One feature of mixtures is that they can be easily separated into their component parts.
Here we'll look at four of the physical methods available for this separation.
Select each method to find out more
Crystallisation
When salt dissolves in water, the resulting mixture is called a solution. To separate this mixture, you can apply heat, so that some of the water evaporates, then allow the solution to cool.
As it cools, the salt will separate from the water to form solid crystals.
Filtration
Suppose you want to separate a mixture of sand and salt. You can do this by adding water. The salt will dissolve, but the sand will not.
When you pour the result through a filter, the sand, but not the salt, will be trapped on the filter paper.
Distillation
Crystallisation lets us collect solids from a solution. But, sometimes we want to collect the liquid. Distillation lets us do this.
When we heat a salt solution, we don't let the evaporating water escape. Instead, we pass it down a tube to cool and collect the liquid water in a flask.
Chromatography
Different coloured dyes in a liquid can be separated using a specially treated chromatography card.
The liquid seeps up the card, carrying the dye mixture. Each dye stops at a different place on the card. The results can then be compared to a reference card, allowing the dyes to be identified.
