# A student is investigating whether the colour of a surface affects how quickly it cools. The student heats identical metal cans, one painted matt black and one left shiny and unpainted, to the same starting temperature. Explain how the student should carry out a fair test and why controlling variables is important in this investigation.

> OCR GCSE Physics A: Gateway Science (J249) — P9 Practical skills · Explain · 4 marks

> A student wants to find out if the colour of a metal surface affects the rate at which it loses heat to the surroundings. They have two identical metal cans, a thermometer, a stopwatch, and access to hot water.

## Mark scheme (4 marks)

1. The student must keep all variables the same except for the colour/surface of the can (e.g. same volume of water, same starting temperature, same room conditions, same time intervals)
2. Controlling variables ensures any difference in cooling rate is due to the surface colour and not another factor / makes it a fair test
3. The student should take repeat measurements / repeat the experiment for each can and calculate a mean temperature reading at each time interval
4. The student should identify and deal with anomalous results / outliers by checking and, if confirmed anomalous, excluding them from the mean

## Key terms

- [fair test](https://www.gradenine.co.uk/glossary/fair-test)
- [variable](https://www.gradenine.co.uk/glossary/variable)

## 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-is-investigating-whether-the-bae5f9c3) · Published by Druglandscape Ltd.