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It is important for chemists to be able to separate mixtures.
Why? Well we may need some of the nitrogen out of the air for example.
In this section you will learn some of the separating methods used by chemists.
Filtration
Filtration
Filtration is used to separate an insoluble solid from a liquid.
The equipment needed for filtration is shown in the diagram:
An example of separating mixtures - Rock salt
An example of separating mixtures - Rock salt
Rock salt is a mixture of sand and salt. To separate rock salt you need to carry out the following steps:
Grind up the salt and sand mixture using a mortar and pestle
Add water to dissolve the soluble salt
Filter the mixture. The sand will be left in the filter paper
The salt dissolved in water will pass through the filter paper
The dry salt can then be obtained by evaporating the water
The video below shows an experiment where a ground up mixture of salt can be separated from sand by using filtration. The salt can be obtained by evaporation.
Chromatography
Chromatography
Inks are mixtures of a liquid solvent, which is often water or alcohol and a colouring substance.
This experiment is a way of finding out which substances are in a mixture.
This method used to separate out the dyes in the inks is called chromatography.
The video below shows chromatography using a slection of different inks. It is for illustration purposes and you only need to know how the method works (up to around 1:30 in the video) and not the information about Rf values.
Distillation
Distillation
Distillation is a method of separating mixture of liquids by their different boiling points.
Distillation involves evaporation followed by condensation.
The video below shows what the process of distillation looks like in a laboratory.
Distillation is used industry to separate alcohol from water in the making of whisky. This is due to the water having a boiling point of 100oC and alcohol having a boiling point of 78oC.
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