Figure 1: The four key gas tests — O₂ re-lights a glowing splint, H₂ gives a squeaky pop, CO₂ turns limewater milky, Cl₂ bleaches damp litmus white.
The Five Key Gas Tests
- Hydrogen (H₂): Burning splint test — "squeaky pop"
- Oxygen (O₂): Glowing splint test — relights the splint
- Carbon dioxide (CO₂): Limewater test — turns milky/cloudy
- Chlorine (Cl₂): Damp blue litmus paper — bleaches to white
- Ammonia (NH₃): Damp red litmus — turns blue; or white fumes with HCl rod
This diagram covers The Five Key Gas Tests within Gas Tests for GCSE Chemistry. Revise Gas Tests in Chemical Analysis for GCSE Chemistry with 20 exam-style questions and 15 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 3 of 13 in this topic. Focus on the labels, the relationships between parts, and the explanation that turns the diagram into an exam-ready answer.
Practice questions for Gas Tests
Which observation confirms a gas is hydrogen when tested with a burning splint?
Explain why hydrogen gas produces a squeaky pop when tested with a burning splint.
Quick recall flashcards
Test for oxygen gas (O₂)?
Use a glowing splint (blow out flame first). POSITIVE RESULT: Glowing splint relights/bursts into flame (O₂ supports combustion)
Test for hydrogen gas (H₂)?
Use a burning splint. POSITIVE RESULT: 'Squeaky pop' sound (H₂ burns rapidly: 2H₂ + O₂ → 2H₂O)