Question

(A): A jar of water was boiled. After some time, steam was seen coming out of the container.
(i) What is the process called?
(ii) What kind of change is this?

(B): Justify the characteristics of physical change with the help of example.

Answer 1

(A) (i) Evaporation is the process of loss of water as water vapour from the surface of water.
(ii) Evaporation is a physical change. When the water vapour is allowed to be cooled, its physical state changes back to liquid form.

(B): No new substances are formed during physical change.
Example-When ice is heated, it melts and turns into water. When the water is heated further, it turns into steam. The steam condenses and becomes water when it cools. The water forms into ice as it cools further. Ice, water, and steam molecules, always have two hydrogen atoms and one oxygen atom. As a result, we can conclude that no new substances are formed.

Physical changes can be generally reversed.
Example- When the wax is heated, it turns into a liquid. However, when liquid wax cools, it solidifies.

There is no change in weight during physical change.
Example- Make a salt solution by dissolving 20g of salt in water, it will end up with 20g of salt after the water evaporates.