NCERT Class – 9 Science Solution: Chapter 2 is Matter Around Us Pure-Part 4 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Question: 12

Salt can be recovered from its solution by evaporation. Suggest some other technique for the same?




Question: 13

The ‘sea-water’ can be classified as a homogeneous as well as heterogeneous mixture. Comment.


  • Homogeneous — mixture of salts and water only
  • Heterogeneous — contains salts, water, mud, decayed plant etc.
Homogeneous and Heterogeneous Mixture

Question: 14

While diluting a solution of salt in water, a student by mistake added acetone (boiling point What technique can be employed to get back the acetone? Justify your choice.


Distillation, since acetone is more volatile it will separate out first.

Question: 15

What would you observe when

  1. A saturated solution of potassium chloride prepared at is allowed to cool to room temperature.
  2. An aqueous sugar solution is heated to dryness.
  3. A mixture of iron filings and sulphur powder is heated strongly.


  1. Solid potassium chloride will separate out.
  2. Initially the water will evaporate and then sugar will get charred.
  3. Iron sulphide will be formed.

Question: 16

Explain why particles of a colloidal solution do not settle down when left undisturbed, while in the case of a suspension they do.


  • Particle size in a suspension is larger than those in a colloidal solution.
  • Also molecular interaction in a suspension is not strong enough to keep the particles suspended and hence they settle down.

Question: 17

Smoke and fog both are aerosols. In what way are they different?


  • Both fog and smoke have gas as the dispersion medium.
  • The only difference is that the dispersed phase in fog is liquid and in smoke it is a solid.

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