Chromatography comes up again and again in IGCSE Chemistry Paper 6, often as a diagram with mistakes to find. Here you compare a green food colouring with three known food dyes, using water as the solvent. Watch the set-up built step by step, then build it yourself and check it 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: 0620/62 February/March 2025, (finding the errors in a chromatography set-up for inks) · official past papers
Practise next: 0620/61 October/November 2023, (where the spots and solvent go, when to remove the paper) · official past papers
Practise next: 0620/61 October/November 2024, (planning: how many coloured compounds are in beetroot) · official past papers
Examiner reports used: 0620 March 2023, November 2023, June 2024, November 2024, March 2025, June 2025 and November 2025 (Paper 6, with the Paper 2, 3 and 4 comments on chromatography).
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What a full-mark diagram shows
The paper
Chromatography paper with a baseline drawn in pencil about 2 cm from the bottom, and small, concentrated spots of each sample on the line.
The beaker
Solvent touching the bottom of the paper but below the baseline, and a lid on the beaker.
Running it
Remove the paper shortly before the solvent reaches the top, mark the solvent front in pencil at once, then dry it.
The results
Rf = distance moved by spot ÷ distance moved by solvent, both measured from the baseline. No unit. A locating agent shows colourless spots.
Habits the examiner reports keep asking for
Pencil, not pen, for the baseline: graphite does not dissolve in the solvent.
Spots go on the baseline, and the solvent stays below it.
Keep the lid on. “The lid should not be used” was a common wrong answer.
Take the paper out shortly before the top, not “when the spots stop moving”.
Write a conclusion, not a description: which samples are single substances, and which dyes a mixture contains.