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Year 7

Chromatography

I can describe how chromatography works and use a chromatogram to answer questions about a substance.

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Share activities with pupils
New
New
Year 7

Chromatography

I can describe how chromatography works and use a chromatogram to answer questions about a substance.

Download all resources
Share activities with pupils

Lesson details

Key learning points

  1. Chromatography can be used for both separation of minute samples and analysis.
  2. A pure substance will only produce one spot on a chromatogram.
  3. A mixture will produce many spots on a chromatogram.
  4. Comparing chromatograms can help to identify an unknown component in a sample.
  5. Pencil is insoluble in water.

Common misconception

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

Stress a systematic approach to interpreting chromatograms - use rulers. Live model this - using a visualiser helps enormously.

Keywords

  • Solvent - A solvent is a liquid into which a solute dissolves.

  • Soluble - When a substance dissolves in a liquid, it is described as soluble in that liquid.

  • Chromatography - Chromatography is a technique that separates a mixture into its different parts and the results can be analysed.

  • Chromatogram - A chromatogram is the resultant pattern on the stationary phase after chromatography has been carried out.

  • Compare - To compare is to look for similarities and/or differences between two things.

Create a mini-crime scene (e.g. stolen plant with a ransom note) and have students conduct chromatography on different pens to identify who wrote the note. Don't forget to make a chromatogram of the ransom note pen beforehand to use for comparison!
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.
If you have a mixture of sand and salt, adding water will dissolve the salt. What will happen to the sand?
An image in a quiz
It will dissolve.
Correct answer: It will sink to the bottom of the container.
It will evaporate out of the container.
Q2.
A substance that dissolves in a solvent is said to be in that solvent.
Correct Answer: soluble
Q3.
Match the word with the definition.
Correct Answer:Absorb,Ability of a substance to take in another substance.

Ability of a substance to take in another substance.

Correct Answer:Solute,A substance that can dissolve in a liquid.

A substance that can dissolve in a liquid.

Correct Answer:Solvent,A liquid in which a solute dissolves.

A liquid in which a solute dissolves.

Correct Answer:Sample,A substance which will be tested in an investigation.

A substance which will be tested in an investigation.

Correct Answer:Miscible,Ability of a liquid to dissolve/mix in another liquid.

Ability of a liquid to dissolve/mix in another liquid.

Q4.
Order the following steps describing how to make a solution.
1 - If necessary, crush the solute into small pieces.
2 - Add the solute to the solvent.
3 - Stir to dissolve the solute.
4 - Filter the mixture to remove any undissolved solute.
Q5.
Oil and water are two liquids that cannot mix. They are said to be ...
An image in a quiz
Correct Answer: immiscible
Q6.
Which of the following substances are mixtures?
Correct answer: Pure orange juice
Copper sulfate
Correct answer: Ink
Oxygen
Correct answer: Tap water

Exit quiz

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6 Questions

Q1.
What is chromatography used for?
To mix coloured substances together.
Correct answer: To separate and analyse coloured mixtures.
To create coloured solutions.
Q2.
The pattern of results obtained from chromatography is called a ...
Correct Answer: chromatogram, chromatogram.
Q3.
How does a pure substance behave in chromatography?
It produces multiple spots.
It does not move.
Correct answer: It produces one spot only.
Q4.
The line on the chromatogram on which the samples are placed must be drawn in pencil because it is in the solvent.
Correct Answer: Insoluble
Q5.
Order these steps in performing chromatography, starting with drawing a pencil line.
1 - Draw a pencil line 1 cm up from the bottom of a piece of chromatography paper.
2 - Carefully add a small drop of your sample to the pencil line.
3 - Place a small volume of solvent in a beaker, lower than 1cm depth.
4 - Wind your paper on a support so that the pencil line will be above the solvent.
5 - Lower your paper vertically into the beaker so it just touches the solvent.
6 - Leave to allow the solvent to absorb up the paper and separate your sample.
7 - Remove and allow to dry.
Q6.
What can you conclude from this chromatogram?
An image in a quiz
Dye A contains three substances.
Correct answer: Dye B is insoluble in the solvent used.
Correct answer: Dye C contains only one substance.
Correct answer: Dye A is a mixture.
Dye C contains the most soluble substance.
Q6 UYSEG