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.
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
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)