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Separation of Substances

There are two kinds of substances:
 Soluble substances
 Insoluble substances
Soluble substances are those that dissolve completely in water like salt and sugar.
Insoluble substances are those that do not dissolve completely in water like sand and
chalk.
There are many ways by which we can separate substances from a solution. Let’s learn
about some of them.
Take a salt solution and heat it. On heating the water vanishes through water vapours
and the salt particles are left behind. Hence, to separate soluble substances we can
heat them.
Insoluble substances cannot be separated by heating. They can be separated by three
processes – filtration, sedimentation and decantation. You will learn about these
methods in higher classes in detail.

The solution is passed through filter paper to separate insoluble substances by
filtration. In sedimentation and decantation the solution is left undisturbed for some
time. The solute settles down and then the solvent is poured into another container.

Let’s
Revise

 Matter is all around us. It is the stuff you touch and see.
 Matter is defined as anything that has mass and takes up space.
 Solids are substances which the particles are packed very close to each other.
 Liquids are substances in which the particles are not very closely packed.
 Gases are substances in which particles are very loosely packed.
 Materials can be changed from one state to another by heating or cooling.
 Soluble substances are those that dissolve completely in water like salt and sugar.
 Insoluble substances are those that do not dissolve completely in water like sand and chalk.

Points to Remember

Matter : everything around us.
Solute : The solid that dissolves in water
Solvent : The liquid in which we dissolve the solid

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