1. Oxidation and Reduction
When a substance gains oxygen
Magnesium +
oxygen
Magnesium oxide
It said to have been OXIDISED
When a substance loses oxygen
Magnesium oxide
Magnesium +
oxygen
It said to have been REDUCED

2. The process of gaining oxygen is said to be OXIDATION
The process of losing oxygen is said to be REDUCTION

3. LEAD OXIDE + CARBON LEAD + CARBON DIOXIDE
Is reduced
Is oxidised
HYDROGEN + COPPER OXIDE COPPER + WATER
Is oxidised
Is reduced
METHANE + SILVER OXIDE SILVER + WATER CARBON DIOXIDE
Is oxidised
Is reduced

4. The oxidising agent gives oxygen to another substance.
E.g.
magnesium + oxygen magnesium oxide
The oxidising agent is oxygen.

5. The reducing agent takes oxygen away from another substance. E.g.
Hydrogen is the reducing agent
HYDROGEN + COPPER OXIDE COPPER + WATER