Neutralisation is described as an exothermic reaction. Using ideas about bond breaking and bond forming, explain why the temperature of the surroundings increases during a neutralisation reaction.

Eduqas GCSE Chemistry — C5 Energy changes · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

Energy must be supplied to break bonds in the reactants. Energy is released when new bonds are formed in the products. The energy released from forming new bonds is greater than the energy needed to break existing bonds. The excess energy is transferred to the surroundings, causing the temperature to increase.

Examiner tips

  • Use the word ‘excess’ or ‘surplus’ to show the net release of energy.
  • Show the energy flow: break → release → transfer to surroundings.
  • Mention that the reaction is exothermic because the enthalpy change is negative.
  • Use the term ‘surroundings’ to match the wording of the question.

Common mistakes

  • Failing to state that energy is supplied to break bonds.
  • Confusing the direction of energy transfer (e.g., saying energy is absorbed by surroundings).
  • Using vague terms like ‘more energy’ without explaining the comparison of bond energies.

Mark scheme (4 marks)

  1. Energy must be supplied to break bonds in the reactants
  2. Energy is released when new bonds are formed in the products
  3. The energy released from forming new bonds is greater than the energy needed to break existing bonds
  4. The excess/surplus energy is transferred to the surroundings, causing the temperature to increase

Key terms in this question

exothermic reaction · bond breaking · bond forming · surroundings

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