Page No 24: - Chapter 2 Is Matter Around Is Pure class 9 ncert solutions Science - SaraNextGen [2024-2025]

Updated By SaraNextGen

On April 24, 2024, 11:35 AM

Question 1:

How will you separate a mixture containing kerosene and petrol (difference in their boiling points is more than 25°C), which are miscible with each other?

Answer:

A mixture of two miscible liquids having a difference in their boiling points more than 25°C can be separated by the method of distillation. Thus, kerosene and petrol can be separated by distillation.

In this method, the mixture of kerosene and petrol is taken in a distillation flask with a thermometer fitted in it. We also need a beaker, a water condenser, and a Bunsen burner. The apparatus is arranged as shown in the above figure. Then, the mixture is heated slowly. The thermometer should be watched simultaneously. Kerosene will vaporize and condense in the water condenser. The condensed kerosene is collected from the condenser outlet, whereas petrol is left behind in the distillation flask.

Question 1:

Classify the following as chemical or physical changes:

• Cutting of trees

• Melting of butter in a pan

• Rusting of almirah

• Boiling of water to form steam

• Passing of electric current through water, and water breaking down into hydrogen and oxygen gas

• Dissolving common salt in water

• Making a fruit salad with raw fruits

• Burning of paper and wood

Answer:

• Cutting of trees → Physical change

• Melting of butter in a pan → Physical change

• Rusting of almirah → Chemical change

• Boiling of water to form steam → Physical change

• Passing of electric current through water, and water breaking down into hydrogen and oxygen gas → Chemical change

• Dissolving common salt in water → Physical change

• Making a fruit salad with raw fruits → Physical change

• Burning of paper and wood → Chemical change

Question 2:

Name the technique to separate

(i) butter from curd

(ii) salt from sea-water

(iii) camphor from salt

Answer:

(i) Butter can be separated from curd by centrifugation.

(ii) Salt can be separated from sea-water by evaporation.

(iii) Camphor can be separated from salt by sublimation.

Question 2:

Try segregating the things around you as pure substances or mixtures.

Answer:

Pure substance: Water, salt, sugar

Mixture: Saltwater, soil, wood, air, cold drink, rubber, sponge, fog, milk, butter, clothes, food

Question 3:

What type of mixtures is separated by the technique of crystallization?

Answer:

By the technique of crystallization, pure solids are separated from impurities. For example, salt obtained from the sea is separated from impurities; crystals of alum (Phitkari) are separated from impure samples.