Category: Science

NCERT Solutions for Class 6 Science Chapter 4 Sorting Materials Into Groups

Topics and Sub Topics in Class 6 Science Chapter 4 Sorting Materials Into Groups:

Section Name	Topic Name
4	Sorting materials into groups
4.1	Objects around us
4.2	Properties of materials

Q. 1. Name five objects which can be made from wood.
Ans.
(i) Table
(ii) Chair
(iii) Doors
(iv) Boat
(v) Bed

Q.2. Select those objects from the following which shine:
Glass bowl, plastic toy, steel spoon, cotton shirt
Ans. Glass bowl and steel spoon are shining objects.

Q.3. Match the objects given below with the materials from which they could be made. Remember, an object could be made from more than one material and a given material could be used for making many objects.

Q. 4. State whether the statements given below are ‘true’ or ‘false’.
(i) Stone is transparent, while glass is opaque.
(ii) A notebook has lustre while eraser does not
(iii) Chalk dissolves in water.
(iv) A piece of wood floats on water.
(v) Sugar does not dissolve in water.
(vi) Oil mixes with water. 
(vii) Sand settles down in water.
(viii) Vinegar dissolves in water.
Ans.
(i) False
(ii) False
(iii) False
(iv) True
(v) False
(vi) False
(vii) True
(viii) True

Q. 5. Given below are the names of some objects and materials:
 Water, basket ball, orange, sugar, globe, apple and earthen pitcher Group them as:
(a) Round shaped and other shapes
(b) Eatables and non-eatables
Ans.
(a) (i) Round shaped: Basket ball, apple, orange, globe, earthen pitcher.
(ii) Other shapes: Water, sugar.
(b) (i) Eatables: Water, orange, sugar and apple.
(ii) Non-eatables: Basket ball, globe and earthen pitcher.

Q. 6. List all the items known to you that float on water. Check and see if they will float on an oil or kerosene.
Ans. (A) List of some items that float on water:

1. Paper
2. Wood
3. Thin plastic sheets
4. Wax
5. Ice
6. Thermocol
7. Oil

(B) List of items that float on an oil:

1. Paper
2. Plastic sheet
3. Wax
4. Thermocol
5. Wood

(C) List of items that float on kerosene:

1. Paper
2. Thermocol
3. Thin plastic sheet

Q. 7. Find the odd one out from the following:
(a) Chair, Bed, Table, Baby, Cupboard
(b) Rose, Jasmine, Boat, Marigold, Lotus
(c) Aluminium, Iron, Copper, Silver, Sand
(d) Sugar, Salt, Sand, Copper sulphate
Ans.
(a) Baby (all others are non-living)
(b) Boat (all others are flowers)
(c) Sand (all others are metals)
(d) Sand (all others are soluble in water)

EXTRA QUESTIONS for Class 6 Science Chapter 4 

Class 6 Science Chapter 4 VERY SHORT ANSWER TYPE QUESTIONS

1. Why do we need to group materials? Give one reason.
Ans: We often group materials for our convenience. It helps to describe their properties.

2. Suggest two bases on which we can group objects.
Ans:
(i) Material used in making the object, e.g. wood or metal/plastic.
(ii) Material of the object is soft or hard, or substance is soluble or insoluble in water.

3. Is a substance which can be compressed soft or hard?
Ans: Soft.

4. Select a lustrous material out of the following substances:
Ans: Aluminium.

5. Which material is generally used for making pens?Wood, aluminium, plastic, cotton 
Ans:Plastic or metal.

6. Is oil soluble in water?
Ans: Oil does not dissolve in water so it is insoluble in water but floats on the surface of water.

7. Name two objects which are made from opaque materials.
Ans: Wooden doors, blackboard/steel plate.

8. What is common between salt and sand?
Ans: Both have mass and are in solid state.

9. List three liquids which are transparent.
Ans. Water, alcohol and Acetone/Benzene.

10. Write two substances which are made from leather.
Ans: Belt and shoes.

11. Name some substances which are made from plastics.
Ans: Toys, plates, cups, buckets, baskets.

12. Which is more hard, sponge or iron?
Ans: Iron is harder than sponge.

13. Write two gases which are soluble in water.
Ans: Oxygen, Carbon dioxide.

14. Name two gases which are insoluble in water.
Ans: Hydrogen and Nitrogen.

Class 6 Science Chapter 4 SHORT ANSWER TYPE QUESTIONS

1. Write any four properties of materials.
Ans:
(a) Appearance
(b) Hardness
(c) Solubility
(d) Float or sink in water
(e) Transparency

2. Why is a tumbler not made with a piece of cloth?
Ans: We use tumblers made of glass, plastic and metal to keep a liquid. These substances can hold a liquid.
A tumbler made of cloth cannot hold a liquid because:
(i) Cloth piece is not hard enough to hold liquids and
(ii) Cloth piece has very minute pores through which the’liquid oozes out.

3. What are the similarities between iron, copper and aluminium?
Ans:
(a) They all have lustre,
(b) They are all metals,
(c) They are hard.

