# A student wants to find out whether a sample of a white solid is a pure substance or a mixture. Describe how the student could use melting point data to determine this, and explain what results would be expected for a pure substance compared to a mixture.

> WJEC GCSE Chemistry (Wales) — 1.5 Rate of chemical change · Describe · 4 marks

## Mark scheme (4 marks)

1. Heat the solid and record the temperature at which it melts / measure the melting point of the solid
2. A pure substance melts at a specific/sharp temperature (not a range)
3. A mixture melts over a range of temperatures (not at one fixed point)
4. Compare the measured melting point to the known/data book value to confirm identity of a pure substance

## Key terms

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

## Related

- [Revision notes for WJEC GCSE Chemistry (Wales)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" 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-wants-to-find-out-5a738c3d) · Published by Druglandscape Ltd.