# Hand warmers contain iron powder. When the pack is opened and exposed to air, the iron reacts with oxygen in an exothermic reaction, releasing energy to warm the hands. Explain, in terms of bonds and energy transfer to the surroundings, why this reaction is exothermic, and describe what happens to the temperature of the surroundings during the reaction.

> OCR A-Level Chemistry B: Salters (H433) — 3.2 Physical chemistry · Explain · 5 marks

> Hand warmers contain iron powder. When the pack is opened and exposed to air, the iron reacts with oxygen in an exothermic reaction.

## Mark scheme (5 marks)

1. In an exothermic reaction, energy is transferred to the surroundings
2. Bond breaking is an endothermic process (requires energy input)
3. Bond making is an exothermic process (releases energy)
4. The energy released in bond making is greater than the energy required for bond breaking / more energy is released than taken in overall
5. The temperature of the surroundings increases

## Key terms

- [exothermic reaction](https://www.gradenine.co.uk/glossary/exothermic-reaction)
- [surroundings](https://www.gradenine.co.uk/glossary/surroundings)

## Related

- [Revision notes for OCR A-Level Chemistry B: Salters (H433)](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-iron-powder-when-725bf9ef) · Published by Druglandscape Ltd.