Dissolve, divide, add, observe. Then say what it shows.
Every 0620 Paper 6 has a question where a student tests two substances. Here solid A is dissolved and shared between four test-tubes for aqueous sodium hydroxide, aqueous ammonia, silver nitrate and barium nitrate, then given a flame test, and solid B is tested for the gases it gives off. Watch the tests set up step by step, then build them yourself and check them against the points the examiners look for.
Past-paper referenceOriginal experiment, wording and figures, written in the style of Cambridge IGCSE Chemistry 0620 Paper 6 (Alternative to Practical). It is not copied from a past paper. The “what the examiners said” notes are our paraphrase of the Principal Examiner Reports for Teachers.
Practise next: 0620/63 May/June 2024, (copper(II) ions with aqueous ammonia, and describing a flame test) · official past papers
Practise next: 0620/61 October/November 2025, (flame test, silver nitrate, and “no change” with sodium hydroxide) · official past papers
Practise next: 0620/62 February/March 2023, (ammonium test with damp red litmus, sulfate and carbonate) · official past papers
Examiner reports used: 0620 March 2023, June 2023, November 2023, June 2024, November 2024, March 2025, June 2025 and November 2025.
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What a full-mark diagram shows
Dissolve and divide
Dissolve the solid in distilled water and share the solution between test-tubes in a rack, one portion for each reagent.
Reagents
Add aqueous sodium hydroxide and aqueous ammonia with a dropping pipette, a little at a time and then in excess. Add dilute nitric acid before silver nitrate or barium nitrate.
Gas tests
Warm with aqueous sodium hydroxide and hold damp red litmus at the mouth of the tube; bubble the gas from dilute acid into limewater.
Flame test
A clean nichrome wire carries the solid into a roaring (blue) Bunsen flame, not near or over it.
Habits the examiner reports keep asking for
Describe the precipitate and its colour first, then say whether it dissolves in excess.
“No visible change” is an observation. A negative result tells you an ion is not there.
“A gas is given off” is not an observation. Write effervescence, and give the gas test result.
Say why a yellow flame is no good: it is not hot enough and its colour hides the flame colour.
Write colourless, not clear, and give oxidation states such as copper(II).