NCERT TEXTBOOK EXERCISES
(Pages 44-45)
Question 1.
Why do we need to separate different components of a mixture? Give two examples.
Answer:
We need to separate different substances present in a mixture for the following purposes :
(1) To remove the unuseful or harmful component.
For example – removing tea leaves after making tea.
(2) To obtain the useful component – For getting wheat/rice grains after separating husk, dirt, etc.
(3) To remove impurities for getting a pure sample,
For example – obtaining sugar crystals from jaggery (gur) or salt from seawater.
Question 2.
What is winnowing? Where is it used?
Answer :
Winnowing is the process of separating wheat or rice grains from the husk. Wheat grains and husk are different in weight, husk is lighter than wheat. When the mixture is allowed to fall down from a height, the wind carries the lighter husk with it and the heavy wheat grains fall vertically down on the ground.
Question 3.
How will you separate husk or dirt particles from a given sample of pulses before cooking?
Answer :
Husk or dirt particles are separated from pulses before cooking by hand-picking.
Question 4.
What is sieving? Where is it used?
Answer :
Sieving is the method to separate particles of different sizes. Undesirable particles can be separated from grains by this method. The size of holes in the sieves depends upon the size of the particles. In cashew nut factories, the cashew nuts of different sizes are separated by sieving. Jewellers also separate pearls of different sizes by this method.
Sieving flour before consuming is not a good practice. We should consume it along with the husk because husk provides roughage which is useful for our body in proper bowel movement.
Question 5.
How will you separate sand and water from their mixture?
Answer:
This can be done by taking a beaker or a glass tumbler half-filled with the given sample of water. Water is stirred thoroughly before keeping it undisturbed for some time. The sand being heavy settles down at the bottom of the beaker. Now, the clear water is poured into another beaker without disturbing the layer of sand with the help of a glass rod.
Question 6.
Is it possible to separate sugar mixed with wheat flour? If yes, how will you do it?
Answer :
Yes, we can separate sugar from wheat flour by sieving. In the mixture of sugar and wheat flour, sieving allows the fine flour particles to pass through the holes of the sieve, while the sugar particles remain on the sieve.
Question 7.
How would you obtain clear water from a sample of muddy water?
Answer:
Muddy water is cleared by the process of loading. Take a piece of alum, tied with a thread, it is swirled in water; then after some time, the water becomes clear on standing. The water becomes clear because the mud particles get loaded by the alum particles and become heavy. The loaded mud particles settle down at the bottom of the container. The water, therefore, becomes clear and can be decanted for further use.
Question 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 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) threshing
(b) filtration
(c) evaporation
(d) decantation
Question 9.
True or false:
(a) A mixture of milk arid 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) False
(b) False
(c) False
(d) False
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 sugar. It would be possible to dissolve more sugar before adding ice.
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Extra Questions for Class 6 Science Chapter 5 Separation of Substances with Answers Solutions
Separation of Substances Class 6 Extra Questions Very Short Answer Type
Question 1.
What are the components of air?
Answer:
Oxygen, carbon dioxide, nitrogen, etc.
Question 2.
What are the components of milk?
Answer:
Milk-proteins, calcium, cream and water.
Question 3.
What are the types of mixture?
Answer:
Heterogeneous mixtures and homogeneous mixtures.
Question 4.
Name the process used to separate heavier and lighter components of a mixture.
Answer:
Winnowing
Question 5.
Mention one purpose of separating the constituents of a mixture.
Answer:
To remove the undesirable substances.
Question 6.
When handpicking is used?
Answer:
Handpicking is used to separate undesirable components having different shape, size, colour and are present in small amount.
Question 7.
Which type of separation process is used in cashewnut factories?
Answer:
Sieving
Question 8.
Name the process used to obtain salt from sea water.
Answer:
Evaporation
Question 9.
Write opposite of the process of condensation.
Answer:
Evaporation
Question 10.
What is effect of temperature on solubility?
Answer:
Solubility increases when temperature increases.
Question 11.
Name the process of obtaining clear water from muddy water in which alum is used.
Answer:
Loading
Question 12.
Which method is used to separate a mixture of tea leaves and iron filings?
Answer:
By magnet
Question 13.
Which gas dissolved in water helps aquatic animals to breathe?
Answer:
Oxygen gas
Question 14.
Name the method by which you can separate butter from milk.
Answer:
Centrifugation
Question 15.
Which liquid is called as universal solvent?
Answer:
Water
Question 16.
Name some materials that are used as filters.
Answer:
Cotton, ceramic, fine cloth, filter paper, etc.
Question 17.
Give one example of sieving used in everyday life.
Answer:
Separation of bran from flour.
Question 18.
Which substance is used for loading?
Answer
Alum
Question 19.
Which process is used to separate bacteria from water?
Answer:
Filtration by using bacteria proof filters.
Question 20.
Name the process of separating two immiscible liquids.
Answer:
Decantation
Separation of Substances Class 6 Extra Questions Short Answer Type
Question 1.
Why mixtures need to be separated?
Answer:
The main reason for separating the mixtures are:
To remove undesirable substances.
To get desirable substances.
To obtain highly pure substances.
Question 2.
What is handpicking? When this method is used?
Answer:
The method in which the constituents are separated by simply picking them up by hand is called hand-picking. It is used when there is a difference in size, colour, shape of desirable and undesirable constituents.
Question 3.
What is evaporation? What is the significance of this process?
Answer:
The changing of liquid into vapours is called evaporation. The process of evaporation is used on a large scale to obtain common salt from sea water.
