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WJEC · GCSE · Chemistry · Revision Notes

Energy Changes

52 words · Last updated July 2026

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What you'll learn

Energy in chemical reactions.

Key ideas

  • Exothermic (release) vs endothermic (absorb) reactions.
  • Activation energy; bond breaking (endo) and making (exo).

Exam tips

  • Combustion is exothermic.
  • Explain reactions using bond energies.

Common mistakes

  • Confusing exothermic and endothermic.
  • Reversing bond-making/breaking energy.
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