5.3.1 Rusting

What is Rusting?

It means iron getting a brown coating when left in moist air.

The brown coating is called rust .

Examples

• An old bicycle handle turning brown.
• Iron gates becoming reddish-brown in the rainy season.
• Old iron nails getting a flaky brown layer.
• Iron tools left in a damp place.

What happens during rusting

• Iron is exposed to moist air for a long time.
• A brown layer slowly forms on its surface.
• This brown layer is a new substance called iron oxide .
• Since a new substance forms, rusting is a chemical change .

Why Does Rusting Matter?

Rust is harmful for most things made of iron.

Problems caused by rusting

• Rust weakens iron objects.
• Many useful items get spoilt:
  • Tools become weak.
  • Gates rust through.
  • Vehicle bodies become unsafe.
  • Bridges lose strength.
• So rusting is an undesirable chemical change.