A lesson on paper chromatography in 2 minutes. Use for GCSE science catch-up/booster, GCSE science revision, GCSE science exam consolidation or just for your pure enjoyment. Try the experiment for yourself. If it's going too fast, stop on the relevant parts for your understanding.
Paper chromatography
is used to separate a mixture of two soluble substances. It can be used to distinguish between pure and impure substances. Examples are inks and food dyes.
Paper chromatography involves a
stationary phase and a mobile phase. The mobile phase is the solvent, and it is absorbed by the stationary phase, the chromatography paper. As the mobile phase moves up the stationary phase the solvent dissolves the ink and separates the colours.
Separation by chromatography produces a
chromatogram.
A pure substance will produce one spot on a chromatogram. An impure substance will produce two or more spots on a chromatogram.
Chromatography can be used to identify unknown substances by calculating an Rf Value.
The Rf value is calculated using the following formula:
Distance travelled by substance
Distance travelled by solvent