Part 3 of 3

Measure travel, then reveal what you cannot see

Explain

Try it yourself

Explain: give reasons and connect them to evidence.

A spot centre travelled 24 mm from the baseline. The solvent front travelled 60 mm from that same line. Fill the gaps to calculate Rf and state whether it has a unit.

Fill the gaps

Spot distance (top of the fraction) / mm

Front distance (bottom of the fraction) / mm

Unit of Rf

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Scope and sources

Cambridge IGCSE Chemistry 0620 · 2026–2028 v2 · Original learning materials.

0620 Extended12.3.1–4: suitable solvent, coloured and colourless paper chromatography, known/unknown comparison, purity evidence and Rf. Bounded12.4.2 method choice. Illustrative data; no real practical or chemical identity certification.

Apparatus, amounts and times in the experiment are illustrative. Real practical work follows a teacher-approved safety method.

Official Cambridge syllabus