Combustion, oxidation and putrefaction are chemical changes.

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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.

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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.

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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.

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