# A student investigates the reaction between marble chips (calcium carbonate) and dilute hydrochloric acid. She carries out two experiments using the same mass of marble chips and the same volume of acid, but in one experiment she uses large chips and in the other she uses small chips of the same total mass. Describe and explain the difference in the rate of reaction observed between the two experiments.

> Cambridge International IGCSE Chemistry (0620) — 6.2 Rate of reaction · Describe and explain · 4 marks

## Mark scheme (4 marks)

1. The small chips react faster / at a greater rate than the large chips
2. Small chips have a greater/larger surface area (than large chips of the same mass)
3. More reactant particles are exposed / available for collisions at the surface
4. More (frequent/successful) collisions occur per unit time, so the rate increases

## Key terms

- [rate of reaction](https://www.gradenine.co.uk/glossary/rate-of-reaction)

## Related

- [Revision notes for Cambridge International IGCSE Chemistry (0620)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe and 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-investigates-the-reaction-between-f81145e2) · Published by Druglandscape Ltd.