GCSE Chemistry: Energy Changes Revision

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In an exothermic reaction, what happens energetically with the bonds?

Energy Changes is a core part of GCSE Chemistry. Revise the key concepts and common mistakes below, then lock them in with the free games.

Key concepts

ExothermicReaction that releases energy to surroundings (T rises)

EndothermicReaction that takes in energy (T falls)

Activation energyMinimum energy needed for a reaction to start

Bond breakingEndothermic step: energy must be taken in to break bonds.

Bond makingExothermic step — energy is given out

Reaction profileGraph of energy vs progress of reaction

Hand warmerUses an exothermic reaction to release heat

Cold packUses an endothermic reaction to absorb heat

CalorimetryMeasuring heat change by recording temperature rise

Energy per gramHeat released ÷ mass of fuel burned (J/g or kJ/g)

Reusable warmerUses a reversible exothermic crystallisation

Bond energyEnergy to break 1 mole of a specific bond (kJ/mol)

Energy inTotal energy needed to break all the reactant bonds; overall energy change = energy in − energy out.

What your exam board covers

Where Energy Changes sits in each exam board's specification. Tap a board to see what it lists.

AQAEnergy changesSpec 8462

Exothermic and endothermic reactions
Chemical cells and fuel cells (chemistry only)

Source: AQA GCSE Chemistry (8462) specification — Subject content, accessed 23 June 2026.

EdexcelTopic 7 — Rates of reaction and energy changesSpec 1CH0

Part of: Paper 2 topics

Source: Pearson Edexcel GCSE (9–1) Chemistry (1CH0) specification, accessed 23 June 2026.

Eduqas/WJECEnergy changes in chemistrySpec C410P (QAN 601/8640/9)

Exothermic and endothermic reactions
Energy changes and bond energies

Source: Eduqas/WJEC GCSE Chemistry specification (from 2016), accessed 24 June 2026.

Learn Energy Changes step by step

Free interactive mini-lessons: short screens, worked examples and quick checks. Pick your exam board:

Other boards:CCEA OCR Cambridge IGCSE Edexcel IGCSE

Common mistakes to avoid

Questions where students often pick the tempting wrong answer — make sure you know the right one:

In an exothermic reaction, what happens energetically with the bonds?✗ Bond breaking releases energy and bond making absorbs energy. ✓ Energy released forming new bonds exceeds energy absorbed breaking existing bonds.

Which statement about bonds is correct?✗ Breaking bonds releases energy ✓ Breaking bonds takes energy in; making bonds releases energy

A sports cold pack contains ammonium nitrate and water. When squeezed, it gets cold. The reaction is.✗ Exothermic — releases heat ✓ Endothermic — takes in heat

Why is the experimental value for a fuel's energy per gram usually lower than the true value?✗ The thermometer reads too high ✓ Heat is lost to the surroundings

Practise Energy Changes — free games

Test yourself with these quick revision games for this topic:

▶ Two Truths, One Lie ▶ Reveal Race ▶ Connections Grid ▶ Falling Words ▶ Word Web

See all 22 games in the Revision Arcade →

Energy Changes

Key concepts

What your exam board covers

Common mistakes to avoid

Practise Energy Changes — free games

More GCSE Chemistry topics