Is matter around us pure Worksheet-5

Is matter around us pure Worksheet-5

1. Kerosene and Petrol are miscible liquids. The difference between their boiling points is more than 25°C. The two liquids can be separated from each other by _____.

A. Simple distillation                   B. Steam distillation

C. Fractional distillation             D. Any of these

2. Butter is separated from curd by _____.

A. Distillation                                B. Evaporation

C. Centrifugation                          D. Sublimation

3. Salt from sea water is obtained by _____.

A. Evaporation

B. Sublimation

C. Distillation

4. Camphor is separated from salt by _____.

A. Sublimation

B. Distillation

C. Crystallisation

5. Which of the following materials are pure substances?

(a) Ice (b) Milk (c) Iron (d) Hydrochloric acid (e) Calcium oxide (f) Mercury (g) Brick (h) Wood (i) Air.

A. (a), (c), (e), (f)                          B. (a), (d), (e), (f), (c)

C. (a), (h), (d), (f)                         D. (a), (d), (g), (f), (c)

6. Which of the following will show "Tyndall effect" ?

(a) Sodium chloride solution (b) Milk (c) Copper sulphate solution(d) Starch sol

A. (a), (c), (d)                                B. (b), (d)

C. (a), (b), (d)                                D. (c), (d)

7. How can a saturated solution be made unsaturated?

A. By heating the solution

B. By cooling the solution

C. By increasing the amount of solute

D. By centrifugation of the solution

8. Why the dispersed phase particles do not combine with one another in a colloidal solution?

A. Particles of dispersed phase combine with the particles of dispersion medium so they do not combine with each other.

B. Dispersion medium forms a layer between the particles of dispersed phase so they do not combine with one another

C. Due to the presence of similar charge on the dispersed phase particles they repel each other

Answer Key:

1. A

Explanation: By simple distillation. Vapours of the liquid which has low boiling point will be formed first and collected. The liquid having higher boiling point will remain in the vessel.

2. C

Explanation: Butter is separated from curd by centrifugation.

3. A

Explanation: Salt from sea water is obtained by evaporation.

4. A

Explanation: Camphor sublimes hence camphor is separated from salt by sublimation.

5. A

Explanation: Pure substances in the given list of materials are :

(a) Ice (compound) (c) Iron (element) (e) Calcium oxide (compound) (f) Mercury (element).

Both milk and hydrochloric acid are homogeneous mixtures.

Hydrochloric acid is formed by passing the vapours of hydrogen chloride gas through water.

6. B

Explanation: Milk and starch are colloidal solution hence they show Tyndall effect.

Sodium chloride solution and copper sulphate solution are true solutions hence they do not show Tyndall effect.

7. A

Explanation: A saturated solution can be made unsaturated by increasing the temperature of solution by heating it or by increasing the amount of solvent in the solution i.e. diluting it.

8. C

Explanation: Similar charge (positive / negative) is present on the particles of dispersed phase. For example iron sol particles have positive charge due to which they repel each other.