A surface along which the solvent (and any dissolved components) travels. It does not move during chromatography.

The movement of a solvent and any dissolved components of a sample along the stationary phase in chromatography.

The resultant pattern of a sample’s components on the stationary phase after chromatography has been carried out.

A type of chromatography that uses a thin layer of an inert substance spread over an unreactive flat surface as the stationary phase and a liquid state substance for the mobile phase.

A type of chromatography that uses an inert substance packed into a coiled tube as the stationary phase and an unreactive/inert gas as the mobile phase.

Comparing types of chromatography: including gas chromatography

Combined science

In the Making Salts unit, pupils will build on their understanding of separation techniques to learn about the process of making salts and writing balanced chemical equations.

In the Separation Techniques unit, pupils learned about various methods for separating mixtures, including filtration, evaporation, distillation, and chromatography.

This unit explores purification techniques, including filtration, crystallisation, and distillation. It explains formulations, uses chromatographic methods to identify pure and impure substances, and interprets chromatograms with Rf values. The emphasis is on accurate measurements.

Separating substances

water is typically used as the mobile phase

volatile organic solvents are used as the mobile phase

Match the method of separation to the relevant statement.

Locating agents may be used in __________ to aid the analysis of a chromatogram.

Which type of chromatography provides information about the amount of each component present in a sample?

Which of these methods uses alumina or silica as the stationary phase?

Helium enables all the components of a sample to become visible.

Helium reacts with the alumina or silica in the stationary phase.

Why is helium used as a mobile phase in gas chromatography?

Retention times were measured for 3 substances using GC. Which substance had the greatest affinity with the stationary phase? Pentadecane (22.8 mins), decane (9.3 mins), octane (4.1 mins) or none?

two or more elements or compounds which are chemically combined

two or more elements cannot separated by physical or chemical methods

substances which cannot easily be separated physically

substances which are not chemically combined and can be physically separated

Which statement best describes a mixture?

furthest point reached by a solvent along the stationary phase

fixed medium through which a solvent, and components it contains, move

a liquid or gas that moves components it contains to separate them out

Match each keyword about chromatography to the relevant description.

How high up a piece of chromatography paper should the solvent be?

In chromatography, what information is required to calculate the retention factor of a substance?

How can you calculate the Rf value of this unknown component? The solvent front travelled 11.2 cm and the component travelled 6.8 cm on the chromatogram.

change the container used for the chromatography process

Chromatography was used to separate three unknown substances using the same solvent and stationary phase. Two different substances had the same Rf value. What could be done next to help identify them?

This lesson will be removed by end of Summer Term 2025.

Comparing types of chromatography: including gas chromatography

Lesson outcome

This lesson will be removed by end of Summer Term 2025.