Solutions for Separation of Substances Class 6

The chapter “Separation of Substances” in BOSEM Class 6 Science teaches students about different methods used to separate mixtures into their components. It explains why separating substances is important in everyday life and introduces various techniques such as handpicking, sieving, filtration, evaporation, and decantation. Through this chapter, students will understand how different materials are separated based on their physical properties, such as size, solubility, and density. The chapter also provides practical examples of separation methods used in households and industries.

Learning Objectives:

Important Terms and Definitions For Separation of Substances

1. Mixture: A combination of two or more substances that are physically mixed but not chemically combined.
2. Handpicking: A method of separation where large and easily distinguishable particles are manually removed from a mixture.
3. Sieving: A method used to separate particles of different sizes by passing them through a sieve or mesh.
4. Filtration: A process that separates insoluble solids from liquids using a filter.
5. Evaporation: The process of separating a dissolved solid from a liquid by heating the mixture until the liquid evaporates, leaving the solid behind.
6. Decantation: The process of separating liquids from solids or immiscible liquids by carefully pouring off the liquid from the top, leaving the solid or heavier liquid behind.
7. Sedimentation: A process where heavier solid particles settle down at the bottom of a liquid mixture, making separation easier.
8. Condensation: The conversion of a gas or vapour into a liquid, often used in conjunction with evaporation for separating liquids.
9. Solution: A homogeneous mixture where a solute is dissolved in a solvent.
10. Soluble: A substance that can dissolve in a liquid, such as sugar in water.
11. Insoluble: A substance that does not dissolve in a liquid, like sand in water.

Solutions for Separation of Substances

Q1. Why do we need to separate different components of a mixture? Give two examples.
Ans: We need to separate different components of a mixture because of the following reasons:

1. To separate two different, but useful components.
2. To remove non-useful components.
3. To remove impurities of harmful components.

Examples: Separating stones from rice and Churning milk to obtain butter.

Q2. What is winnowing? Where is it used?
Ans: Winnowing is the process used to separate heavier and lighter components of a mixture by wind or by blowing air.

This process is used by farmers to separate the lighter husks from heavier seeds of grains.

Q3. How will you separate husk or dirt particles from a given sample of the pulses before cooking?
Ans: Husks or dirt particles from a given sample of the pulses are separated by hand-picking before cooking.

Q4. What is sieving? Where is it used?
Ans: Sieving is a process by which fine particles are separated from bigger particles by using a sieve.
It is used in flour mills or construction sites.

Q5. How will you separate sand and water from their mixture?
Ans: Sand is separated from water by the process of sedimentation and decantation methods. First, we leave this mixture at rest for some time. The heavier sand settled down at the bottom. After that, we will pour water into another container and the mixture will be separated.

Q6. Is it possible to separate sugar mixed with wheat flour? If yes, how will you do it?
Ans: Yes, it is possible to separate sugar mixed with wheat flour.
Sugar can be separated from wheat flour by the method of sieving. Due to the difference in the sizes of the particles, sugar will remain on the sieve and the fine wheat flour will pass through the holes of the sieve.

Q7. How will you obtain clear water from a sample of muddy water?
Ans: We can obtain clear water from a sample of muddy water by the process of filtration. In this method, a filter paper folded in the form of a cone is fixed on the funnel. The mixture is then poured onto the filter paper. Solid particles, that is the mud particles will remain on the filter paper whereas clear water will pass through it.

Q8. Lemonade is prepared by mixing lemon juice and sugar in water. You wish to add ice to cool it. Should you add ice to lemonade before or after dissolving sugar? In which case would it be possible to dissolve more sugar?
Ans: We should add ice only after dissolving sugar in lemonade because more sugar can be dissolved at high temperatures. After mixing with ice, it gets cooled which enables it to dissolve less sugar in it.

Fill in the blanks

1. The method of separating the seeds of paddy from its stalks is called threshing.
2. When milk, cooled after boiling, is poured into a piece of cloth, the cream is left behind on it. The process of separating cream from milk is an example of filtration.
3. Salt is obtained from seawater by the process of evaporation.
4. Impurities settled at the bottom when muddy water was kept overnight in a bucket. The clear water was then poured off from the top. The process of separation used in this example is called Decantation.

State True or false

1. A mixture of milk and water can be separated by filtration (False)
2. A mixture of powdered salt and sugar can be separated by the process of winnowing. (False)
3. Separation of sugar from tea can be done with filtration (False)
4. Grain and husk can be separated with the process of decantation. (False)

Extra Questions and Answers for Separation of Substances

Q1. Name any four methods used for the separation of substances.
Ans: Winnowing, hand picking, sieving and filtration.

Q2. Define the following
1. Threshing
2. Decantation
3. Evaporation.
4. Condensation

Ans:

1. Threshing: The method used to separate grain from stalks by beating is called threshing.
2. Decantation: The process in which water is removed when heavier components in a mixture settle at the bottom is called decantation.
3. Evaporation: The process of conversion of water into its vapour is called evaporation.
4. Condensation: The process of conversion of water vapour into its liquid form is called condensation.

Q3. How is threshing done by farmers?
Ans: Threshing is done by farmers in the following ways:

1. By beating the stalk
2. With the help of bullocks
3. By using machined.

Q4. How is salt prepared from seawater?
Ans: Salt is prepared from seawater by evaporation and condensation. Sea water is collected in a shallow pit and allowed to evaporate. After the evaporation of water, crystals of salts are obtained. Common salt is obtained from this mixture of salts by further purification.

Q5. What kind of substance can be separated by sieving, hand-picking and decantation?
Ans:

Q6. Which property can affect the dissolution of substances in water?
Ans: Temperature.

Separation of Substances Notes

1. Substances which contain more than one component mixed in any ratio are called mixtures.

2. Handpicking is the process by which the unwanted particles are just picked up by hand. Slightly large size impurities can be separated by the method of handpicking. For example, pieces of dirt, stone and husk from wheat, rice or pulses are separated by this method.

3. Threshing is the process of separating grains from stalk. This process is done by beating the grain seeds, sometimes with the help of bullocks. Nowadays machines are also used.

4. Winnowing is the process of separating heavier and lighter components of a mixture by wind or by blowing air. This method is commonly used by farmers.

5. Sedimentation is the process of settling down od heavier components from a mixture. Example: A mixture of sand and water.

6. Decantation is the process of transferring clean liquid without disturbing the sediments.