# A teacher heats a sample of candle wax and measures the temperature at which it melts. The candle wax melts over a range of temperatures from 52 °C to 61 °C. The teacher then heats a sample of naphthalene and finds that it melts sharply at 80 °C. Explain what these melting point results tell us about whether candle wax and naphthalene are pure substances.

> Eduqas GCSE Chemistry — 1.2 Atomic structure and the periodic table · Explain · 4 marks

## Mark scheme (4 marks)

1. Candle wax is not a pure substance / candle wax is a mixture
2. Because candle wax melts over a range of temperatures (rather than at a single/sharp temperature)
3. Naphthalene is a pure substance (a single element or compound)
4. Because naphthalene has a sharp/specific melting point (melts at one fixed temperature)

## Key terms

- [pure substance](https://www.gradenine.co.uk/glossary/pure-substance)
- [melting point](https://www.gradenine.co.uk/glossary/melting-point)

## Related

- [Revision notes for Eduqas GCSE Chemistry](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-teacher-heats-a-sample-of-c552bedd) · Published by Druglandscape Ltd.