This definitions covers Key Definitions 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 7 of 13 in this topic. Make sure you can use the exact wording confidently, because definition marks are often lost through vague language.
📖 Key Definitions
Limewater: A clear, colourless solution of calcium hydroxide (Ca(OH)₂). It turns milky/cloudy in the presence of carbon dioxide due to formation of a white precipitate of calcium carbonate.
Positive result: The specific, characteristic observation that confirms the presence of a particular substance in a test.
Bleaching: The destruction of colour in a substance, often by oxidation. Chlorine bleaches damp litmus paper because it forms hypochlorous acid which oxidises the dye molecules.
Combustion: A reaction in which a substance reacts rapidly with oxygen, releasing energy as heat and light.
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.