Class 8 Science Chapter 2 Practice Question Answers - Is Matter Around Us Pure?

Objective Type Questions :

1. Which of the following is not a compound -

(A) Common salt (B) Water (C) Iron fillings (D) Copper sulphate

2. Which of the following is not a mixture -

(A) Soil (B) Air (C) Steam (D) Milk

3. Brass contains -

(A) Gold and copper (B) Copper and zinc (C) Zinc and silver (D) Copper and silver

4. Which of the following is not a chemical change-

(A) Electrolysis of water

(B) Boiling of water

(C) Digestion of food

(D) Burning of magnesium ribbon in oxygen to form magnesium oxide.

5. Which of the following is a liquid metal-

(A) Copper (B) Mercury (C) Bromine (D) Silver

6. Which of the following is not a pure substance -

(A) Mercury (B) Sugar (C) Blood (D) Salt

7. Which of the following can be classified as a 'Substance' -

(A) Milk (B) Sea-water (C) Ice (D) Cast iron

8. Which of the following gives a true solution in water-

(A) Starch (B) Sugar (C) Chalk powder (D) Egg albumin

9. Which of the following statements is not correct-

(A) A compound is a pure substance

(B) Compound is homogeneous in nature

(C) Compound always contains two or more elements

(D) Compound can be separated into constituent elements by some physical process.

10. Which of the following statements is not true -

(A) True solutions are homogeneous in nature

(B) Suspensions are heterogeneous in nature

(C) Solute particles in a colloidal solution can be separated by filtration

(D) True solutions are transparent to light

11. Which of the following is the second most abundant metal in the earth's crust ?

(A) Copper (B) Aluminium (C) Iron (D) Zinc

12. Which of the following will show Tyndall effect-

(A) Starch solution (B) Sodium chloride solution

(C) Copper sulphate solution (D) Sugar solution

13. When a beam of light is passed through a true solution, it gets-

(A) Reflected (B) Absorbed (C) Scattered (D) Path of light does not visible

14. Camphor can be purified by-

(A) Distillation (B) Filtration (C) Sedimentation (D) Sublimation

15. Carbon burns in oxygen to form carbon dioxide. The properties of carbon dioxide are-

(A) Similar to oxygen (B) Similar to carbon

(C) Totally different from both carbon and oxygen (D) Much similar to both carbon and oxygen

16. A mixture of common salt and water can be separated by-

(A) Sublimation (B) Evaporation (C) Separating funnel (D) Filtration

17. The process of cooling a hot, concentrated solution of a substance to obtain crystal is called -

(A) Fractional distillation (B) Distillation (C) Crystallisation (D) Chromatography

18. A solution in which more quantity of solute can be dissolved without raising its temperature is called -

(A) Unsaturated solution (B) Saturated solution

(C) Super saturated solution (D) Concentrate solution

19. Colloidal particles can be normally seen by-

(A) Ordinary microscope (B) Naked eye

(C) Electron microscope (D) Telescope

20. A mixture of alcohol and water can be separated by -

(A) Separating funnel (B) Fractional distillation (C) Distillation (D) Crystallisation

Fill in the blanks :

1. Compound is a ............substance.

2. Wood is a .............

3. Electrolysis of water is a ............change.

4. Digestion of food is a............change.

5. ............is a metal which exists as liquid.

6. Gases can be separated from air by............method.

7. ............show tyndall effect.

8. Brass is a mixture of ............and ...............

9. 10% by mass of a solution means............g of solute are present in 50gm of solution.

10. Air is a.............

 EXERCISE # 3

Write T for true and F for false statement :

1. Steam is a compound.

2. Mercury is a liquid non-metal.

3. Mass percentage of a solution containing 10 g of solute in 100g of water is 10%.

4. Mixture of salt and ammonium chloride can be separated by cyrstallisaion process.

5. Constituents of a mixture can be separated by physical methods.

6. Milk, coffee and brass are example of mixtures.

7. Digestion of food is a physical change.

8. Solutions cannot be separated by the process of filtration.

9. Fog is an example of liquid dispersed in gas.

Very Short Answer Questions :

1. Is steam an element, a compound or a mixture ?

2. Name the two main steps used for separation of gases from air.

3. By which method will you separate a mixture of oil and water ?

4. Arrange true solution, suspension and colloid in the decreasing order of size of the particles.

5. What type of mixture are separated by the technique of crystallisation.

6. Name of the technique to separate.

(i) butter from curd

(ii) salt from sea water

(iii) camphor from salt

7. How would you confirm that a colourless liquid given to you is pure water ?

8. Classify each of the following as a homogeneous or heterogenous mixture. Soda water, wood, air, vinegar, Filtered tea.

9. Identify the solutions among the following mixtures.

(a) soil

(b) sea water

(c) air

(d) coal

(e) soda water

10. What is meant by a pure substance ?

EXERCISE # 4

Long Type Questions :

1. What is a mixture ? Name two types of mixtures and give two examples of each.

2. What is a solution ? Give its three properties.

3. What is a suspension ? Give its three properties.

4. Explain the method to separate cream from milk.

5. How can we obtain coloured component from blue/ black ink? explain.

6. Explain the method to separate a mixture of salt and ammonium chloride.

7. Discuss the method to separate a mixture of :

(i) two miscible liquids,

(ii) two immisicible liquids.

8. What are physical and chemical changes ? Give two examples of each.

9. Define element, compound and mixture. Give two examples of each.

10. Give differences between compounds and mixtures

11. Write a brief notes on :

(i) Tyndall effect (ii) Solubility

12. What type of mixtures are separated by the technique of cyrstallisation ? Explain one.

13. A mixture contains water, kerosene and sand, How will you separate this mixture ?

14. Explain the differences between :

(i) Homogeneous mixture and heterogeneous mixture

(ii) Physical and chemical change

15. Define the following terms

(i) Saturated solution

(ii) Solvent

ANSWER KEY

 l Objective type questions

1. C 2. C 3. B 4. B 5. B 6. C 7. C 8. B 9. D 10. C

11. C 12. A 13. D 14. D 15. C 16. B 17. C 18. A 19. C 20. B

True or False :

1. F 2. F 3. F 4. F 5. T 6. T 7. F 8. T 9. T

 Fill in the blanks

1. Pure 2. Mixture 3. Chemical

4. Chemical 5. Mercury 6. Fractional disttillation

7. Colloids 8. Copper and zinc 9. 5g

10. Mixture