# A student obtains a sample of a white solid and wants to find out whether it is a pure substance or a mixture. Describe how the student could use melting point data to determine whether the white solid is pure, and explain what results would indicate that the solid is a pure substance.

> Eduqas A-Level Chemistry — 1.6 Kinetics · Describe · 5 marks

> The student has access to standard laboratory equipment and a data book containing melting points of known pure substances.

## Mark scheme (5 marks)

1. Heat the solid and record the temperature at which it melts
2. A pure substance melts at a single, sharp (specific) temperature
3. A mixture melts over a range of temperatures
4. Compare the recorded melting point to the known melting point of the expected pure substance (from a data book)
5. If the solid melts sharply at the same temperature as the known value, it is a pure substance

## Key terms

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

## Related

- [Revision notes for Eduqas A-Level Chemistry](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-obtains-a-sample-of-31be9089) · Published by Druglandscape Ltd.