Question 4.
What is threshing?
Answer:
The process of separating grains from the stalks is called threshing.
Question 5.
What is the use of decantation?
Answer:
Decantation is used to separate insoluble solids from liquids. Two immiscible liquids are also separated by this process.
Question 6.
What is a mixture?
Answer:
When two or more than two substances are mixed together in any ratio then it is called a mixture.
Question 7.
What is decantation?
Answer:
Decantation is the process of separating insoluble solids from liquids. A suspension of solid particles in liquid is allowed to stand for some time. Solid particles settle down at the bottom. The clear water is then transferred into another beaker.
Question 8.
State one use of the method of winnowing.
Answer:
The method of winnowing is used to separate husk from various types of grain like wheat, rice, etc. Give one use of the handpicking method of separating mixtures in daily life. The method of handpicking is usually used to separate undesirable substances such as small pieces of stones from wheat, rice and pulses.
Question 9.
Define the term sedimentation.
Answer:
The process in which heavier, insoluble solid settles down in a solution is called sedimentation.
Separation of Substances Class 6 Extra Questions Long Answer Type
Question 1.
Elaborate the process of filtration.
Answer:
Filtration is the process of separating an insoluble solid from a liquid with the help of a filtering agent like filter paper, cloth, strainer, etc. During filtration, the solid insoluble substance is retained at the filter paper as residue while the liquid free from any suspended matter passes through the filter paper and is collected as filtrate.
There are certain soluble components infiltrate which can be separated by the process of evaporation followed by crystallization.
Question 2.
What is meant by saturated and unsaturated solution?
Answer:
Saturated solution: At any particular temperature, a solution that has dissolved as much solute as it is capable of dissolving, is said to be a saturated solution.
Unsaturated solution: A solution in which more quantity of solute can be dissolved without raising the temperature of the solution is called unsaturated solution.
Question 3.
What is the effect of temperature on a saturated solution?
Answer:
(i) When a saturated solution is heated to a higher temperature, then it becomes unsaturated because the solubility of solute increases with increase in temperature of the solution.
(ii) When a saturated solution is cooled to a lower temperature, then some of the dissolved solute separates out in the form of solid crystal because the solubility of solute decreases on cooling the solution.
Question 4.
What is the importance of centrifugation? How it is done?
Answer:
Centrifugation is the process of separating suspended particles from a liquid by rotating the liquid at a high speed.
The mixture is taken in a closed bottle and rotated at a high speed. The heavy particles settle at the bottom while light particles remains behind. The method is also used to separate cream from milk. Cream being lighter than milk, floats at the top of the mixture.
Question 5.
What is loading? How will you obtain clear water from muddy river water by the process of loading?
Answer:
The suspended small particles of muddy water are negatively charge which inhibit them to settle down due to repulsion. On adding alum to this muddy water, removes the negative charge from the particles. This particles forms clump easily, become heavier and settles down.
This process is called loading. Loading helps in purification of water from small suspended particles which do not settles down easily and quickly. The clear water after settling down of suspended particles is decanted in another container and is comparatively clearer.
Separation of Substances Class 6 Extra Questions HOTS
Question 1.
Rahul by mistake mixed sugar with salt. What method he must adopt to quickly separate this mixture?
Answer:
He must use the method of sieving for separating salt and sugar.
Question 2.
Can we separate the mixture of sugar and milk?
Answer:
No
Question 3.
Which method of separation will you adopt to separate a mixture of wheat flour, moong dal and chana?
Answer:
We will adopt the method of sieving followed by handpicking to separate the mixture. Sieving will separate wheat flour from moong dal and chana. Handpicking will separate moong dal from chana. Sieve with appropriate pores can also be used to separate moong dal from chana.
Question 4.
Suggest any two methods to separate suspended particles of mud from water.
Answer:
Loading with alum and centrifugation.
Question 5.
Is there any method through which we can separate different components of ink?
Answer:
Chromatography technique.
Separation of Substances Class 6 Extra Questions Value Based Question (VBQs)
Question 1.
Some shopkeepers mix many cheap and harmful substances in the food materials. This process is called adulteration. Anybody who are involved in such kind of illegal practices are liable for imprisonment.
(a) Why shopkeepers mix cheap and harmful substances in food materials?
(b) How will you separate impurities from grains and pulses?
(c) What values of shopkeepers are shown here?
Answer:
(a) Shopkeepers add these undesirable substances to increase the quantity of the food materials and thus their profit.
(b) Through handpicking.
(c) Shopkeepers observing such practices are greedy, self-centred, criminal-minded and soulless.
Question 2.
There were guests at Sonam’s house. Sonam thought of making lemonade for them. She dissolved sugar in chilled water and observe that sugar was taking long time to dissolve. Meanwhile, Sonam’s mother came and asked her to transfer the upper chilled water in another container and then add water at normal temperature to this sugar settled at bottom.
Sonam then found it easy to dissolve the sugar for lemonade.
(a) What is saturated solution?
(b) What is the effect of temperature on the capacity of water in dissolving substances?
(c) What will happen if we cool a supersaturated solution?
(d) What value of Sonam is shown here?
Answer:
(a) A saturated solution is the solution which cannot dissolve any more solute in it at a given temperature.
(b) With increase in temperature solubility of a substance increases in water and vice versa.
(c) When a supersaturated solution is cooled, it form crystals of the salt. This process is known as crystallization.
(d) Sonam is a good host, learner, helpful girl.