Скачать или смотреть GCSE Chemistry Required Practical 6 | Paper Chromatography (AQA)

Learn the GCSE Chemistry Required Practical – Paper Chromatography (AQA) in one clear video. This experiment shows how paper chromatography can separate mixtures of food colourings and how to use Rf values to help identify unknown substances.

In this video, we will:

Explain the aim: to investigate how paper chromatography can be used to separate and identify the coloured substances in an unknown mixture of food colourings.

Show the full apparatus setup: beaker, chromatography paper, pencil/wooden splint, capillary tubes, solvent (e.g. water), several known food colourings (A–D) and one unknown (U).

Walk through the step‑by‑step method: drawing a pencil baseline, spotting the known and unknown samples, placing the paper into a shallow layer of solvent below the line, allowing the solvent to rise, and removing and drying the chromatogram before the solvent reaches the top.

Demonstrate how to measure distances moved by each spot and the solvent front, then calculate Rf values using
Rf = distance travelled by substance ÷ distance travelled by solvent.

Show how to interpret the chromatogram:
Each spot = a different substance.
A pure substance gives one spot; a mixture gives several.
How to match the unknown’s spots to known colourings using position and Rf values.

Highlight key theory ideas: stationary phase vs mobile phase, why different substances travel different distances (different solubilities and attractions), and what an Rf value tells you.

Discuss sources of error and good practice: using pencil not pen, keeping the baseline above the solvent, making small, concentrated spots, keeping the beaker covered, and repeating if needed.

Practise exam‑style questions on this required practical, with model answers that use key phrases like “Rf value”, “pure substance”, “stationary phase”, “mobile phase” and “mixture of solutes”.
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