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Separation of Substances - NCERT - NCERT Questions
Q 1.

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

SOLUTION:

A mixture is separated into different components to remove harmful or unuseful components and to separate the pure components.
(i) Removal of husk from grains of wheat.
(ii) Tea leaves are separated from tea after preparing it.

Q 2.

What is winnowing? Where is it used?

SOLUTION:

Winnowing is used to separate heavier components from the lighter components by blowing air. It is used to separate lighter husk from heavier grains of wheat and rice.

Q 3.

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

SOLUTION:

Husk or dirt particles can be separated from pulses by winnowing. Husk or dirt particles being lighter can be separated from pulses which are heavier.

Q 4.

What is sieving? Where can it be used?

SOLUTION:

Sieving is a process in which small particles are separated from bigger particles by using a sieve. It is used for removing husk from wheat flour. It is also used for separating pebbles and stones from sand.

Q 5.

How will you separate sand and water from their mixture?

SOLUTION:

Sand and water can be separated by sedimentation and then removing the water by decantation.

Q 6.

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

SOLUTION:

Sugar can be separated from wheat flour by sieving. Flour will pass through the sieve while sugar will be retained on the sieve due to bigger size.

Q 7.

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

SOLUTION:

Mud can be separated from water by filtration. Fold a filter paper and keep it in a funnel and pour the muddy water on it. Mud remains on the filter paper while clear water comes through the filter paper and gets collected in the beaker.

Q 8.

Fill in the blanks.
(A) The method of separating seeds of paddy from its stalks is called ............... .
(B) When milk, cooled after boiling is poured into 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 sea water 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 .................. .

SOLUTION:

(a) Threshing, (b) Filtration, (c) Evaporation, (d) Sedimentation and decantation

Q 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 by the process of decantation.

SOLUTION:

(a) False
Since milk and water are miscible, the mixture cannot be separated by filtration.
(b) False
Since salt and powdered sugar are of same size and weight they cannot be separated by winnowing.
(c) False
Since sugar is soluble in tea, it cannot be separated by filtration.
(d) False
Grain and husk can be separated by winnowing, not by decantation.

Q 10.

Lemonade is prepared by mixing lemon juice and sugar in water. Your wish to add ice to cool it. Should you add ice to the lemonade before or after dissolving sugar?

SOLUTION:

We should add ice after dissolving the sugar. Solubility of sugar increases with increase in temperature. Hence, more sugar can be dissolved in water before adding ice.