Which of the following materials fall in the category of a “pure substance”? Give reasons.

(a) Ice (b) Milk

(c) Iron (d) Hydrochloric acid

(e) Calcium oxide (f) Mercury

(g) Brick (h) Wood

(i) Air

(a) Pure substance

Ice is a pure substance as it only contains water particles in it.

(b) Impure substance

Milk is an impure substance as it is a mixture of carbohydrates, calcium etc.

(c) Pure substance

Iron is a pure substance as it contains only the iron particles in it

(d) Pure substance

Hydrochloric acid is a pure substance as it contains only the hydrogen chloride particles.

(e) Pure substance

Calcium oxide is a pure substance as it contains only the Calcium oxide particles in it.

(f) Pure substance

The mercury (hydrargyrum) is a pure substance as it contains only the mercury particles in it.

(g) Impure substance

Brick is made up of the mixture of clay and shale due to this it is an impure substance.

(g) Impure substance

Since the composition of wood varies from plant to plant thus wood is an impure substance.

(i) Impure substance

Air contains various other gases mixed with it such as oxygen, nitrogen etc. due to this air is impure.