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Explore Chromatography

In this worksheet, students will learn about chromatography as a separation technique and its uses in the identification of substances and forensics.

'Explore Chromatography' worksheet

Key stage:  KS 3

Year:  Year 8 Science worksheets

Curriculum topic:   Chemistry: Pure and Impure Substances

Curriculum subtopic:   Separating Mixtures

Difficulty level:  

Worksheet Overview

In chemistry, we refer to a pure substance as being a substance made from only one element or one compound. And nothing else.


The opposite of a pure substance is an impure substance. An impure substance is one made from more than one element or one compound, meaning it is a mixture.


Pure substances and impure substances can be identified using a simple separating technique known as chromotography.


Chromatography is a technique that is used to separate soluble substances. These are substances that are dissolved in a solvent.  For example, chromatography can be used to separate the multiple different dyes in a drop of ink, some food colouring, dyes or plant pigments.


Image of chromatography equipment


The picture below shows the chromatography results for four different inks. It's called a chromatogram. The colours they separated into can be seen by looking at the coloured dots that appear directly above the names of the different inks.




An impure substance, or a mixture, will separate into more than one spot, in a vertical column.  So you can see that the brown ink is actually made up of three colours - blue, yellow and red!


On a chromatogram, one spot means that the substance is pure. 


Think you can work out whether a substance is pure or impure by looking at chromatograms? 


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