Chapter 6: Changes Around Us

Ans: Yes, the water can be turned into water vapour. Condensation can be used to make this reversible change. The water vapour will be condensed or cooled off to form water.

Ans: Water vapour into water is a reversible change. The process here is evaporation. When then water vapours are condensed to form water, it can be heated or evaporated to form water vapour again.

Ans: Ice into water is also a reversible change. Once the ice is melted into water, it can be gained back by freezing. The melted water will again form ice.

Ans: Changing of curd into milk is an irreversible change. The transformation of milk into curd is a chemical process that is difficult to reverse. So once the milk is converted into curd, it cannot be changed into its original state.

Ans: The following changes are irreversible-

(d) Baking cake in an oven,

(f) Making biogas from cow dung.

(g) Burning of a candle.

Ans: No, Boojho will not be able to recreate the dove from the shattered Plaster of Paris parts because the process is irreversible. The POP loses its properties once mixed with water and converted into something and dried.

Ans: Recycling paper is the same as tearing paper. As on recycling properties of paper change, like the texture, colour, quality etc. therefore, it is an irreversible change.