# A student is investigating how the volume of gas produced changes over time when zinc granules react with dilute sulfuric acid. The student collects the gas in a gas syringe and records the volume every 30 seconds. Describe how the student should carry out this investigation to obtain valid and reliable results, and explain how the results would show when the reaction has finished.

> OCR A-Level Chemistry B: Salters (H433) — 1.1 Practical skills assessed · Describe · 5 marks

> Zinc granules react with dilute sulfuric acid to produce zinc sulfate solution and hydrogen gas. The student wants to investigate how the volume of gas produced changes over time.

## Mark scheme (5 marks)

1. Measure and record a fixed/constant mass or amount of zinc granules for each repeat
2. Measure and use the same volume and concentration of sulfuric acid each time
3. Record the volume of gas in the syringe at regular time intervals (every 30 seconds)
4. Repeat the experiment at least once more and calculate a mean / repeat to check for anomalous results
5. The reaction has finished when the volume of gas in the syringe stops increasing / remains constant over successive readings

## Key terms

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

## Related

- [Revision notes for OCR A-Level Chemistry B: Salters (H433)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" 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-how-the-3abf405f) · Published by Druglandscape Ltd.