Which of the following is a chemical change?

Rusting of iron

The correct answer is Option (2) → Rusting of iron

Rusting of iron is a chemical change because a new substance (iron oxide) is formed through a chemical reaction between iron, water, and oxygen. It is irreversible under normal conditions.

• Dissolving of salt in water: Physical change – no new substance is formed, and the process is reversible.

• Boiling of water: Physical change – water changes from liquid to gas, but remains H₂O.

• Melting of ice: Physical change – ice becomes water, still H₂O.