# Hand warmers are small packets used by skiers and hikers to keep their hands warm. Inside a hand warmer, iron powder reacts with oxygen from the air. Explain why a hand warmer becomes warm when it is activated, and describe what this tells us about the overall energy change of the reaction.

> OCR GCSE Chemistry A: Gateway Science (J248) — C3.1 Introducing chemical reactions · Explain · 4 marks

> Hand warmers are single-use devices that produce heat when a packet is opened and exposed to air. The iron powder inside reacts with oxygen to form iron oxide.

## Mark scheme (4 marks)

1. The reaction transfers energy to the surroundings
2. The temperature of the surroundings increases
3. This means the reaction is exothermic
4. The energy released when bonds form in the products is greater than the energy needed to break bonds in the reactants / the overall energy change is negative

## Key terms

- [overall energy change](https://www.gradenine.co.uk/glossary/overall-energy-change)

## Related

- [Revision notes for OCR GCSE Chemistry A: Gateway Science (J248)](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-are-small-packets-used-61215aa9) · Published by Druglandscape Ltd.