One major activity in chemistry is the analysis of materials in our environment. Many materials found in our environment are mixtures, and we often want to separate the constituents of a mixture. In chemistry, the separation of constituents of mixtures involves the application of simple principles and use of special pieces of apparatus. This process of separating mixtures into it component part is known as 'separation technique'. Pure substances can also be obtaned from impurities by using various methods of separation techniques.
There are different types of mixtures:
- Mixture of a solid and liquid e.g. precipitates.
- Mixture of a liquid and gas e.g. carbonated drinks.
- Mixture of a solid and solid e.g steel
- Mixture of a gas and gas e.g. air
The methods and principles which are applied in the separation of mixtures in chemistry are based on the special properties of the constituents of the mixtures. Such properties like different boiling points, different densities, different solubilities are frequently used.
Methods of separating mixtures
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These methods are used to separate different kinds of mixtures which are explained in full details below.
1. Separating solids from liquids
Filtering involves the process of pouring the mixture into a porous material, e.g filter paper. During filtration, the liquid portion passes through the filter paper while the solid material remains on the paper. The liquid which passes through the filter paper is called the filtrate while the portion which remains on the filter paper is called the residue.
For example, chalk is insoluble in water. So it is easy to separate by filtering.The chalk is trapped in the filter paper, while the water passes through.The trapped chalk particles is the residue. The water is the filtrate.
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2 By crystallisation
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