Question

Classify the following into physical and chemical change.
Rusting of iron

Answer 1

• Physical change: A change in which only the physical properties of any substance get changed is called a physical change.
• During a physical change, no new substance is formed.
• Chemical change: A change in which the composition and chemical properties of the substance get changed is called a chemical change.
• During a chemical change, one or more new substances are formed.
• Rusting of iron is a chemical change, when the iron is exposed to air and moisture, it gets covered with rust. The formation of rust on the surface of iron is called rusting of iron.
• Here the composition and properties of rust are different from iron.
• Rust cannot be converted back to iron by simple physical methods.

$4\mathrm{Fe}\left(\mathrm{s}\right)+3{\mathrm{O}}_2\left(\mathrm{g}\right)+2{\mathrm{xH}}_2\mathrm{O}\left(\mathrm{l}\right)\to 2{\mathrm{Fe}}_2{\mathrm{O}}_3.{\mathrm{xH}}_2\mathrm{O}\left(\mathrm{s}\right)$

• Hence, rusting of iron is a chemical change.