Testing for oxygen: a glowing splint relights
Definition
Oxygen
The gas that makes up about one-fifth, or approximately 20%, of Earth's atmosphere.
Definition
Glowing splint
A wooden splint with a glowing, smouldering tip rather than a flame, used to test for oxygen because oxygen relights it.
- Collect the gas and lower a glowing splint into the test tube.
- If oxygen is present, the glowing splint relights and bursts back into flame.
- Oxygen supports combustion, so it makes the smouldering splint burn again.
- There is no colour change or sound; the relighting is the positive result.
Exam technique
- State the glowing splint and that it relights; relights is the word examiners want.
- Do not write that the splint simply keeps glowing, as it does that in ordinary air too.
Why it works and common slips
- A glowing splint has a hot tip but no flame; the extra oxygen lets it reignite.
- Do not use a burning splint, because that is the test for hydrogen.
- Air is only about 20%20\%20% oxygen, so a splint keeps glowing in air but only relights in a gas that is much richer in oxygen.
Self review
- What do you use to test for oxygen?
- What is the positive result for oxygen?
- Why does oxygen relight a glowing splint?
- How is the oxygen test different from the hydrogen test?
