage of the solute present in a solution?
Answer:

  • Take 100 ml of water in a beaker.
  • Take 50 g. of sugar in a plate.
  • Add a spoon of sugar to water and stir it tell the sugar dissolve in water.
  • Go on adding sugar till you reach a situation that the sugar cannot be dissolved in water.
  • Now weigh the sugar remained in the plate.
  • Subtract thin weight from 50 g. The weight so obtained is dissolved in water.
  • Hence the maximum amount of solute present in 100 ml of solvent is the percentage of solute (solubility).

9th Class Physical Science Textbook Page No. 44

Question 6.
Did you ever observe this phenomenon in the cinema halls?
Answer:
In cinema halls when we observe the projector while the movie is running, we can observe the phenomenon of “Tyndall effect”. We can see the beams of light in which dust particles also observed.

9th Class Physical Science Textbook Page No. 46

Question 7.
Is the mixture heterogeneous? Give reasons.
Answer:
The mixture of ammonium chloride and salt is a heterogeneous mixture. Even though these two are white in colour their particles do not mix.

AP Board 9th Class Physical Science Solutions Chapter 3 Is Matter Pure?

Question 8.
How do we separate the salt and ammonium chloride?
Answer:
We can separate the salt and ammonium chloride by the method of sublimation.

9th Class Physical Science Textbook Page No. 49

Question 9.
Can you give any examples where we use fractional distillation technique?
Answer:
We use this technique in separating the components of crude oil i.e., petrol, naphthalene, kerosene, greese, etc.

9th Class Physical Science Textbook Page No. 38

Question 10.
How does a laundry dryer squeeze out water from wet clothes?
Answer:

  • The laundry dryer contains a cylindrical vessel with holes on its walls.
  • When wet clothes are dropped in it, it is rotated with high speed with the help of an electric motor.
  • Due to centrifugation, the water from the clothes reaches to the walls of the cylinder and comes out through the holes.
  • Hence the clothes are dried up.

9th Class Physical Science Textbook Page No. 40

Question 11.
a) “All the solutions are mixtures, but not all mixtures are solutions”. Discuss about the validity of the statement and give reasons to support your argument.
Answer:

  • You take any solution like salt solution, sugar solution, air, etc. all are homogeneous mixtures.
  • Consider a mixture of sand and iron fehlings. It is not homogeneous. Hence this is not a solution.

b) Usually we think of a solution as a liquid that contains either a solid, liquid or a gas dissolved in it. But, we can have solid solutions. Can you give some examples?
Answer:
Examples of solid solutions are :

  1. Steel used in constructions (a homogeneous mixture of iron and carbon).
  2. Brass (a homogeneous mixture of zinc and copper).

9th Class Physical Science Textbook Page No. 43

Question 12.
1) Have you ever observed carefully the syrup that you take for cough? Why do you shake it before consuming?
2) Is it a suspension or colloidal solution?
Answer:

  1. The syrup used for cough will be shook before consuming because it consists some undissolved particles settled down.
  2. Hence cough syrup is a suspension.

9th Class Physical Science Textbook Page No. 45

Question 13.
Is there any difference between a true solution and colloidal solution? If you find the differences, what are those differences?
Answer:
Differences between true solutions and colloidal solutions :
AP Board 9th Class Physical Science Solutions Chapter 3 Is Matter Pure 17

Question 14.
Why do we use different separation techniques for mixtures like grain and husk as well as ammonium chloride and salt though both of them are heterogeneous mixtures? What is the basis for choosing a separation technique to separate mixtures?
Answer:
The basis for choosing a separation technique to separate mixtures is the property of a component in the mixture i.e., solubility in water, evaporation, appearance, etc.

9th Class Physical Science Textbook Page No. 47

Question 15.
Is it possible to find out adulteration of kerosene in petrol with this technique?
Answer:
The adulteration of kerosene in petrol can be found by using density meter.

9th Class Physical Science Textbook Page No. 50

Question 16.
a) Arrange the gases present in air in increas you observe?
Answer:

Gas B.P
Helium 268.93°C
Hydrogen 252.9°C
Neon 246.08°C
Nitrogen 195.8°C
Argon 185.8°C
Oxygen 183°C
Methane 164°C
Krypton 153.22°C
Xenon 108.12°C
Carbondioxide 78°C

b) Which gas forms the liquid first as the air is cooled?
Answer:
Oxygen forms the liquid first as the air is cooled.

