Exercises
1. Why do we need to separate different components of a mixture? Give two examples.
2 What is winnowing? Where is it used?
3. How will you separate husk or dirt particles from a given sample of pulses before cooking.
4. What is sieving? Where is it used?
5. How will you separate sand and water from their mixture?
6. Is it possible to separate sugar mixed with wheat flour? If yes, how will you do it?
7. How would you obtain clear water from a sample of muddy water?
Answers
Answer :
1. We need to separate different components of a mixture to obtain the pure components of the mixture.This is also needed to obtain USEFUL substances from the USELESS(or sometimes harmful) substances .
Examples :
Tea Leaves are separated from tea.
Pebbles and stones are handpicked from rice and pulses .
2. Winnowing: The process of separating heavier and lighter components of a mixture by wind or by blowing air is called winnowing.
This method is used by farmers to separate lighter husk particles from heavier seeds of grain.
3. Husk or dirt particles can be separated by winnowing method. It is used to separate the heavier and lighter components of a mixture by wind or by blowing air.
In this method, the mixture of husk and seeds of grain are take in plate and are made to fall down from a height up to our shoulders. As the mixture falls down, lighter husk is taken away by blowing air and the heavier grain seeds fall down to make a heap.
4. The process of separating fine particles from the larger particles by using a sieve, is called sieving.
This method is used in a flour mill where impurities like husk and stones are removed from wheat before grinding it.
This method is also used at our homes where fine flour particles are separated from bigger impurities by using a sieve.
5. Sand and water can be separated by any of the following two methods:
(a) Sedimentation and decantation: Mixture is kept undisturbed for some time. After some time, sand being heavier and insoluble in water, settles down at the bottom of container. Now, water is poured into another container to separate it from sand.
(b) Filtration: Mixture of sand and water is passed through a filter paper (a filter with very fine pores). Sand particles being larger in size are retained by the filter paper and get separated from water.
6. Sugar can be separated from wheat flour by sieving. Sugar particles being larger in size are retained by the sieve whereas wheat flour will pass through it.
7. We can obtain clear water from a sample of muddy water by the process of filtration.
In this method, we use a filter paper that is fixed in the funnel. Then the mixture is poured on the filter paper. Mud particles being larger in size will remain on the filter paper whereas clear water will pass through it.