NCERT Class VI
Lesson 5:Separation of Substances.
1.Question.Why do we need to separate different components of a mixture> Give two examples.
Answer. When two or substances are mixed together, we call it a mixture. Sometimes, different components of a mixture are not useful or may even harmful. So, we need to separate different components of the mixture.
(1) After preparing tea, the tea leaves are not useful.
(2) Small stones present in rice are harmful.So, we need to separate them.
2.Question. What is winnowing? Where id it used?
Answer. (1) Winnowing is used to separate heavier and lighter components of a mixture by wind by blowing air.
(2) This method is commonly used by farmers to separate lighter husk particles from heavier seeds of grain.
3.Question.How will you separate husk a dirt particles from a given sample of pulses before cooking?
Answer.(1) This can be done by handpicking.
(2) The method of handpicking is normally used for separating slightly larger size impurities like piece of dirt, stone, husk from wtheat, rice or pulses.
4.Question. What is sieving? Where it is used?
Answer. (i) Sieving allows fine particles to pass thourgh the holes of thesieve, while the bigger impurities remain on the sieve.
(ii) In a flour mill, impurities husk and stones are removed from wheat by sieving.
5.Question. How will you sand and water from their mixture?
Answer.(1) Allow mixture to sand in a glass.
(2) Sand settles at the bottom (sedimentation)
(3) Clear water froms at the upper layer.
(4) Gently pour this water in another glass (decantation)
6.Question. Is the possible to separate sugar mixed with wheat flour? if yes, how will you do it?
(1) Mix sugar and wheat mixture in lot of water.
(2) Filter it.
(3) On the filtr paper in wheat.
(4) Dry to get wheat flour.
(5) Filter is a sugar-water mixture.
(6) Evaporota this to get sugar.
(a) Making solution.
7.Question.How would youobtain clear water from a sample of muddy water?
Answer.(1) Allow muddy water to stand.
(2) Mud settles at the bottom(sedimentation)
(4) Decant it.
(5) Upper layer is clear water.
(6) Then filter this water again to remove traces of mud particles
8.Question. Fill up the blanks.
(a) The method of separating seeds of paddy its stalks is called * threshing*.
(b) When milk, cooled after boiling, is poured on to 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*.
8. Question. True or False?
(a) A mixture milk and water can be separated by filtration.(F)
(b) A mixture of powdered salt and sugar can be separate by the process of winnowing.(F)
(c) Separation of sugar from tea can be done filtration.(F)
(d) Grain and husk can be separated with the process of decantation.(F)
10.Question. 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. (1) We should add ice to the lemonade after dissolving sugar.
(2) It will be possible to dissolve more sugar before adding ice.