9th Class Physical Science 3rd Lesson Is Matter Pure? Activities

Activity – 1

Question 1.
How can we separate cream from milk?
Answer:
AP Board 9th Class Physical Science Solutions Chapter 3 Is Matter Pure 8

  • Take some milk in a vessel.
  • Spin it with a milk churner for some time.
  • After some time you observe, separation of a paste like solid out of the milk.
  • The paste like solid is called cream.

Activity – 2

Question 2.
Explain a demonstration to identify homogeneous and heterogeneous mixtures.
Answer:

  • Take two test tubes.
  • Now add one tea spoon of salt to both the test tubes.
  • Fill one test tube with water and another with kerosene and stir them.
  • In the first test tube (water), the salt dissolves completely.
  • This is a homogeneous mixture.
  • In the second test tube (kerosene), the salt is not dissolved.
  • This is a heterogeneous mixture.

Activity – 3

Question 3.
Describe an activity to prepare saturated and unsaturated solutions.
Answer:
Preparation of saturated solution :
AP Board 9th Class Physical Science Solutions Chapter 3 Is Matter Pure 1

  1. When no more solute can be dissolved in the solution at a certain temperature, it is said to be a saturated solution.
  2. Take 50 ml of water in an empty cup.
  3. Add one spoon of sugar to the water in the cup.
  4. Stir the water until it dissolves.
  5. Keep on adding sugar to the cup and stir till no more sugar can be dissolved in it.
  6. Thus formed solution is called saturated solution.
  7. In a saturated solution, equilibrium with the undissolved solute at a certain temperature.

Preparation of unsaturated solution :
AP Board 9th Class Physical Science Solutions Chapter 3 Is Matter Pure 9

  1. If the amount of solute present in a solution is less than that in the saturated solution, is called an unsaturated solution.
  2. Now take the solution prepared by you into a beaker.
  3. Heat that solution slowly by 5 to 6°C above the room temperature.
  4. The undissolved solute dissolves.
  5. Add some more sugar to this solution.
  6. You notice that more sugar dissolves in it easily when it is heated.
  7. Thus we prepared an unsaturated solution.

Activity – 4

Question 4.
What are the factors affecting the rate of dissolving ? How do you prove them?
Answer:
Factors affecting the rate of dissolving are :

  1. Temperature of the solvent.
  2. Size of the solute particles.
  3. Stirring the solution.

Proof:

  1. Take three glass beakers and fill each of them with 100 ml of water.
  2. Add two spoons of salt to each beaker.
  3. Place the first beaker undisturbed.
  4. Stir the contents of the second beaker.
  5. Heat gently the third beaker.
  6. In all the cases, the salt dissolves but the time taken to dissolve is different.
  7. When the beaker is heated, the salt dissolved quickly.
  8. When we stir the contents, the salt dissolved but slower than heating.
  9. When we observe the undisturbed beaker, the salt dissolves but at the slowest rate.
  10. This shows that the temperature of the solvent, size of the solute particles, stirring of contents are the factors affecting the rate of dissolving.

Activity – 5

Question 5.
Describe an experiment to identify suspensions and colloids.
Answer:

  • Take some chalk powder in a test tube.
  • Take a few drops of milk in another test tube.
  • Add water to these samples and stir with a glass rod.
  • Now do the following steps and write your observations in the table given.

Step 1 :
Direct a beam of light from a torch or a laser beam on the test tubes. Observe the path of the light through the solutions.

Step 2 :
1) Leave the mixture undisturbed for some time.
2) See whether the solute settles down after some time.

Step 3 :
Filter the mixtures and observe any residue found on the filter paper.
Now read your observations :
AP Board 9th Class Physical Science Solutions Chapter 3 Is Matter Pure 10

Observations :

  1. In the chalk mixture, the particles of chalk settled at the bottom of the test tube and on filtration, we can observe a residue on the filter paper.
  2. Hence the chalk mixture is a suspension.
  3. In the milk mixture, the particles of milk are uniformly spread throughout the mixture and no residue is found on the filter paper.
  4. Hence milk mixture is a colloidal solution.

Activity – 6

Question 6.
Describe an example for the separation of mixtures by sublimation.
Describe a method of separating ammonium chloride from the mixture of ammonium chloride and common salt.
Answer:
Aim :
To separate ammonium chlo-ride from the mixture of ammonium chloride and common salt.

