# When hand warmers are used, an exothermic reaction occurs inside the pack. Explain, in terms of bond breaking and bond forming, why the temperature of the hand warmer increases during this reaction.

> Edexcel GCSE Chemistry (1CH0) — 7.2 Heat energy changes in chemical reactions · Explain · 4 marks

> Hand warmers are single-use packs that become hot when activated. They are used by athletes and outdoor workers in cold weather.

## Mark scheme (4 marks)

1. Energy is required / taken in 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. This means there is a net transfer of energy to the surroundings, so the temperature of the hand warmer increases

## Key terms

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

## Related

- [Revision notes for Edexcel GCSE Chemistry (1CH0)](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/when-hand-warmers-are-used-an-3e1cac2a) · Published by Druglandscape Ltd.