Separation Of Substances CBSE Class 6 Notes | DailyHomeStudy

Written by on May 15, 2021 in Notes

Pure Substances Many substances around us contain only one type of constituent particles. Elements and compounds are pure substances. Some of the pure substances are iron, copper, water, salt, etc.

Impure Substances Substances containing more than one type of constituent particles are called impure substances. Some of the impure substances are pond water, milk, etc

Impurities These are the unwanted particles present in a substance making it impure.

Mixtures Substances which contain more than one component mixed in any ratio are called mixtures. For example, air is a mixture of many gases like nitrogen, oxygen, carbon dioxide, dust particles, etc.

Homogeneous Mixtures The mixtures in which the particles of the substances present cannot be seen are called homogeneous mixtures. For example, solution of sugar and water, air, cold drinks, etc.

Heterogeneous Mixtures The mixtures in which particles of the substances present can be seen easily are called heterogeneous mixtures. For example, water in oil, dust in air.

Need for Separation We carry out the separation of the components of a mixture or an impure substance with the following purposes:

Principle of separation

Methods of Separation Handpicking, winnowing, sieving, magnetic separation, sedimentation, decantation, loading, filtration, evaporation, sublimation, distillation, churning, etc., are some common methods of separation.

Churning (or Centrifugation) It is the process of separation of the lighter particles of a suspended solid from a liquid. For example, to obtain butter from the curd or milk.

Condensation The process of conversion of water vapour into its liquid form is called condensation.

Crystallisation The process of crystallisation is used for obtaining pure crystalline substance from impure sample.

Decantation It is the transfer of clean liquid from one vessel to the other without disturbing the settled (sedimented) particles.

Evaporation It is the process of removing water (or moisture) from a mixture either by heating on flame or direct sunlight. For example, salt from sea water is obtained by this method.

Filtration Filtration is used to separate solid particles from liquid by passing the mixture through a filter paper.

Handpicking This method is used for separating small particles of dirt, stone, husk, etc., from the grains of wheat, rice, pulses, etc.

Loading It is the process of faster sedimentation by suspending alum to a liquid.

Sedimentation It is the process of settling of heavy solid particles in a mixture at the bottom of the vessel.


Saturated solution A solution in which no more soluble substance can be dissolved at room temperature is called saturated solution.

Solution When a soluble substance is dissolved completely in a liquid (say sugar in water), a homogeneous mixture is formed. It is known as a solution

Threshing The process that is used to separate grain from stalks is threshing.

Winnowing Winnowing can be used to separate lighter and heavier components of a mixture. For example, to separate husk from grain with the help of air.

Methods Of Separation

Different methods are used for separating different substances that are mixed together. Let us learn about some common methods that are used.



Hand-picking Rice, wheat, pulses, etc., that we buy from the market may contain impurities (unwanted or harmful particles) in the form of small stones, unwanted grains, etc. Often, these impurities look very different from the food item and can be spotted easily. The method of separation used in such a case is hand-picking (Fig. 3.4). This method is preferred when


Sedimentation and Decantation



Solution And Solubility


Threshing The process of beating harvested crops to separate seeds from the stalks is called threshing.

Winnowing The method used to separate chaff from the grain by wind or blowing air is called winnowing.

Sedimentation The process of separating insoluble solids suspended in a liquid by allowing them to settle down is called sedimentation.

Decantation The process of pouring out the clear upper liquid without disturbing the sediments is called decantation.

Filtration The process by which an insoluble solid is separated from a liquid by passing the mixture through a filtering device is called filtration.

Saturated solution A solution that can dissolve no more of the solute is called a saturated solution.

Threshing is done either manually or by using machines to separate seeds or grains from the stalks.

Winnowing involves separating the chaff from the grain by letting the mixture fall to the ground from a height when the wind is blowing.

Hand-picking involves manually removing small stones, insects, etc. from the grains.

Sedimentation and decantation are used to separate an insoluble solid from a liquid.

Insoluble solid impurities present in water can be removed by filtration.

Common salt can be separated from seawater by evaporation.

Solubility of a solute can be increased by heating the mixture or it can also be increased by adding the solute in the powdered form.

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