Question

(ii) How can we identify a physical change as either reversible or irreversible? Use examples to support your answer.​

Answer 1

Answer:

Physical changes are changes that occur in the physical properties of the substance, like shape, size, and nature. Physical changes may or may not be reversible changes. Like, turning of water into ice is an example of reversible changes but growth in height is an irreversible change.

Chemical changes are changes that occur in the chemical properties of the substance like its flammability, radioactivity, etc. All chemical changes are irreversible changes. Once the chemical properties of a substance are changed, it becomes another substance. Thus, it cannot return to its original state.

Explanation:

Reversible Chanhes EX:

Melting: Melting is when solid converts into a liquid after heating. Example of melting is turning of ice into water.

Freezing: Freezing is when a liquid converts into a solid. Example of freezing is turning of water into ice.

Boiling: Boiling is when a liquid converts into a gas. Example of boiling is turning water into water vapour.

Irreversible changes EX:

Burning: When we burn a piece of paper or wood, it turns to ash and smoke. We cannot obtain paper and wood from the ash again.

Cooking: We use heat for cooking, right? Once we cook our eggs, we cannot uncook them. Therefore, cooking is an irreversible change.

Rusting of iron: You must have seen rusting of iron. When water vapour (humidity) comes in contact with the iron, they react. Therefore, iron rusts and once this happens, we cannot reverse it.