NCERT Class 9 Science Solutions: Chapter 2 – Is Matter Around Us Pure Part 2

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Question 1:

Q. Classify the following as chemical of physical changes:

Pure Physical Change and Chemical Change for Matter Around

Physical Change and Chemical Change

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(i) Cutting of trees

A. Cutting of trees → Physical change

(ii) Melting of butter in a pan

A. Melting of butter in a pan → Physical change

(iii) Rusting of almirah

A. Rusting of almirah → Chemical change

(iv) Boiling of water to from steam

A. Boiling of water to form steam → Physical change

(v) Passing of electric current through water, and water breaking down into hydrogen and oxygen gas

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

(vi) Dissolving common salt in water

A. Dissolving common salt in water → Physical change

(vii) Making a fruit salad with raw fruits

A. Making a fruit salad with raw fruits → Physical change

(viii) Burning of paper and wood

A. Burning of paper and wood → Chemical change

Question 2:

Q. Try segregating the things around you as pure substance or mixtures.

A. Pure substance: Water, salt, sugar

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

Question 1:

Q. Which separation techniques will you apply for the separation of the following?

(a) Sodium chloride from a mixture containing sodium chloride and ammonium chloride.

A. Sodium chloride from its solution in water → Evaporation

(b) Ammonium chloride from a mixture containing sodium chloride and ammonium chloride.

A. Ammonium chloride from a mixture containing sodium chloride and ammonium chloride → Sublimation

(c) Small pieces of metal in the engine oil of car.

A. Small pieces of metal in the engine oil of a car → Centrifugation or filtration or decantation

(d) Different pigments from an extract of flower petals.

A. Different pigments from an extract of flower petals → Chromatography

(e) Butter from curd.

A. Butter from curd → Centrifugation

(f) Oil from water.

A. Oil from water → Using separating funnel

(g) Tea leaves from tea.

A. Tea leaves from tea → Filtration

(h) Iron pins from sand.

A. Iron pins from sand → Magnetic separation

(i) Wheat grains from husk.

A. Wheat grains from husk → Winnowing

(j) Fine mud particles suspended in water.

A. Fine mud particles suspended in water → Centrifugation

Question 2:

Q. Write the step you would use for making tea. Use the words: solution, solvent, solute, dissolve, soluble, insoluble, filtrate and residue.

A. First, water is taken as a solvent in saucer pan. This water (solvent) is allowed to boil. During heating, milk and tea leaves are added to the solvent as solutes. They form a solution. Then, the solution poured through a strainer. The insoluble part of the solution remains on the strainer as residue. Sugar is added to the filtrate, which dissolves in the filtrate. The resulting solution is the required tea.