C1: Filtration



In chemistry, there are many different methods of separating materials from each other. To separate the elements in a compound from each other, a chemical reaction is required.

A mixture can be separated by physical processes and this is what we are going to be looking at today.

The five main processes which you can be asked about in the exam are filtration, evaporation, simple distillation, fractional distillation, and chromatography.

Let’s start with filtration.

Filtration can be used when you have something which is insoluble, that means it does not dissolve, in a liquid.

A filter is used to separate the solid and the liquid from each other because the solid cannot fit through the holes in a filter, but the liquid can.

The most common filter used in GCSE science lessons is filter paper. The filter paper is placed in a funnel on top of a collection vessel and the mixture is poured through. The insoluble solid remains on the filter paper but the liquid passes through.


Filtration can be used to separate sand from water.  If you had salt water and sand, the sand would remain in the filter, but the salt would pass through.

This is because the salt ions, formed when the salt is added to the water, are smaller than the holes in the filter. If you wanted to extract either the salt or the water from your salt water mixture, you would need a second separation technique.