This exam focus covers Exam Focus within Gas Tests for GCSE Chemistry. Revise Gas Tests in Chemical Analysis for GCSE Chemistry with 20 exam-style questions and 15 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 11 of 13 in this topic. Treat this as a marking guide for what examiners are looking for, not just a fact list.
Topic position
Section 11 of 13
Practice
20 questions
Recall
15 flashcards
🎯 Exam Focus
Very High Frequency
What Examiners Ask About Gas Tests
- "Describe the test for hydrogen/oxygen/CO₂/chlorine" — state method AND positive result (2 marks each)
- "Explain why limewater turns milky" — must mention CaCO₃ precipitate (2 marks)
- "Why must the litmus paper be damp?" — water needed for the reaction with chlorine (1 mark)
- "What is the difference between the hydrogen and oxygen tests?" — burning vs glowing splint (2 marks)
- Write or complete the equation for one of the gas test reactions (2 marks)
Marks at Risk
- Saying "burning splint" for oxygen — always "glowing splint"
- Vague descriptions — say exactly "squeaky pop", "relights", "turns milky", "bleaches white"
- Forgetting "damp" for chlorine and ammonia tests