# A student places a cold pack on a sports injury. The cold pack contains ammonium nitrate and water in separate compartments. When the pack is squeezed, the compartments break and the chemicals mix, causing the pack to feel cold against the skin. Explain why the cold pack feels cold, referring to bonds and energy transfer.

> OCR GCSE Chemistry A: Gateway Science (J248) — C3.2 Energetics · Explain · 4 marks

> Cold packs are used in sports medicine to reduce swelling after an injury. They work through a chemical reaction that occurs when the pack is activated.

## Mark scheme (4 marks)

1. The reaction is endothermic
2. Energy is taken in from the surroundings (the skin / the environment)
3. More energy is required to break bonds in the reactants than is released when bonds form in the products
4. The temperature of the surroundings decreases, so the pack feels cold

## 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/a-student-places-a-cold-pack-bd41cebb) · Published by Druglandscape Ltd.