NCERT Solutions for Class 6 Science Chapter 5 Separation Of Substances

Q1 ) Why do we need to separate different components of a mixture? Give two examples.

Answer :

When two or more substance mix together we call it a mixture. Separating the mixture is necessary because the substance added to it is sometimes unuseful or undesirable. Therefore, it would be necessary to separate the mixture to obtain the pure substance.

Example:
(a) Stone pieces from wheat, rice or pulses are picked out by hand.

(b) Sand mixed in water is separated by sedimentation.

Q2 ) What is winnowing? Where is it used?

Answer :

It is the mathode of separating. When the heavier components are separated from the lighter by the wind or blowing air, it is called winnowing.

This method is used to separate grains from the husk.

Q3 ) How will you separate husk or dirt particles from a given sample of pulses before cooking?

Answer :

Separate husk or dust particles from pulses before cooking by hand picking or winnowing. Undesirable substances such as piece of stone in the pulse or rice can be separated by hand-picking but husk is mixed with the pulse then we separate it by winnowing.

Q4 ) What is sieving? Where is it used?

Answer :

When the constituents of a mixture have particles of different sizes, sieve is used to separate them. The size of the pore in the sieve depends on the size of the particles of the constituents to be separated. When an object separated by sieve then this process of separation is called sieving.
It is used to move husk from flour.

Q5 ) How will you separate sand and water from their mixture?

Answer :

We will allow the mixture of water and sand to stand for some time in a pot. When the sand settles down in the bottom of pot, carefully we pour the water into another pot with the help of glass rod, thus separating the mixture. This process is called sedimentation so, we will separate sand and water from their mixture by the process of sedimentation.

Q6 ) 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 sieving method. Since the particle of sugar is larger than the particle of flour then sugar is stay on sieve and flour is separated from mixture.

Q7 ) How would you obtain clear water from a sample of muddy water?

Answer :

We obtain clear water from a sample of muddy water by sedimentation or decantation method.

1. Leave the muddy water for some time. And after some time, take a circular piece of filter paper and fold it. And make a cone.
2. Place the filter paper cone in a funnel.
3. Keep a beaker below that funnel.
4. Pour the muddy water slowly into a cone, using a glass rod clear water flows down the funnel and collects in the beaker below.
5. Take out the filter paper cone and open it out.Mud particles are seen on the paper.

Q8 ) 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 $decantation$ .

Q9 ) 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) A mixture of milk and water can be separated by filtration.$?$ false
No, A mixture of milk and water can not be separated by filtration because milk is soluble in water.

(b) A mixture of powdered salt and sugar can be separated by the process of winnowing. $?$ false
No, A mixture of powdered salt and sugar can not be separated by the process of winnowing. Because the weight of both be same.

(c) Separation of sugar from tea can be done with filtration. $?$ false
No, separation of sugar from tea can not be done with filtration because sugar is soluble in water.

(d) Grain and husk can be separated with the process of decantation. $?$ No, Grain and husk can not be separated with the process of decantation. Because it is separated by the winnowing.

Q10 ) 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 after dissolving the sugar. It will be possible to add more sugar before adding ice because high temperature is allowing to more sugar in solution.