Question

which one of the change given below cannot be reversed?
(1) formation of steam from water
(2) Burning of coal.
(3) Dissolving salt in water
(4) Melting of wax​

Answer 1

Answer:

2) Burning of coal

When coal is burnt, carbon reacts with the oxygen present in the air and produces carbon dioxide. This is called combustion.

Combustion is a chemical reaction.

There is a change in chemical composition and this reaction cannot be reversed as carbon dioxide cannot be converted into coal again. Hence, the burning of coal is a chemical an irreversible change.

Answer 2

which one of the change given below cannot be reversed?

(1) formation of steam from water.

(2) Burning of coal.

(3) Dissolving salt in water.

(4) Melting of wax​.

2) Burning of coal ,

When coal is burnt, carbon reacts with the oxygen present in the air and produces carbon dioxide. This is called combustion.

Combustion is a chemical reaction.

There is a change in chemical composition and this reaction cannot be reversed as carbon dioxide cannot be converted into coal again.

Hence, the burning of coal is a chemical an irreversible change.