# A student measures the mass of a small stone as 0.0035 kg. Explain how the student could express this measurement using a more appropriate prefix, and state which prefix and unit combination should be used.

> Edexcel GCSE Physics (1PH0) — 1.1 Key concepts of physics · Explain · 4 marks

> A student is recording measurements in a physics experiment. They write down the mass of a small stone as 0.0035 kg.

## Mark scheme (4 marks)

1. Identifies that the measurement 0.0035 kg contains an inconvenient number of decimal places / zeros, making it difficult to work with or read clearly
2. States that a prefix can be used to replace the power of ten / scale the unit to give a more manageable number
3. Correctly identifies the prefix 'milli' (m) as appropriate, equivalent to ×10⁻³
4. States the correctly expressed value with the correct unit: 3.5 g or 3.5 milligrams (mg) — accept grams as the unit here since 1 g = 10⁻³ kg; award mark for 3.5 mg with unit stated

## Key terms

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

## Related

- [Revision notes for Edexcel GCSE Physics (1PH0)](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-measures-the-mass-of-be2f8bf0) · Published by Druglandscape Ltd.