NCERT Class 6 Science Chapter 5 Separation of Substances

Chapter 5 Separation of Substances

Question 1: Why do we need to separate different components of a mixture? Give two examples.
Answer: When two or more substances are mixed together they form a mixture. Components of a mixture should be separated because some components may not be useful or may spoil the useful component of the mixture.
Example: Tea leaves are separated from the liquid with a strainer, while preparing tea
                 Removal of stone pieces from wheat, rice or pulses by hand

Question 2: What is winnowing? Where is it used?
Answer: The method of separating components of a mixture is called winnowing. Winnowing is used to separate heavier and lighter components of a mixture by wind or by blowing air. This method is used by farmers to separate lighter husk particles from heavier seeds of grain.

Question 3: How will you separate husk or dirt particles from a given sample of pulses before cooking?
Answer: We can separate husk or dirt particles from a given sample of pulses before cooking by winnowing.

Question 4: What is sieving? Where is it used?
Answer: Sieving is a process by which fine particles are separated from bigger particles by using a sieve. It is used in flour mill or at construction sites. In flour mill, impurities like husks and stones are removed from wheat. Pebbles and stones are removed from sand by sieving.

Question 5: How will you separate sand and water from their mixture?
Answer: We can separate sand and water from their mixture by the process of sedimentation and decantation method. First we leave this mixture for some time. After some time, the sand which is heavier is settled down at the bottom. After that we will pour water into another container and the mixture will be separated.

Question 6: Is it possible to separate sugar mixed with wheat flour? If yes, how will you do it?
Answer: Yes, it is possible to separate sugar mixed with wheat flour by the following method. We have to mix sugar and wheat flour in water. And then we have to stir the solution to allow sugar to dissolve. Now we have to filter the mixture.

Question 7: How would you obtain clear water from a sample of muddy water?
Answer: We can obtain clear water from a sample of muddy water by allowing the muddy water to settle. And then the mud gets settled down. Finally we have to slowly pour the water to another container so that the mud particles are left in that container only.

Question 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) The method of separating seeds of paddy from its stalks is called threshing.
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 filtration.
c) Salt is obtained from seawater by the process of evaporation.
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 sedimentation & decantation.

Question 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

Question 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: Ice should be added to lemonade after dissolving sugar. It is possible to add more sugar before adding ice.