Oxidation & Reduction

ChemistryAQAGCSEUnit: Chemical Changes
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The basics

The Electron Trade

📖 The Electron Trade

Imagine a bustling marketplace where atoms trade their most valuable possessions — electrons. Some atoms are eager sellers, desperate to give away their outer electrons. Others are hungry buyers, craving more electrons to fill their shells. Every time this trade happens, we call it a redox reaction. The atom that loses electrons gets "oxidised" (even if there's no oxygen in sight!), and the atom that gains electrons gets "reduced." This isn't just abstract chemistry — it's happening right now in the battery powering your phone, in the rusting of iron bridges, and in the photosynthesis happening in every leaf.
💰 The Money Exchange Analogy

Redox is like trading money between two people! When one person loses £10 (oxidation), someone else must gain that £10 (reduction). You can't have one without the other! The mnemonic OIL RIG helps: Oxidation Is Loss, Reduction Is Gain. Just remember: LEO the lion goes GER — Lose Electrons = Oxidation, Gain Electrons = Reduction!

What is a redox reaction?: A reaction where oxidation and reduction happen simultaneously
Key terms

Chemistry glossary

What is a redox reaction?
A reaction where oxidation and reduction happen simultaneously
Exam tip

Earn the mark scheme marks

🧠 Memory Aids

OIL RIG — the most important mnemonic in chemistry:

Oxidation Is Loss    Reduction Is Gain

Write OIL RIG in the margin of your exam paper the moment you start. It earns marks every time.

LEO GER — a second mnemonic:

Lose Electrons = Oxidation    Gain Electrons = Reduction

"LEO the lion goes GER" — lose electrons oxidation, gain electrons reduction.

Oxidising/reducing agents — the swap trick: "The oxidising agent is reduced. The reducing agent is oxidised." They do the opposite of what their name suggests happens to the other substance. Think: "The OXIDISING agent gets REDUCED (it gains electrons while making the other thing lose them)."

Electrolysis reminder: OARC — Oxidation At anode, Reduction at Cathode. The vowels: A (anode) = oxidation, C (cathode) = reduction.

Now try it yourself

Quiz · Question 1 of 20

What does OIL stand for in the mnemonic OIL RIG?

Tap an answer to check it

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