Question

Why is rusting of iron termed as a chemical change?

• A. It is a temporary change.
• B. A new substance is formed.
• C. The original substance can be recovered.
• D. The shape of iron changes.

Answer 1

The correct option is B

A new substance is formed.

Iron reacts chemically with oxygen and water vapour present in the air and thus rust formation takes place. Rust is iron(ii) oxide, a new substance formed out of the reaction. The colour of the surface of the iron also changes in this reaction. The reaction is as follows:

$4\text{Fe}\text{(s)}+2{\text{O}}_2\text{(g)}\to \text{2}{\text{Fe}}_2{\text{O}}_3\text{(s)}$

Hence, rusting of iron is a chemical change.