Materials required :
China dish, funnel, cotton, ammonium chloride, common salt and stove.
AP Board 9th Class Physical Science Solutions Chapter 3 Is Matter Pure 11
Procedure:

  1. Take one table spoon of ammo-nium chloride and one table spoon of common salt and mix them.
  2. Take the mixture in a China dish.
  3. Take a glass funnel.
  4. Plug the mouth of the funnel with cotton.
  5. Invert the funnel over the dish.
  6. Heat the dish on the stove and observe the walls of the funnel.

Observations :
Initially we find vapours of ammonium chloride and then solidified ammonium chloride on the walls of the funnel.

Activity – 7

Question 7.
Describe a method to separate the dye present in ink.
(or)
Describe an example for the separation of a mixture by the process of evaporation.
Answer:
Aim :
To separate the dye present in ink by the process of evaporation.

Materials required :
Beaker, watch glass, water, ink and stove.
AP Board 9th Class Physical Science Solutions Chapter 3 Is Matter Pure 12

Procedure :

  1. Take a beaker and fill it to half its volume with water.
  2. Keep 3, glass on the mouth of a beaker.
  3. Put few drops of ink on the watch glass.
  4. Heat the beaker and observe the watch glass.

Observations:

  1. We observe some fumes coming from the watch glass.
  2. Continue heating till you do not observe any further change on the watch glass.
  3. A small residue will be remained on the watch glass.

Inference :

  1. We know that ink is a mixture of a dye in water.
  2. The residue remained on the watch glass is the dye present in the ink.

Lab Activity

Question 8.
Describe paper chromatography activity to observe the colours present in a marker ink.
(OR)
How can you perform chromatography activity in your laboratory.
Answer:
Aim :
Separating the components of ink using paper chromatography.

Materials required :
Beaker, rectangular shaped filter papers, black marker (non-permanent), water, pencil and cello tape.
AP Board 9th Class Physical Science Solutions Chapter 3 Is Matter Pure 13
Procedure:

  1. Draw a thick line just above the bottom of the filter paper using the marker.
  2. Pour some water into the beaker.
  3. Hang the paper strip with help of a pencil and tape in such a way that it should just touch the surface of water.
  4. Make sure that the ink line or mark does not touch the water.
  5. Allow the water to move up the paper for 5 minutes and then remove the strip from water.
  6. Let it dry.
  7. Repeat the process with green marker, a permanent marker, etc.

Observations :

  1. When black marker is used, we observe different colours like red, green, violet, black, etc. on the filter paper after drying.
  2. When green marker is used, we observe yellow, blue, green colours on the filter paper.
  3. When permanent marker is used, we cannot find any change in the mark.

Activity – 8

Question 9.
How do you separate water and kerosene from the mixture of kerosene and water?
Answer:
Aim :
To separate water and kerosene from the mixture of kerosene and water.

Materials required :
Kerosene, water, separating funnel, beakers.
AP Board 9th Class Physical Science Solutions Chapter 3 Is Matter Pure 14
Procedure:

  1. Pour the mixture of kerosene and water in a separating funnel.
  2. Let it stand undisturbed for some time, so that the layers of oil and water are formed.
  3. Open the stopcock of the separating funnel and pour out the lower layer of water carefully.
  4. Close the stopcock of the separating funnel as the oil reaches the stop cock.

Principle involved :
The immiscible liquids separate out into layers depending on their densities.

Activity – 9

Question 10.
Explain the method of separation of two miscible liquids by distillation.
Answer:
Aim :
To separate two miscible liquids (water and acetone) by distillation.

Materials required :
Stand, distillation flask, thermometer, condenser, beaker, acetone and water, one holed rubber cork.
AP Board 9th Class Physical Science Solutions Chapter 3 Is Matter Pure 6
Procedure:

  1. Take a mixture of acetone and water in a distillation flask.
  2. Fit it with a thermometer and clamp it to stand.
  3. Attach the condenser of the flask on one side.
  4. On the other side of the condenser keep a beaker to collect distillate.
  5. Heat the mixture slowly.
  6. Keep a close watch on the thermometer.
  7. The acetone vapourizes and condenses in the condenser.
  8. The acetone can be collected from the condenser outlet.
  9. Water remains in the distillation flask.
  10. The separation technique used above is called distillation.

Activity – 10

Question 11.
How do you separate copper metal from the mixture of copper sulphate and aluminium?
Answer:

  • Take a concentrated solution of copper sulphate into a beaker.
  • Drop an aluminium foil in the beaker.
  • After some time, we observe a layer of copper deposited on the aluminium foil.
  • The solution becomes colourless.
  • A chemical reaction takes place among the copper ions present in the solution with aluminium and copper metal is separated.

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