NCERT Solutions for Class 6 Science Chapter 5 provides knowledge on topics related to Separation of Substances. The detailed answers in this NCERT solution resource will help you to fully understand the concept. By studying this chapter, you will be able to get good grades on the 6th grade exam.
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 unuseful 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 wall 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 mill or at construction sites. In 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 wall 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?
Solution:
Yes it is possible to separate sugar mixed with wheat flour by the following method
a) Mix sugar and wheat flour in water
b) Stir the solution to allow sugar to dissolve
c) Now filter the mixture
d) Filtrate contains sugar solution and residue will be wheat flour.
7. How would you obtain clear water from a sample of muddy water?
Solution:
The following process should be carried out to obtain clear water from muddy water
i) Allow muddy water to stand
ii) Mud gets settled down in the water
ii) Slowly pour water to another container
1. What is strainer?
Ans. Strainer is a kind of sieve which is used to separate a liquid from solid.
2. Name the method used to separate cream from curd.
Ans. Centrifugation.
3. 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.
4. 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 farmer to separate gram, wheat, rice, mustard seeds in his field.
5. Write three methods of separation.
Ans. Handpicking, threshing and winnowing.
6. 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.
7. 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.
8. Define winnowing.
Ans. The process is used to separate components from a mixture in which one component is heavier or lighter than other is called winnowing. Winnowing is done with the help of wind or by blowing air.
9. What do you mean by sieving? Give an example.
Ans. Sieving allows the fine flour particles to pass through the holes of the sieve while the bigger particles or impurities remain on the sieve. For example, in a flour mill, impurities like husk and stones are removed from wheat before grinding it.
10. Match the column:
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 other container.
4. Where is decantation used? Give two examples.
Ans.
(i) Decantation is used to separate insoluble solids or liquid from liquid. Rain water is a mixture of mud and water. It is purified by decantation.
(ii) Oil and water also get separated by this method because oil floats up.
5. How will you prepare cheese (paneer)?
Ans. For making paneer, a few drops of lemon juice sire added to milk as it boils. This gives a mixture of particles of solid paneer and liquid. The paneer is then separated by filtering the mixture through a fine cloth or strainer.
6. Explain the method that can be used for separating the following mixture:
(i) Sand and husk
(ii) Wheat, sugar and stalk
(iii) Water and petrol
(iv) Rice and salt
(v) Sand and salt
Ans.
(i) Mixture of sand and husk: Sand and husk can be separated by the method of winnowing.
(ii) Mixture of wheat, sugar and stalk: For separating stalk from the mixture we should follow the winnowing method because milk is lighter than other two components and get separated. Wheat and sugar can be separated by sieving because they are in different sizes.
(iii) Mixture of water and petrol: Water does not dissolve in petrol. So, it can be separated by the use of separating funnel.
(iv) Mixture of rice and salt: Rice and salt can be separated by sieving.
(v) Mixture of sand and salt: Sand and salt is mixed with water, salt dissolves in water and sand can be separated solution by sedimentation and decantation followed by filtration. After that using evaporation common salt is separated.
Formation of curd is an irreversible as well as a chemical change.’ Justify this statement.
Answer: Formation of curd is an irreversible change because we cannot change curd back into milk. Also, it is a chemical change because new substance that is curd is formed with different property.
3. Water cycle is a natural change. Classify it as a (i) physical or chemical change (ii) a reversible or irreversible change. Also, justify your answer.
Answer:
(1) Water cycle is a natural change and it is also, a physical change because no any new substance is formed, only appearance and physical state is change.
(2) Water cycle is a natural change and it is also a reversible change because in this change water change into vapour state and again change from vapour into liquid state.
4. How can we say that burning of candle is a chemical change but the glowing of bulb is a physical change?
Answer:
We can say that burning of candle is a chemical change because when a candle is burning it gives us light, heat, and smoke which is a new property. On the other hand, glowing of bulb is a physical change because no new substance is formed, only appearance of bulb is change. So, we can say that it is a physical change.
Some examples of reversible changes are:
freezing of water
evaporation
stretching of rubber string
switching ‘on’ or ‘off’ of a light bulb
Some examples of irreversible changes are:
changing of dough into chappatis
making a dress from a single piece of cloth
getting older
making curd from milk
There are about four questions in Chapter 5 of Grade 6 NCERT Science Answers. Students who cannot answer the textbook questions are advised to Download Free PDF From Stromlap.in The solution is created according to the latest CBSE syllabus and guidelines so that students can pass the exam without fear. Daily use of the solution allows students to answer complex questions that arise during the exam. Professional faculty design solutions aimed at helping students succeed in their annual exams
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