# A student pours a small amount of perfume onto a cotton wool ball and places it in the corner of a room. After a short time, the scent of the perfume can be detected on the opposite side of the room. Explain, using the particle model, why the perfume can be smelt across the room, and why the scent reaches the far side of the room more quickly on a warm day than on a cold day.

> OCR GCSE Physics A: Gateway Science (J249) — P1.1 The particle model · Explain · 4 marks

> Perfume is a liquid at room temperature. When it evaporates, its particles enter the air as a gas.

## Mark scheme (4 marks)

1. The perfume evaporates / changes from liquid to gas, so its particles enter the air
2. Gas particles move / spread out randomly in all directions, carrying the scent across the room
3. On a warmer day, the particles have greater kinetic energy / move faster
4. Faster-moving particles spread across the room in less time, so the scent arrives more quickly

## Key terms

- [particle model](https://www.gradenine.co.uk/glossary/particle-model)

## Related

- [Revision notes for OCR GCSE Physics A: Gateway Science (J249)](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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Source: [GradeNine](https://www.gradenine.co.uk/q/a-student-pours-a-small-amount-954f1870) · Published by Druglandscape Ltd.