NCERT Solutions for Class 6 Science Chapter 5 Separation of Substances

Solutions of NCERT for class 6 science chapter 5 separation of substances-Exercises

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

Answer:

We see that, before we use a substance, we need to separate harmful or useless substances that may be mixed with it. Sometimes, we separate even useful components if we need to use them separately. For examples:

(a)The process that is used to separate the grain from stalks etc. is threshing .

(b) Sieving allows the fine flour particles to pass through the holes of the sieve while the bigger impurities remain on the sieve.

Question: 2 What is winnowing? Where is it used?

Answer:

This 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 commonly 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 will separate husk or dirt particles from a given sample of pulses by the handpicking method.

The handpicking method can be used for separating slightly larger sized impurities like the pieces of dirt, stone, and husk from wheat, rice or pulses.

Question: 4 What is sieving? Where is it used?

Answer:

Sieving allows the fine flour particles to pass through the holes of the sieve while the bigger impurities remain on the sieve.

In a flour mill, impurities like husk and stones are removed from wheat before grinding it 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 following steps:

• First by sedimentation, when the heavier component that is sand settles down after water is added to it.

• Then by decantation where clear water formed an upper layer is removed carefully to another glass.

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. We will follow the below steps:

• Add a lot of water to mix wheat flour and sugar both.

• Then filter this mixture using filter paper.

• On the filter paper, we have wheat flour.

• Dry it to get Wheat flour.

• The filtrate has sugar and water mixed so,

• Evaporate the water to get sugar.

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 the following steps:

• Allow the muddy water to stand for a time.

• You will see that mud settles down at the bottom.

• Upper layer water contains some mud particles.

• Decant it to get that water and filter it to remove traces of mud particles.

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 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:

We should add ice to the lemonade after dissolving the sugar as more sugar will be going to dissolve as solubility is more before adding ice. Because if we add ice before dissolving the sugar, the temperature of the water gets down and the property of dissolving the sugar will decrease.