An introduction to separating mixtures. Salt is soluble in water, so when salt is added to water most of it dissolves to make a solution. When sand is added to water it either hangs in the water or forms a layer at the bottom of the container. Sand therefore does not dissolve in water and is insoluble. It is easy to separate sand and water by filtering the mixture. Salt can be separated from a solution through evaporation. The water can also be recovered if the water vapour is trapped and cooled to condense the water vapour back into a liquid. This process is called distillation.

First broadcast:
11 October 2007

Students could recreate the experiments presented in this clip to witness filtration and distillation first-hand. Students could first separate sand and water using a simple paper filter, then go on to separate the remaining salt and water solution with a Bunsen burner. The water vapour could be collected using a tube and beaker.

This clip is useful as a way of introducing the students to scientific vocabulary including soluble, insoluble, evaporation, filtration and distillation through the use of visual explanations. Students could draw diagrams of the three experiments and annotate their drawings with this vocabulary.