Oxidation and Reduction

This lesson covers oxidation and reduction (redox reactions) as specified in the AQA GCSE Chemistry syllabus (4.4.1). You need to understand what oxidation and reduction mean in terms of oxygen transfer and electron transfer, identify which substances are oxidised and reduced in a reaction, and recognise oxidising and reducing agents. These concepts are fundamental to understanding chemical changes, extraction of metals, and electrochemistry.

---

Definitions of Oxidation and Reduction

Oxidation and reduction always occur together — they are two halves of the same process, known as a redox reaction (reduction-oxidation).

In Terms of Oxygen Transfer

Term	Definition	Example
Oxidation	The gain of oxygen	Magnesium + oxygen → magnesium oxide (magnesium is oxidised)
Reduction	The loss of oxygen	Copper oxide + carbon → copper + carbon dioxide (copper oxide is reduced)

In Terms of Electron Transfer

Term	Definition	Memory aid
Oxidation	The loss of electrons	OIL — Oxidation Is Loss
Reduction	The gain of electrons	RIG — Reduction Is Gain