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Std 6, Sub: Basic Science, Chapter 5, Separation of Substances, ( textbook exercise ), 1. Why do we need to separate different components of a mixture? Give two, examples., Ans: Among different components of mixture there are many substances, which are harmful or not useful for us. To remove these harmful or useful, components we need to separate them. For example:, (a) Tea leaves are separated from the liquid with a strainer while preparing, tea., (b) Stone pieces from wheat, rice or pulses are picked out by hand., 2. What is winnowing? Where is it used?, Ans: Winnowing is used to separate heavier and lighter components of a, mixture by wind or by blowing air. This process is used by farmers to separate, lighter husk particles from heavier seeds of grain., 3. How will you separate husk or dirt particles from a given sample of pulses, before cooking?, Ans: Husk or dirt particles can be separated by winnowing, being lighter they, will fly away from pulses., 4. What is Sieving? Where can it be used?, Ans. Sieving is a process by which fine particles are separated from bigger, particles by using a sieve. It is used in flour mills or at construction sites. In a, flour mill, impurities like husks and stones are removed from wheat. Pebbles, and stones are removed from sand by sieving., 5. How will you separate sand and water from their mixture?, Ans. We will separate sand and water by sedimentation and decantation, method. First we leave this mixture for some time. After some time, the sand, which is; heavier is settled down at the bottom. After that we will pour water, into another container and the mixture will be separated., 6. Is it possible to separate sugar mixed with wheat flour? If yes, how will you, do it?, Ans. Sugar can be separated from wheat flour by sieving. Due to the, difference in the size of particles, sugar will stay on the sieve and wheat flour, will pass through it.
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7. How would you obtain clear water from a sample of muddy water?, Ans. We will obtain clear water from a sample of muddy water by the process, of filtration., A filter paper is one such filter that has very fine pores in it. . A filter paper, folded in the form of a cone is fixed in a funnel. The mixture is then poured on, the filter paper. Solid particles in the mixture do not pass through it and remain, on the filter., Fill in the blanks:, (a) The method of separating seeds of paddy from its stalks is called, 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, filtration, (c) Salt is obtained from sea water by the process of 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, sedimentation and decantation, True or false, (a) A mixture of milk and water can be separated by filtration. -- False, (b) A mixture of powdered salt and sugar can be separated by the process of, winnowing. -- false, (c) Separation of sugar from tea can be done with filtration. -- false, (d) Grain and husk can be separated with the process of decantation. -- false, 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 ?, Ans. 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 it., Extra questions, 1. What is a strainer?, Ans. Strainer is a kind of sieve which is used to separate a liquid from solid., 2. How will you separate mango from a mixture of mango and apple?, Ans. By picking.
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3. You are given a mixture of salt and sand. Can you separate them by, picking?, Ans. No, we cannot separate them by picking., 4. Name the method used to separate the pieces of stone from grain., Ans. Handpicking., 5.How can you separate grains from stalks?, Ans. We separate grains from stalks by threshing., 6.Name the process used to separate heavier and lighter components of a, mixture., Ans. Winnowing., 7.What is evaporation?, Ans. The process of conversion of water into vapour is called evaporation., 8. Name the method by which we get salt from ocean water., Ans. Evaporation., 9.Define condensation., Ans. The process of conversion of water vapour into liquid form is called, condensation., 10. Write the opposite process of evaporation., Ans. Condensation., l1.What is the mixture?, Ans. When two or more than two substances are mixed together in any ratio, then it is called a mixture., 12. Write various methods of separation of components from their mixture., Ans., Handpicking, Threshing, Winnowing, Sedimentation, Decantation, Filtration, Evaporation, Condensation, 13. Define the term handpicking., Ans. The process used to separate slightly larger particles from a mixture by, hand is called handpicking. For example: Stone pieces can be separated from, wheat or rice by handpicking., 14. What do you mean by threshing? Where is it used?, Ans. Threshing is a process in which we separate grain from stalks. This, process is used by farmers to separate gram, wheat, rice, and mustard seeds, in his field.
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15. Write three methods of separation., Ans. Handpicking, threshing and winnowing., 16. How will you separate oil and water from their mixture?, Ans. Oil, being lighter than water, will float on it. Two distinct layers are formed, and slowly oil is allowed to flow into another container and is separated from, water. Separating funnel can also be used to separate the two., 17. What is evaporation?, Ans. The process of conversion of water into vapour is called evaporation., This process takes place continuously where water is present. Common salt, from sea water is obtained using this method., LONG ANSWER TYPE QUESTIONS, 1. What is threshing?, Ans. Threshing is a process that is used to separate grain from stalks. In this, process the stalks are beaten to free the grain seeds. Sometimes threshing is, done with the help of bullocks. Machines are also used to thresh large, quantities of grain., 2. Describe the method to obtain salt from sea water., Ans. Sea water contains many salts mixed in it. One of them is common salt,, when sea water is allowed to stand in shallow pits, water gets evaporated by, sunlight and slowly turns into water vapour. In a few days, the water, evaporates completely leaving behind the solid salts. Common salt is then, obtained from this mixture of salts by further purification., 3. What is decantation?, Ans. Decantation is a process of separation of insoluble solids from liquid. The, suspension of solid particles in liquid is allowed to stand for some time. The, solid particles then settle down at the bottom of the container and clean water, goes up. Without disturbing the settled particles the clean water is transferred, into another container.
