# A student uses a hot water bottle to keep warm in bed. The hot water bottle starts at a high temperature and gradually cools down until it reaches room temperature. Explain what happens to the energy stored in the hot water bottle during this process, and why the total energy of the closed system does not change.

> AQA GCSE Physics (8463) — 4.1.2 Conservation and dissipation of energy · Explain · 4 marks

## Mark scheme (4 marks)

1. Thermal energy is transferred from the hot water bottle to the surroundings
2. The energy is dissipated / spread out into the surroundings
3. Energy cannot be created or destroyed (conservation of energy)
4. The energy lost by the hot water bottle equals the energy gained by the surroundings, so the total energy of the closed system stays the same

## Key terms

- [closed system](https://www.gradenine.co.uk/glossary/closed-system)

## Related

- [Revision notes for AQA GCSE Physics (8463)](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-uses-a-hot-water-9e881cd2) · Published by Druglandscape Ltd.