Distillation is a separation technique that 14–16 students should be familiar with for separating two miscible liquids with sufficiently different boiling points

Specifications suggest a range of mixtures that could be separated using this technique, including orange juice, cherry cola or inks.

Equipment and set up

This video resource from our interactive lab primer collection gives a quick introduction to each of the pieces of equipment and their purpose in the distillation procedure. The set up uses a heating mantle rather than a bunsen burner, which may not be available in most school laboratories.

Separation of a water soluble dye

This resource from CenturyTech uses animation to illustrate the equipment involved and gives advice on how to conduct the practical. It describes separation of a water soluble dye, which is the closest to the recommendations in the Edexcel and OCR specifications. The animation states that all the liquid will eventually be evaporated leaving a concentrated dye. In practise you would not want to do this with school laboratory apparatus as issues will arise with significantly hotter glassware and permanent staining of equipment.

Separation of water and acetone

This video from MeitY OLabs, by Amrita University, shows the equipment set up and in use with water and acetone. Although both are clear liquids, acetone has a lower boiling point than water so you can see that a liquid is separated at 54°C rather than at 100°C. Some differences from the familiar school laboratory set up should be highlighted if you share this video with learners, again the heat source is a heating mantle, whereas typically learners will see the demonstration of simple distillation using a bunsen flame.

Separation of salt water

This video by Findel Education on Vimeo is produced in association with an equipment manufacturer, so does contain some advertising in the opening remarks. The set up is correct and the presenter uses the correct terminology, including naming the ‘Liebig condenser’ (expected in the AQA GCSE specification). The apparatus is used to separate salty water leaving sodium chloride as a dry solid. There is a good demonstration of using appropriate tests for sodium and chloride ions before and after the distillation to show that the distillate is different from the original mixture. There is a minor error in the video where the presenter incorrectly refers to a chloride ion as a ‘cation’ rather than an anion. Additionally, the separation does result in allowing the round bottom flask to boil dry – something that would not be recommended in a classroom laboratory and could result in permanent damage to expensive equipment. 

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Separation of a carbonated drink

Follow this link to Cambridge Assessment International Education for a video showing the distillation of a carbonated drink using a different set up. This distillation does not use a condenser, but instead uses ice baths to condense the separated substances. The video also considers the gases that are separated by testing for carbon dioxide using limewater.

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