Required Practical: Chromatography

This lesson covers paper chromatography, one of the required practicals for the AQA GCSE Chemistry specification (8.1.1). Chromatography is a technique used to separate and identify substances in a mixture, particularly useful for identifying unknown substances or checking the purity of a substance. You need to understand the method, how to calculate Rf values, and how to interpret chromatograms.

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What Is Chromatography?

Chromatography is a separation technique used to separate dissolved substances (solutes) from one another. It works because different substances have different solubilities in the solvent used, so they travel different distances through the stationary phase.

There are two phases in chromatography:

Phase	Description	Example in Paper Chromatography
Stationary phase	The phase that does not move	The chromatography paper
Mobile phase	The phase that moves through the stationary phase	The solvent (e.g., water, ethanol)