# Explain why placing a hot drink in a vacuum flask with a shiny inner surface helps to keep the drink warm for longer. In your answer, refer to conduction, convection and radiation.

> Cambridge International IGCSE Physics (0625) — 2.3 Transfer of thermal energy · Explain · 4 marks

## Mark scheme (4 marks)

1. The vacuum (between the double walls) prevents thermal energy transfer by conduction and/or convection
2. Conduction and/or convection require particles/a medium to transfer energy, which are absent in a vacuum
3. The shiny inner surface is a poor emitter of thermal radiation
4. The shiny inner surface reflects thermal radiation back into the drink / reduces energy lost by radiation

## Key terms

- [vacuum](https://www.gradenine.co.uk/glossary/vacuum)
- [conduction](https://www.gradenine.co.uk/glossary/conduction)
- [convection](https://www.gradenine.co.uk/glossary/convection)
- [radiation](https://www.gradenine.co.uk/glossary/radiation)

## Related

- [Revision notes for Cambridge International IGCSE Physics (0625)](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/explain-why-placing-a-hot-drink-d5aa95fd) · Published by Druglandscape Ltd.