SEPERATION OF SUBSTANCES
Question: 1. Why do we need to separate different components of a
mixture? Give two examples.
Answer- A mixture may contain one or more unwanted substances
which may be harmful.
These impurities are harmful for our health so, we need to
separate different components of a mixture. Examples: Pebbles are separated
from rice and pulse. Petrol, diesel, kerosene, etc. are obtained from crude oil
by a method called distillation.
Question: 2. What is winnowing? Where is it used?
Answer-The process of separation of grains from husk and hay
with the help of wind is called winnowing. Farmers use this method for
separating the grains from husk and hay.
Question: 3. How will you separate husk or dirt particles from a
given sample of pulses before cooking?
Answer: For this, winnowing can be used.
Question: 4. What is sieving? Where is it used?
Answer-The process of separating solid constituents of different
particle sizes; through a sieve is called sieving. Sieving is used while
separating bran from flour. It is also used while separating pebbles from sand.
Question: 5. How will you separate sand and water from their
mixture?
Answer- The mixture of sand and water can be separated by
sedimentation and decantation.
Question: 6. Is it possible to separate sugar mixed with wheat
flour? If yes, how will do it?
Answer: Yes, it is possible to separate sugar mixed with wheat
flour. It can be done by the process of sieving.
Question: 7. How would you obtain clear water from a sample of
muddy water?
Answer- We can get clear water from a sample of muddy water by
the process of sedimentation, decantation and filtration. Coarser particles of
soil would settle down at the bottom and partially clean water can be separated
by decantation. The water thus obtained can be further clarified by filtration.
Question: 8. Fill in the blanks.
(a) The method of separating seeds of paddy from its stalks is
called---------.
Answer- 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 -------
Answer- filtration
(c) Salt is obtained from sea water by the process of -------
Answer- 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 separations used in this example is
called------------
Answer- sedimentation and decantation
Question: 9 - True or false?
(a) A mixture of milk and water can be separated by filtration.
(F)
(b) A mixture of powdered salt and sugar can be separated by the
process of winnowing. (F)
(c) Separation of sugar from tea can be done with filtration. (F)
(d) Grain and husk can be separated with the process of
decantation. (F)
Question: 10 - Lemonade is prepared by mixing lemon juice and
sugar in water. You wish to add ice to cool it. Should you add to the lemonade
before or after dissolving sugar? In which case would it be possible to
dissolve more sugar?
Answer: Ice should be added after dissolving the sugar.
Saturation level increases with increase in temperature and vice-versa is also
true. So, it is possible to dissolve more sugar in water at room temperature
rather than at lesser temperature.
Additional Questions Based on Separation of Substances
Multiple Choice Questions
Question: 1. The process of settling down of particles of
insoluble solid in a liquid is called
(a) Decantation
(b) sieving
(c) sedimentation
(d) winnowing
Answer- (c) sedimentation.
Question: 2. A solid substance is dissolved in water. Which of the
following methods should be used for separating it?
(a) distillation
(b) evaporation
(c) decantation
(d) filtration
Answer- (b) evaporation
Question: 3. Which of the following properties of particles is
ideal for winnowing?
(a) Difference in size
(b) difference in colour
(c) difference in weight
(d) difference in shape.
Answer: (c) difference in weight
Question: 4. Which of the following methods is used in separation
of chaff from wheat?
(a) handpicking
(b) sieving
(c) Winnowing
(d) sublimation
Answer: (c) Winnowing
Question: 5. Which of the following methods is used in separation
of pebbles from rice?
(a) sieving
(b) Winnowing
(c) sublimation
(d) Handpicking
Answer- (d) Handpicking
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