Class 6 Science Chapter 9 Extra Questions and Answers Methods of Separation in Everyday Life
NCERT Class 6 Science Chapter 9 Methods of Separation in Everyday Life Important Extra Questions and Answers
Question 1.
When is handpicking used?
Answer:
Handpicking is used to separate undesirable component, when present in small amount.
Question 2.
What is threshing? How is it done?
Answer:
The process that is used to separate the grain from stalks is threshing. In this process, the stalks are beaten to free the grain seeds. Sometimes, threshing is done with the help of bullocks. Machines are also used to thresh large quantities of grain.
Question 3.
Give one example of sieving used in everyday life.
Answer:
Separation of barn (choker) from flour.
Question 4.
Name some materials that are used as filters.
Answer:
Cotton, filter cloth, filter paper.
Question 5.
What is the use of decantation?
Answer:
Decantation is used to separate insoluble solids from liquids. Two immiscible liquids are also separated by this process.
Question 6.
What is the drawback of evaporation?
Answer:
The liquid in the mixture is evaporated off into the air and is not recovered.
Question 7.
Name the process to obtain salt from seawater.
Answer:
Evaporation.
Question 8.
What is decantation?
Answer:
Decantation is a process of separating insoluble solids from liquids. A suspension of solid particles in liquid is allowed to stand for some time. Solid particles settle down at the bottom, due to their weight. This is called sedimentation. The clean water is transferred into another beaker, without disturbing the settled particles. This type of separation is called decantation (Fig.).
Question 9.
Which types of mixtures are separated by evaporation?
Answer:
Evaporation is used to separate solids dissolved in liquid.
Question 10.
Describe the method to obtain pure salt from rock salt.
Answer:
First, the mixture is crushed and grinded. Water is then added and filtered. Pure salt is collected as filtrate which is heated for evaporation. Water evaporates off and pure salt is left.
Question 11.
What is the importance of centrifugation? How is it done?
Answer:
Centrifugation is the process of separating suspended particles from a liquid by rotating the liquid at a high speed.
The mixture is taken in a closed bottle and rotated at a high speed. The heavy particles settle at the bottom while light particles remain behind. This method is also used to separate cream from milk. Cream collects at the centre and being lighter than milk, it floats at the- top of the mixture.
Question 12.
Name the property of the components used for separating the following mixtures:
1. salt and water
2. wheat and husk m iron fillings and saw-dust
3. iron filling and saw-dust
Answer:
- evaporation
- winnowing
- magnetic separation
Question 13.
Write various methods of separation of compounds from their mixture.
Answer:
- Handpicking
- Threshing
- Winnowing
- Sedimentation
- Decantation
- Evaporation
- Condensation.
Question 14.
Name and describe briefly a method which can be helpful in separating a mixture of husk from grains. What is the principle of this method?
Answer:
Winnowing: Winnowing can be used to separate lighter and heavier components of a mixture. Wheat grains and husk are different in weight, husk is lighter than wheat. When the mixture is allowed to fall down from a height, the wind carries the lighter husk with it and the heavy wheat grains fall vertically down on the groqnd.
Principle of this method is that the lighter particles are carried away by the wind.
Question 15.
How will you separate pure water from a solution of salt in water?
Answer:
We can separate pure water from a solution of salt in water, by the process of distillation that is by evaporation and followed by condensation.
Question 16.
Write opposite process of condensation.
Answer:
Evaporation.
Question 17.
How is common salt obtained from seawater?
Answer:
When seawater is allowed to evaporate in shallow pits, water gets heated by sunlight and changes into water vapour by the process of evaporation leaving behind impure solid salts. Now, the lumps of impure common salt are crushed to get powdered salt. The powdered common salt is dissolved in water to prepare a solution. Now the solution of common salt is filtered to remove insoluble impurities. The clear solution is evaporated by heating to remove the water content to obtain a concentrated solution of common salt. The hot and concentrated solution is allowed to cool. On cooling, crystallization takes place and crystals of pure common salt are obtained.
Question 18.
During centrifugation, which particles settle down at the bottom?
Answer:
Heavy particles settle down at the bottom and lighter particles float at the top of the liquid.
Question 19.
Name the method by which you can separate butter from milk.
Answer:
Centrifugation.
Question 20.
Name the device by which cream can be separated from milk at home.
Answer:
A mixer-grinder is the very important device by which cream can be separated from milk by the process of centrifugation. (Fig.)
Question 21.
Mention the methods that can be used for the separation of the following mixtures:
(i) wheat, sugar and husk
(ii) rice, gram and iron fillings
(iii) sand, black gram (urad) and husk.
Answer:
-
Mixture of wheat, sugar and husk.
- For separating husk from the mixture, we should follow the winnowing method as husk is lighter than other two components.
- Wheat and sugar can be separated by sieving as they have different sizes.
-
Mixture of rice, gram and iron fillings.
- For separating iron fillings, we can use a magnet.
- Rice and gram can be separated either by sieving or by handpicking.
-
Mixture of sand, black gram (urad) and husk.
- For separating sand from the mixture, we can sieve the mixture.
- Black gram (urad)and husk can be separated by the method of winnowing.
