# A student places a piece of potato in a very dilute sugar solution. After 30 minutes, the potato piece becomes firm and slightly heavier. Explain why the mass of the potato piece increased.

> WJEC GCSE Biology (Wales) — 1.1.2 Movement of substances · Explain · 4 marks

## Mark scheme (4 marks)

1. Water moves into the potato cells by osmosis
2. The sugar solution outside is more dilute than the cell contents (higher water concentration outside / lower solute concentration outside)
3. Water moves down a concentration gradient (from high water concentration to low water concentration)
4. Water enters through the partially permeable membrane, increasing the mass/making cells turgid

## Related

- [Revision notes for WJEC GCSE Biology (Wales)](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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