* Chemical Change: Involves the formation of new substances with different properties.

* Physical Change: Alters the form or appearance of a substance but doesn't change its chemical composition.

What happens when iron rusts:

* Reactants: Iron (Fe), oxygen (O2) from the air, and water (H2O)

* Products: Iron oxide (Fe2O3), a reddish-brown compound that's different from the original iron.

Key Indicators of a Chemical Change:

* Formation of a new substance: Rust is a completely different substance from iron.

* Color change: Iron turns reddish-brown.

* Change in chemical composition: The atoms of iron combine with oxygen to form iron oxide.

Let me know if you'd like more details about the chemical reaction involved in rusting!