# Cold packs are used in sports medicine to treat injuries. When a cold pack is activated, ammonium nitrate dissolves in water inside the pack. The temperature of the pack drops significantly, making the surrounding skin feel cold. Explain why the temperature drops when the cold pack is activated, referring to the overall energy change of the reaction and the processes of bond breaking and bond making.

> OCR A-Level Chemistry A (H432) — 3.2 Physical chemistry · Explain · 5 marks

> Cold packs are single-use devices used by physiotherapists on sports pitches. When squeezed, the pack activates and rapidly becomes cold enough to reduce swelling in an injured joint.

## Mark scheme (5 marks)

1. The dissolving process is an endothermic reaction / change
2. Energy is taken in from the surroundings (the skin / the environment)
3. The energy needed to break bonds in the reactants is greater than the energy released when bonds in the products are formed
4. Bond breaking is an endothermic process (requires / takes in energy)
5. The overall energy change is positive / the products have more energy than the reactants, so the temperature of the surroundings decreases

## Key terms

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

## 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/cold-packs-are-used-in-sports-421da919) · Published by Druglandscape Ltd.