# A water treatment plant produces drinking water from river water. The river water contains sand particles and dissolved minerals. Describe how filtration and evaporation could be used in sequence to obtain a dry sample of the dissolved minerals from the river water.

> OCR GCSE Chemistry A: Gateway Science (J248) — C2.1 Purity and separating mixtures · Describe · 4 marks

> River water is a mixture containing insoluble particles such as sand and soluble dissolved minerals. Water treatment scientists use separation techniques to obtain pure samples of these components.

## Mark scheme (4 marks)

1. Filtration is used first to separate the insoluble sand from the river water / the sand is retained by the filter paper and the solution passes through as filtrate
2. The filtrate / solution containing dissolved minerals is then heated / the solution is placed in an evaporating dish and heated
3. The solvent (water) evaporates / is driven off, leaving behind the dry mineral crystals / solid
4. The correct order must be stated: filtration must be performed before evaporation / filtration removes insoluble sand first so that only the solution of dissolved minerals is then evaporated

## Key terms

- [filtration](https://www.gradenine.co.uk/glossary/filtration)
- [evaporation](https://www.gradenine.co.uk/glossary/evaporation)

## Related

- [Revision notes for OCR GCSE Chemistry A: Gateway Science (J248)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/a-water-treatment-plant-produces-drinking-8025289d) · Published by Druglandscape Ltd.