CBSE Class 6 Science Chapter 5 Separation of Substances NCERT Solutions

CBSE Class 6 Science 

Chapter 5: Separation of Substances

NCERT Solutions

1. Why do we need to separate different components of a mixture? Give two examples.

Answer: We separate different components of a mixture, to remove the harmful and non-useful substances. It is also done to separate two useful components in a mixture. For Example, Stones are from rice or wheat is separated out from it by the method of handpicking. In construction sites, pebbles and stones are removed from sand by sieving.

2. What is winnowing? Where is it used?

Answer: Winnowing is the method of separating components by wind or by blowing air. It is commonly used by farmers to separate lighter husk particles from heavier seeds of grain.

3. How will you separate husk or dirt particles from a given sample of pulses before cooking.

Answer: We can separate the husk or dirt particles from pulses by the method of handpicking. If the husk and dirt particles are bigger in size we can used the method of sieving to separate it out

4. What is sieving? Where is it used?

Answer: Sieving is the process of removing bigger impurities by using a sieve. It is used in the construction sites to remove the stones and pebbles from sand. It is also used in floor mill, to remove bigger impurities like husks and stones from wheat before grinding it.

5. How will you separate sand and water from their mixture?

Answer: Sand and water from their mixture can be separated from their mixture, by using the method of sedimentation and decantation or filtration. Pour the sand and water mixture in  a beaker and set aside for sometime. The sand settles down in the bottom of the beaker by sedimentation. Then the water is carefully taken out from the beaker  by the process of decantation or filtration.

6. Is it possible to separate sugar mixed with wheat flour? If yes, how will you do it?

Answer: Yes. Since sugar and wheat flour are difference in size, it can be separated by sieving. Since sugar particles are bigger in size, it remains in the sieve and wheat flour passes through it.

7. How would you obtain clear water from a sample of muddy water?

Answer: We can get the clear water from the muddy water by the process of sedimentation and decantation or filtration. Pour the muddy water in a beaker and set aside for sometime. We can see that the mud settles down in the bottom of the beaker by the process of sedimentaion. Then the clear water from the top is carefully removed out by the process of decantation. It is can also be filtered out by using filter paper. 

8. Fill up the blanks

(a) The method of separating seeds of paddy  from its stalks is called ___________.
(b) When milk, cooled after boiling, is poured onto a piece of cloth the cream (malai) is left behind on it. This process of separating cream from  milk is an example of ___________.
(c) Salt is obtained from seawater by the process of ___________.
(d) 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 ___________.

Answer:

(a) Threshing
(b) filtration
(c) evaporation
(d) sedimentation and decantation

9. True or false?

(a) A mixture of milk and water can be separated by filtration.
(b) A mixture of powdered salt and sugar can be separated by the process of winnowing.

(c) Separation of sugar from tea can be done with filtration.

(d) Grain and husk can be separated with the process of decantation.

Answer:

(a) False
(b) False
(c) False
(d) False

10. Lemonade is prepared by mixing lemon juice and sugar in water. You wish to add ice to cool it. Should you add ice to the lemonade before or after dissolving sugar? In which case would it be possible to dissolve more sugar?

Answer: We should add the ice after dissolving sugar. More sugar can be dissolved, if we add it before adding ice, since the ability of a liquid to dissolve a substance is more when the temperature is more.