# A supplier claims that a sample of water is pure. A student measures the melting point of the water sample and finds that it melts over a range of temperatures between −2 °C and 0 °C. Explain what this result tells the student about the water sample.

> Eduqas GCSE Chemistry — 1.3 Water · Explain · 4 marks

## Mark scheme (4 marks)

1. A pure substance melts at a single/sharp melting point (not over a range)
2. The sample melts over a range of temperatures, so it is not a pure substance / it is a mixture
3. The sample contains at least one other substance mixed with the water (i.e. it is a mixture)
4. Therefore the supplier's claim is incorrect / the sample is not pure water

## Key terms

- [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-supplier-claims-that-a-sample-b4bf040d) · Published by Druglandscape Ltd.