NCERT Solutions for Class 6 Science Chapter 3 Separation of Substances

NCERT
SOLUTIONS
CLASS - 6TH

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Class : 6th
Subject : Science
Chapter : 5
Chapter Name : SEPARATION OF SUBSTANCES

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

Answer. Different components of a mixture are separated in unrequired components
from a mixture or sometimes, useful components from a mixture. order to either
separate the to separate more than one

For example, grain purchased from shops can contain several impurities such as pieces of
stone, husk, broken grains, etc. Thus, grain is separated from these impurities to make it
edible. Similarly, after preparing tea, we strain it to remove the used tea leaves from tea.

Q2 What is winnowing? Where is it used?

Answer. Winnowing is the process of separation of the heavier components from the
lighter components of a mixture by wind or by blowing air. It is generally used by farmers
to separate the lighter impurities such as husk particles from the heavier grains.

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

Answer. The dirt particles that are present in the pulses are removed by washing the
latter with water. Being heavier, the pulses settle down, while the dirt particles being
lighter keep �oating in water. This process is called sedimentation. The dirty water can
be removed by the method of decantation, leaving the pulses at the bottom.

Q4 What is sieving? Where is it used?

Answer: Sieving is the method of separation of �ne particles from bigger particles by

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allowing the �ner particles to pass through the holes of a sieve, leaving the bigger
particles in the sieve itself. It is generally used in homes to separate �our from impurities
such as pieces of stone, stalk, and husk. It is also used at construction sites to separate
sand from small stones.

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

Answer. Sand is not soluble in water. Hence, the mixture of sand and water can be
separated by two methods:
1. Combination of sedimentation and decantation: As sand is insoluble and heavier than
water, it settles down at the bottom of the container containing the mixture. This
process is called sedimentation. After the process of sedimentation is complete, water is
slowly transferred to another container and sand remains in the original container. This
process is called decantation.
2. Filtration: the mixture is poured on a strainer or a piece of cloth or a �lter paper so
that the water goes through the strainer and the sand remains on the strainer.

Q6 Is it possible to separate sugar mixed with wheat �our? If yes, how will you do it?

Answer: Yes. It is possible to separate a mixture of sugar and wheat �our. This can be
done by the process of sieving. If the mixture of sugar and wheat �our is allowed to pass
through a sieve, then the �ne wheat �our particles would pass through the sieve, the
sugar particles would be retained by the sieve.

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

Answer: Clear water can be obtained from a sample of muddy water by the method of
�ltration. In this method, the sample of muddy water is poured through a cloth having
�ne pores or through a �lter paper. Water will pass through the �ltering medium, leaving
behind the mud.

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Q8 Fill in the blanks:
(a) The method of separating seeds of paddy from its stalk is called _____
(b) When milk is cooled after boiling and poured on a piece of cloth, 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.
Clear water was then poured from top. The process of separation used in this example is
called _______.

Answer. (a) The method of separating seeds of paddy from its stalk is called threshing.
(b) When milk is cooled after boiling and poured on a piece of cloth, cream (malai) is left
behind on it. This process of separating cream from milk is an example of �ltration.
(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.
Clear water was then poured from 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 �ltration.
(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 �ltration.
(d) Grain and husk can be separated with the process of decantation.

Answer. (a) False
(b) False
(c) False
(d) False

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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 sugar. When the temperature is high then
more sugar can be dissolved. After mixing ice it gets cool and less sugar will dissolve in

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Book : Science NCERT Solutions | Chapter - 5 Science

it.

Page : 45 , Block Name : Exercise

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