# A student is trying to identify the gases produced during an experiment. Describe the tests a student would carry out to identify carbon dioxide gas and oxygen gas, including the expected results for each test.

> OCR GCSE Chemistry A: Gateway Science (J248) — C4.2 Identifying the products of chemical reactions · Describe · 4 marks

> During a chemistry experiment, two gases are collected separately in test tubes. The student needs to confirm which gas is carbon dioxide and which is oxygen.

## Mark scheme (4 marks)

1. Test for carbon dioxide: bubble the gas through limewater (calcium hydroxide solution)
2. Result for carbon dioxide: limewater turns cloudy / milky
3. Test for oxygen: place a glowing splint into the test tube of gas
4. Result for oxygen: the glowing splint relights

## Key terms

- [carbon dioxide](https://www.gradenine.co.uk/glossary/carbon-dioxide)
- [oxygen](https://www.gradenine.co.uk/glossary/oxygen)

## Related

- [Revision notes for OCR GCSE Chemistry A: Gateway Science (J248)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/a-student-is-trying-to-identify-33760b2f) · Published by Druglandscape Ltd.