# Hand warmers contain chemicals that undergo an exothermic reaction when activated. A student claims that adding a catalyst to the hand warmer mixture would make it release heat faster without changing the total amount of heat released. Explain why the student's claim is correct, referring to activation energy and the reaction profile.

> OCR A-Level Chemistry A (H432) — 5.2 Energy · Explain · 5 marks

> Hand warmers are single-use packets used by hikers and athletes. They contain a chemical mixture that reacts when exposed to air, releasing heat that warms the user's hands.

## Mark scheme (5 marks)

1. A catalyst provides a different reaction pathway with a lower activation energy
2. More particles have (at least) the activation energy, so the rate of reaction increases / heat is released faster
3. The catalyst is not used up / not consumed during the reaction
4. The overall energy change (difference in energy between reactants and products) remains the same
5. On the reaction profile, the peak (transition state) is lower with the catalyst but the energy levels of reactants and products are unchanged, so the total heat released is the same

## Key terms

- [activation energy](https://www.gradenine.co.uk/glossary/activation-energy)
- [catalyst](https://www.gradenine.co.uk/glossary/catalyst)
- [reaction profile](https://www.gradenine.co.uk/glossary/reaction-profile)
- [exothermic](https://www.gradenine.co.uk/glossary/exothermic)

## Related

- [Revision notes for OCR A-Level Chemistry A (H432)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/hand-warmers-contain-chemicals-that-undergo-2d07679d) · Published by Druglandscape Ltd.