Question

Classify the following change as chemical and physical change:

Boiling of water to form steam

Answer 1

Chemical change: A change in which one or more new substances are formed and there is a change in the chemical composition of the substance undergoing the change.

Physical change: A change in which no new substance is formed and there is no change in the chemical composition of the substance undergoing the change.

Boiling of Water $\left({\mathrm{H}}_2\mathrm{O}\right)$ to form steam is a physical change.

• This is because the physical state of water changes from liquid to gas without any change in its composition.
• No new chemical substance is being formed during the process.
• It is a temporary and reversible change as water can be brought back into its liquid form from steam on cooling.