Separation of Substances: science class six
NCERT SOLUTION
Question (1) Why do we need to separate different components of a mixture? Give two examples.
Answer:
We need to separate different components of a mixture to get rid of unwanted materials present in it.
Example In grains like rice, wheat, pulses, etc. may have many stones and other unwanted things present. These unwanted materials are needed to be separated out from the mixture to make the substance useful.
In water there are many impurities like mud, sand, and bacteria are present. These impurities are separated out to make water more useful.
Question (2) What is winnowing? Where is it used?
Answer:
Winnowing is the process in which lighter husks are separated from heavier grains like wheat. In this method, the mixture is allowed to fall from a height. In this process, husks are lighter and blown out slightly far from grains.
Winnowing is used to separate out husk from grains.
Question (3) How will you separate husk or dirt particles from a given sample of pulses before cooking?
Answer:
Husk or other dirt particles are generally separated out using hand picking or a method of sieving from pulse before cooking.
Question (4) What is sieving? Where is it used?
Answer
Sieving is the process to separate out comparatively thick particles from grains. Sieving is used to separate the components that are of different sizes.
In this method, a sieve having holes of the proper size is used. The bigger particles are retained by the sieve where as the smaller ones pass through it.
This method is used for separating the chaff from wheat flour, separating fine sand from gravel, etc.
Question (5) How will you separate sand and water from their mixture?
Answer
Sand and water are separated out from the mixture generally using the method of sedimentation.
In the process of sedimentation mixture of sand and water is allowed to settle down. Sand which is heavier is settled down in the bottom. After that water is poured out.
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 by using the method of sieving.
Question (7) How would you obtain clear water from a sample of muddy water?
Answer To separate out clear water from the sample of muddy water, the process of decantation or process of filtration is used.
Question (8) Fill in the blanks
(a) The method of separating seeds of paddy from its stalk 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: Churning
(c) Salt is obtained from seawater 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 separation 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.
Answer: False
Correct Statement The mixture of milk and water can be separated out using the method of evaporation.
(b) A mixture of powdered salt and sugar can be separated by the process of winnowing.
Answer: True
Explanation A mixture of powdered salt and sugar can be separated out using the process of winnowing, but this method is not used to separate this type of mixture.
The better method is sieving to separate the mixture of sugar and powdered salt. Sugar which is in the form of granules is left in the sieve while powdered salt will be fallen from the pores of the sieve.
(c) Separation of sugar from tea can be done with filtration.
Answer: False
Correct statement The mixture of sugar and tea can be separated out using the method of evaporation.
(d) Grain and husk can be separated with the process of decantation.
Answer: True
Explanation: Grain and husk can be separated with the process of decantation, but a better process is winnowing to separate the husk from grains.
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.
Because anything can be dissolved more easily in a solution having less temperature. Since after adding the ice the temperature of the lemonade will go down, so it will become slightly difficult to dissolve the sugar in it.
Although, we can add sugar either before adding the ice or after adding the ice. Both conditions will be suitable in the case of making lemonade.
Extra Questions
Short Answer type questions
Question (1) What is decantation?
Answer: The process of pouring out clear liquid without disturbing the sediments is called decantation.
Question (2) What is evaporation?
Answer: The process in which the liquid part of a mixture gets converted into vapour leaving the solid component of the mixture behind is called evaporation.
Question (3) What is filtration?
Answer: A process of separating out insoluble solid substance from a liquid using filter is called filtration.
Question (4) What is hand picking?
Answer: Separation of a mixture having solid particles of different shape, size, etc. by picking them with hands is called hand–picking. This method is used when impurities are in less amount.
Question (5) What is heterogeneous mixture?
Answer: Mixtures in which the particles of the substances present can be seen easily are called heterogeneous mixtures. Some heterogeneous mixtures are Water +oil, Chalk + water, Dust in air, etc.
Question (6) What is homogenous mixture?
Answer: Mixtures in which the particles of the substances present cannot be seen or distinguish are called homogeneous mixtures. Some homogeneous mixtures are solution of salt or sugar in water.
Question (7) What is mixture?
Answer: Materials which contain two or more substances in any proportion are called mixture.
Question (8) What is sedimentation?
Answer: The process of settling down of heavy, insoluble solid particles mixed in a liquid is called sedimentation.
Question (9) What is sieving?
Answer: A method, used to separate the different sized components of a mixture, by using sieve is called sieving.
Question (10) What is threshing?
Answer: Separation of grains from harvested crop using a thresher is called threshing.
Question (11) What is winnowing?
Answer: The process of separation of lighter particles from heavier ones by wind is called winnowing. Winnowing is used to separate husk and other lighter impurities from grains.
Question (12) What is Solution?
Answer: The homogeneous mixture of water or any other solvent and a substance dissolve in it is called a solution.
Question (13) What is Saturated solution?
Answer: A solution in which no more solute can be dissolved at a given temperature is called a saturated solution.
Question (14) What do you mean by pure substances?
Answer: A pure substance has only one kind of particles.
Question (15) Which process is used to separate grain and husk?
Answer: Grain and husk can be separated using the process of winnowing.
Fill in the blanks
(1) Women sometimes use the method of _______ to remove unwanted substances from eatables like rice and pulses.
Answer: Hand picking
(2) Common salt is prepared on a large scale through the process of ________.
Answer: Evaporation
(3) Separation of tea leaves from tea juice is done by a process called _________.
Answer: filtration
(4) Muslin cloth is used to ___________.
Answer: filter.
(5) Pond water is a ____________mixture.
Answer: heterogeneous
(6) Peas are separated from a mixture of peas and white gram by _______.
Answer: Hand picking
(7) Cream is separated from milk by ______.
Answer: Churning
(8) A filter paper is used for separating ______ particles from a _____.
Answer: Solid, solution
(9) Crystallization is used to obtain _________ solids from a given solution.
Answer: Pure
(10) _______ is generally used by farmers to separate the grains from the stalks after harvesting.
Answer: Threshing.
Questions based on true and false statement
Write True for true statement and False for false statement
(1) All mixtures are heterogeneous.
Answer: False
Correct Statement Mixture may be heterogeneous or homogeneous.
(2) Common salt obtained from sea water contains many impurities.
Answer: True
(3) The salt from a solution of salt in water can be recovered by evaporation.
Answer: True
(4) Cream can be separated from milk by sieving.
Answer: False
Correct Statement Cream can be separated out from milk by the method of churning.
(5) The process of conversion of water vapour into liquid is called condensation.
Answer: True
(6) For separating chaff from wheat flour the method of filtration is used.
Answer: False
Correct statement Chaff can be separated out from the wheat flour using the method of sieving.
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