1. Pure substances : Many substances around us contain only one type of constituent particles. Elements and compounds are pure substances. These are called pure substances. For example, iron, copper, water, salt, etc.
2. Impure substances :Substances containing more than one type of constituent particles are called impure substances for example, pond water, milk, etc.
3. Impurities : These are the unwanted particles present in a substance making it impure.
4. Mixtures :Substances which contain more than one component mixed in any ratio are called mixtures. For examples : air is a mixture of many gases like Nitrogen, Oxygen, Carbon dioxide and dust particles, etc.
5. Homogeneous mixtures :Mixture in which the particles of the substance present cannot be seen are called homogeneous mixtures. For example, solution of sugar and water, air, cold drinks.
6. Heterogeneous mixtures : Mixture in which particles of the substances present can be seen easily are called heterogeneous mixtures. For example, water in oil, dust in air.
7. Solution : When a soluble substance is dissolved completely in a liquid (say sugar in water). A homogeneous mixture is formed. It is known as solution.
8. Saturated solution : A solution in which no more soluble substance can be dissolved at room temperature is called saturated solution.
9. Need for separation : We carry out the separation of the components of a mixture or an impure substance with the following purposes :
(i) To remove the unuseful or harmful component.
(ii) To obtain the useful component.
(iii) To remove impurities for getting a pure sample.
10.Principle of separation
1. The substances present in a mixture retain their original properties like particle size, density, melting point, boiling point, volatility, etc.
2. We use the difference in anyone of these properties in the components of a mixture to separate them.
11.Methods of separation : Hand picking, winnowing, sieving, magnetic separation, sedimentation, decantation, loading, filtration, evaporation, sublimation, distillation, churning, etc. are some common methods of separation.
12.Handpicking :This method is used for separating small particles of dirt, stone, husk etc. from the grains of wheat, rice, pulses, etc.
13.Sieving
(i) Sieving is used when two component of a mixture have different particle size.
(ii) Sieving allows the fine particles to pass through the holes of the sieve, while the bigger particles remain on the sieve. For examples, sieving of wheat flour, sieving of sand at construction sites.
14.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.
15.Threshing : The process that is used to separate grain from stalks is threshing.
16.Decantation :It is the transfer of clean liquid from one vessel to other vessel without disturbing the settled (sedimented) particles.
17.Loading : It is the process of faster sedimentation by suspending alum to a liquid.
18.Filtration :Filtration is used to separate solid particles from liquid by passing the mixture through a filter paper.
19.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.
20.Condensation :The process of conversion of water vapour into its liquid form is called condensation.
21.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.
22.Crystallisation :The process of crystallization is used for obtaining pure crystallive substance from impure sample.
23.Sedimentation :It is the process of settling of heavy solid particles in a mixture at the bottom of the vessel.
Answers & Comments
Answer:
1. Pure substances : Many substances around us contain only one type of constituent particles. Elements and compounds are pure substances. These are called pure substances. For example, iron, copper, water, salt, etc.
2. Impure substances :Substances containing more than one type of constituent particles are called impure substances for example, pond water, milk, etc.
3. Impurities : These are the unwanted particles present in a substance making it impure.
4. Mixtures :Substances which contain more than one component mixed in any ratio are called mixtures. For examples : air is a mixture of many gases like Nitrogen, Oxygen, Carbon dioxide and dust particles, etc.
5. Homogeneous mixtures :Mixture in which the particles of the substance present cannot be seen are called homogeneous mixtures. For example, solution of sugar and water, air, cold drinks.
6. Heterogeneous mixtures : Mixture in which particles of the substances present can be seen easily are called heterogeneous mixtures. For example, water in oil, dust in air.
7. Solution : When a soluble substance is dissolved completely in a liquid (say sugar in water). A homogeneous mixture is formed. It is known as solution.
8. Saturated solution : A solution in which no more soluble substance can be dissolved at room temperature is called saturated solution.
9. Need for separation : We carry out the separation of the components of a mixture or an impure substance with the following purposes :
(i) To remove the unuseful or harmful component.
(ii) To obtain the useful component.
(iii) To remove impurities for getting a pure sample.
10.Principle of separation
1. The substances present in a mixture retain their original properties like particle size, density, melting point, boiling point, volatility, etc.
2. We use the difference in anyone of these properties in the components of a mixture to separate them.
11.Methods of separation : Hand picking, winnowing, sieving, magnetic separation, sedimentation, decantation, loading, filtration, evaporation, sublimation, distillation, churning, etc. are some common methods of separation.
12.Handpicking :This method is used for separating small particles of dirt, stone, husk etc. from the grains of wheat, rice, pulses, etc.
13.Sieving
(i) Sieving is used when two component of a mixture have different particle size.
(ii) Sieving allows the fine particles to pass through the holes of the sieve, while the bigger particles remain on the sieve. For examples, sieving of wheat flour, sieving of sand at construction sites.
14.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.
15.Threshing : The process that is used to separate grain from stalks is threshing.
16.Decantation :It is the transfer of clean liquid from one vessel to other vessel without disturbing the settled (sedimented) particles.
17.Loading : It is the process of faster sedimentation by suspending alum to a liquid.
18.Filtration :Filtration is used to separate solid particles from liquid by passing the mixture through a filter paper.
19.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.
20.Condensation :The process of conversion of water vapour into its liquid form is called condensation.
21.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.
22.Crystallisation :The process of crystallization is used for obtaining pure crystallive substance from impure sample.
23.Sedimentation :It is the process of settling of heavy solid particles in a mixture at the bottom of the vessel.
Explanation: