AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
Test for hydrogen: The test for hydrogen uses a burning splint held at the open end of a test tube of the gas. Hydrogen burns rapidly with a pop sound.
Hydrogen is identified by its reaction with a burning splint.
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Hydrogen is identified by its reaction with a burning splint. Collect the gas in a test tube, light a splint, then hold the burning splint at the open end of the tube. Hydrogen burns rapidly with oxygen from the air, producing a squeaky pop. The test works because hydrogen is flammable and reacts exothermically: 2H₂ + O₂ → 2H₂O. The pop is the rapid expansion of hot gases and water vapour. Do not insert the splint into the tube, because the gas may not be mixed with enough oxygen and the pop can be weaker or the flame may be extinguished. The test is assessed by describing the correct procedure and the positive result, and by distinguishing hydrogen from other gases such as oxygen, which relights a glowing splint.
What earns the marks
- A burning splint is held at the open end of a test tube containing the gas.
- Hydrogen burns rapidly and produces a pop sound.
- The reaction is hydrogen reacting with oxygen from the air to form water: 2H₂ + O₂ → 2H₂O.
- The test is positive only when a burning splint is used, not a glowing splint.
- The splint should not be inserted deep into the test tube; it is held at the open end.
Common mistakes and how to put them right
Using a glowing splint instead of a burning splint.
Put it right: A glowing splint tests for oxygen, not hydrogen; always light the splint first.
Saying hydrogen relights a glowing splint.
Put it right: That is the oxygen test; hydrogen gives a pop with a burning splint.
Inserting the burning splint into the tube.
Put it right: This can extinguish the flame or give a weak result; hold it at the open end.
Exam tips
- State both the procedure and the result: 'Hold a burning splint at the open end of the test tube; a pop sound shows hydrogen.'.
- Use the word 'burning' rather than 'lit' or 'glowing' when describing the splint.
- If asked to compare tests, contrast the burning splint pop for hydrogen with the glowing splint relighting for oxygen.
Try the lesson
The start of the Test for hydrogen: The test for hydrogen uses a burning splint held at the open end of a test tube of the gas. Hydrogen burns rapidly with a pop sound. lesson, made from checked teaching notes for this specification point.
Have a go first
Which gas gives a squeaky pop when a burning splint is held at the open end of a test tube of the gas?
Listen
Hydrogen is identified by its reaction with a burning splint. Collect the gas in a test tube, light a splint, then hold the burning splint at the open end of the tube. Hydrogen burns rapidly with oxygen from the air, producing a squeaky pop. The test works because hydrogen is flammable and reacts exothermically: 2H₂ + O₂ → 2H₂O. The pop is the rapid expansion of hot gases and water vapour. Do not insert the splint into the tube, because the gas may not be mixed with enough oxygen and the pop can be weaker or the flame may be extinguished. The test is assessed by describing the correct procedure and the positive result, and by distinguishing hydrogen from other gases such as oxygen, which relights a glowing splint. A strong answer earns marks for these points. A burning splint is held at the open end of a test tube containing the gas. Hydrogen burns rapidly and produces a pop sound. The reaction is hydrogen reacting with oxygen from the air to form water: 2H₂ + O₂ → 2H₂O. The test is positive only when a burning splint is used, not a glowing splint. Exam tip: State both the procedure and the result: 'Hold a burning splint at the open end of the test tube; a pop sound shows hydrogen.
Key words
Say what each word means before you turn the card.
Burning splint
Try answering aloud or in your head before turning the card.
Pop sound
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Open end
Try answering aloud or in your head before turning the card.
Glowing splint
Try answering aloud or in your head before turning the card.
See every definition
- Burning splint
- A splint that is lit and held at the open end of a test tube of the gas, not inserted into the tube.
- Pop sound
- The sound heard when hydrogen burns rapidly with oxygen from the air, showing a positive test.
- Open end
- The position at the top of the test tube where the burning splint is held rather than inserted deep into the tube.
- Glowing splint
- A splint that tests for oxygen, not hydrogen, because hydrogen gives a pop with a burning splint.
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