Chromatography has two phases, stationary and mobile, and separation depends on the distribution between these phases.
Both aqueous and non-aqueous solvents can be used in chromatography.
Chromatograms can be used to identify pure and impure substances.

Keywords

Chromatography - Chromatography is a technique that separates the components of a mixture, and the results can be analysed.
Mobile phase - The mobile phase is the movement of a solvent and any dissolved components of a sample along the stationary phase in chromatography.
Stationary phase - The stationary phase is a surface along which the solvent (and any dissolved components) travels. It does not move during chromatography.
Chromatogram - A chromatogram is the resultant pattern of a sample’s components on the stationary phase after chromatography has been carried out.

Common misconception

Pupils can struggle to interpret information that contains several samples on one chromatogram.

Stress a systematic approach to interpreting chromatograms (i.e. use rulers). Live modelling this using a visualiser helps enormously.

Pre-make chromatograms of pure and impure samples and challenge pupils to identify the pure components of the impure samples.

Teacher tip

Content guidance

Risk assessment required - equipment

Supervision

Adult supervision required

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

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Starter quiz

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6 Questions

Q1.

What is the role of a solvent in a solution?

Correct answer: to dissolve the solute

to react with the solute

to solidify the solute

to reduce the solute's temperature

to increase the solute's mass

Q2.

Which term describes a substance that cannot be dissolved in a particular solvent?

soluble

Correct answer: insoluble

solubility

solution

solute

Q3.

How does increasing the temperature of a substance generally affect the solubility of a solid in a liquid?

Correct answer: increases it

decreases it

does not affect it

Q4.

Match the separation technique to its most likely use.

Correct Answer:filtration,separating a liquid from an insoluble solid

separating a liquid from an insoluble solid

Correct Answer:distillation,separating liquids with different boiling points

separating liquids with different boiling points

Correct Answer:evaporation,recovering a dissolved solid from a solution

recovering a dissolved solid from a solution

Correct Answer:decanting,removing a liquid layer from a mixture

removing a liquid layer from a mixture

Q5.

Match the property to the type of mixture.

Correct Answer:uniform composition (e.g. sugar water),solution

solution

Correct Answer:layers form (e.g. oil and water),a mixture of immiscible liquids

a mixture of immiscible liquids

Correct Answer:particles settle (e.g. flour and water),suspension

suspension

Q6.

A solution in which more solute can be dissolved is described as ...

Correct Answer: unsaturated

Exit quiz

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6 Questions

Q1.

What is the main purpose of chromatography?

to change the composition of a mixture

Correct answer: to separate the components of a mixture

to increase the temperature of a mixture

to measure the volume of a mixture

to observe the colour changes in a mixture

Q2.

Match the following terms with their correct descriptions:

Correct Answer:chromatography,a technique that separates the components of a mixture

a technique that separates the components of a mixture

Correct Answer:mobile phase,the movement of a solvent and dissolved sample components

the movement of a solvent and dissolved sample components

Correct Answer:stationary phase,a surface along which the solvent travels and does not move

a surface along which the solvent travels and does not move

Correct Answer:chromatogram,the resultant pattern of a sample’s components after chromatography

the resultant pattern of a sample’s components after chromatography

Q3.

When analysing a chromatogram, what indicates that a substance is pure?

multiple spots of different colours

Correct answer: a single, distinct spot

no visible spots

spots that merge together

spots spread evenly across the chromatogram

Q4.

What is produced at the end of the chromatography process?

Correct Answer: chromatogram

Q5.

Order the following steps of paper chromatography correctly.

1 - Cut the chromatography paper to size.

2 - Draw a starting line (in pencil).

3 - Apply the sample(s) to the paper.

4 - Place the paper in a solvent.

5 - Wait for the solvent to travel up the paper.

6 - Observe the chromatogram.

Q6.

In chromatography, if a mixture contains three different components, how many distinct spots should you expect on the chromatogram?

Correct Answer: 3, three