# A student is given two white solid substances, substance A and substance B. The student is told that one of these substances is a pure substance and the other is a mixture. Describe how the student could use melting point data to identify which substance is the pure substance and which is the mixture. In your answer, state the result expected for each substance.

> WJEC A-Level Chemistry (Wales) — 1.4 States of matter · Describe · 5 marks

## Mark scheme (5 marks)

1. Heat/measure the melting point of each substance (using a suitable method)
2. A pure substance melts at a specific/sharp temperature
3. A mixture melts over a range of temperatures
4. The substance (A or B) that shows a sharp melting point is the pure substance
5. The substance (A or B) that melts over a range of temperatures is the mixture

## Key terms

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

## Related

- [Revision notes for WJEC A-Level 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-is-given-two-white-742e1cc0) · Published by Druglandscape Ltd.