Test for oxygen — AQA GCSE Combined Science
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Test for oxygen explained
Oxygen is identified by its effect on a glowing splint.
Read the full explanation
Light a splint, blow it out so it is still glowing, then insert the glowing splint into a test tube containing the gas. In oxygen, the splint relights because oxygen supports combustion. The test works because the gas is an oxidising agent and allows the wood to burn more vigorously. Do not use a burning splint, because that tests for hydrogen and gives a pop. Do not confuse 'relights' with 'burns more brightly'; the expected observation is that the glowing splint relights. The test is assessed by describing the correct procedure and the positive result, and by distinguishing oxygen from hydrogen, which gives a pop with a burning splint.
Your focus
- Describe the procedure for the test for oxygen using a glowing splint.
- State the positive result: the glowing splint relights in oxygen.
- Explain why oxygen causes a glowing splint to relight, in terms of supporting combustion.
Test for oxygen exam tips
Marking Points
- A glowing splint is inserted into a test tube containing the gas.
- The splint relights in oxygen.
- The splint must be glowing, not burning, before it is inserted.
- Oxygen supports combustion, which is why the glowing splint relights.
- The test is positive only for oxygen; hydrogen gives a pop with a burning splint instead.
Examiner Tips
- 💡State both the procedure and the result: 'Insert a glowing splint into the test tube; the splint relights in oxygen.'
- 💡Use the word 'glowing' rather than 'burning' when describing the splint for the oxygen test.
- 💡If asked to compare tests, contrast the glowing splint relighting for oxygen with the burning splint pop for hydrogen.
Common Mistakes
- Using a burning splint instead of a glowing splint: a burning splint tests for hydrogen; for oxygen the splint must be glowing.
- Saying the splint 'burns brightly' rather than 'relights': the expected observation is that it relights.
- Inserting the splint without first making it glow: a cold splint will not relight; light it and blow it out until it glows.