Energy changes in reactions
Edexcel GCSE Chemistry revision on Energy changes in reactions. Aligned to the Pearson Edexcel GCSE Chemistry 1CH0 specification. This bank has 8 practice questions on this topic.
Sample questions (3 of 8)
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Question 1
An exothermic reaction is one that...
- A) Absorbs heat from the surroundings
- B) Releases heat to the surroundings
- C) Stays at the same temperature
- D) Only happens in cold water
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Answer: Releases heat to the surroundings
Examples of exothermic: combustion (burning), neutralisation, oxidation of metals, hand warmers, respiration. Energy released as heat (sometimes light). Energy diagram: products at LOWER energy than reactants (energy 'released'). Most spontaneous reactions are exothermic - heat the surroundings.
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Question 2
An endothermic reaction is one that...
- A) Releases heat to the surroundings
- B) Absorbs heat from the surroundings
- C) Doesn't happen at all
- D) Always explosive
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Answer: Absorbs heat from the surroundings
Examples of endothermic: photosynthesis, thermal decomposition, sports cold packs, melting ice, dissolving ammonium nitrate. Energy required - needs to come from somewhere (heat in surroundings). Energy diagram: products at HIGHER energy than reactants. Less common in everyday life than exothermic reactions.
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Question 3
Bond breaking is ___ ; bond making is ___ .
- A) endothermic ; exothermic
- B) exothermic ; endothermic
- C) exothermic ; exothermic
- D) endothermic ; endothermic
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Answer: endothermic ; exothermic
Breaking bonds is ALWAYS endothermic (you have to put energy IN to pull atoms apart). Making bonds is ALWAYS exothermic (energy released as atoms snap together). For an overall EXOTHERMIC reaction: energy released by new bonds > energy absorbed breaking old bonds. For ENDOTHERMIC: more energy absorbed than released. Net energy change = bonds broken - bonds formed (using bond energies).
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5 more questions on Energy changes in reactions — plus mistakes tracking and spaced repetition across the whole Chemistry spec.