Combustion, oxidation and putrefaction are chemical changes.


Some materials can burn.
When they burn, its atoms react with the oxygen.
As a result, they transform into new substances (smoke and ash).
This process is called combustion.


Rusting is a chemical change. This process is called oxidation.
Oxygen and water are needed for rusting to occur.
Iron and steel rust when they come into contact with them.


When organic matter decomposes, putrefaction occurs.
Putrefaction is a chemical change.
It happens to fresh fruit when you leave it for long time.
The food softens, changes colour and smells bad.