4. Mention some materials which are made up of paper.
Ans: Books, notebooks, newspapers, toys, calendars, etc.

5. Why is water important for our body?
Ans: Water can dissolve a large number of substances, so it is needed by the body. It is also major part of our body cells.

6. What is the basis for sorting materials?
Ans: Materials are grouped on the basis of similarities or dissimilarities in their properties.

7. What is the reason for grouping materials?
Ans: Materials are grouped for our convenience to study their properties and also observe any patterns in these properties.

9. Make a table of different types of objects that are made from the same material.

10. Make a table and find out whether the following materials mix with water: Vinegar, Lemon juice, Mustard oil, Coconut oil, Kerosene.

 11. Metals have lustre (shine). Give reason why some metal articles become dull and loose their shine.
Ans: Metals when exposed to air react with moisture and gases present in it, thereby forming a dull layer of some other compound on it.

12. Kerosene, coconut oil, mustard oil do not dissolve in water, even on shaking. They separate after sometime forming two different layer. Explain why.
Ans: The molecules of water do not intermingle (mix) with the molecules of oil. The space between the molecules of water is not taken by oil, so they are immiscible in water.

13. Name a non-metal that has lustre.
Ans: Iodine.

14. Metals generally occur in solid state and are hard. Name a metal that exists in liquid state and a metal that is soft and can be cut with knife.
Ans: Mercury is a metal that exists in liquid state. Sodium and Potassium are soft metals and can be cut with knife.

15. Name the naturally occuring hardest substance known.
Ans: Diamond, it is made up of carbon (non-metal).

16. Why is water called a universal solvent?
Ans: Water dissolves a large number of substances in it. So it is called universal solvent.

Class 6 Science Chapter 4 LONG ANSWER TYPE QUESTIONS

1. ‘Grouping of objects helps the shopkeeper.’ Justify the statement.
Ans: Proper grouping of objects helps shopkeeper in the following ways:
(i) He can locate the required object easily and quickly.
(ii) He can easily come to know what stocks are going to finish and he should purchase them for his customers.

2. Describe an experiment to prove that water is transparent.
Ans: Take a beaker half-filled with clean water. Put a coin in beaker of water.
Place the beaker undisturbed for a few minutes where enough light is present. Now, observe the coin immersed in water from the top of the beaker. Are you able to see the coin? You can clearly see the coin immersed in water. This proves that water is a transparent liquid.

3. Write an experiment to show that our palm is translucent.
Ans: Cover the glass of a torch with your palm at a dark place. Switch on the torch and observe from the other side of palm. We see that the light of torch passes through palm but not clearly. This experiment shows that our palm becomes translucent when a strong beam of light passes through it.

4. How can you show that some solids like sugar, salt are soluble in water whereas solids like chalk powder and sand are not soluble in water?
Ans: Collect samples of sugar, salt, chalk powder and sand. Take four beakers. Fill each one of them about two-third with water. Add a teaspoonful of sugar to the first beaker, salt to the second, chalk powder to the third and sand to the fourth. Stir the contents of each beaker with a spoon/stirrer.

Wait for a few minutes and observe what happens to the substances added to the’ water.
Note down your observations in the following table.

Inference:
(i) Sugar and salt are soluble in water.
(ii) Chalk powder and sand are insoluble in water.

NCERT Solutions

NCERT Solutions for Class 6 Science Chapter 2 Components of Food

The topics and Sub Topics in Class 6 Science Chapter 2 Components of Food:

Section Name	Topic Name
2	Components of Food
2.1	What do Different Food Items Contain?
2.2	What do Various Nutrients do For Our Body?
2.3	Balanced Diet
2.4	Deficiency Diseases

Class 6 Science Chapter 2 Textbook Questions Solved

1. Name the major nutrients in our food.
Ans: The major nutrients in our food are carbohydrates, proteins, fats, vitamins and minerals.
The table below shows the nutrients present in some food items:

2. Name the following: 
(a) The nutrients which mainly give energy to our body.
(b) The nutrients that are needed for the growth and maintenance of our body.
(c) A vitamin required for maintaining good eyesight.
(d) A mineral that is required for keeping our bones healthy.
Ans:
(a) Carbohydrates
(b) Proteins
(c) Vitamin A
(d) Calcium

3. Name two foods each rich in:
(a) Fats
(b) Starch
(c) Dietary fibre
(d) Protein
Ans:
(a) Ghee, butter,
(b) Raw potato, rice,
(c) Spinach, cabbage, carrot, ladies finger, (any two)
(d) Milk, egg, fish, meat, pulses (any two).

4. Tick (/) the statements that are correct, cross (X) those which dire incorrect.
(a) By eating rice alone, we can fulfill nutritional requirement of our body,
(b) Deficiency diseases can be prevented by eating a balanced diet.
(c) Balanced diet for the body should contain a variety of food items.
(d) Meat alone is sufficient to provide all nutrients to the body.

5. Fill in the blanks:
(a) ________ is caused by deficiency of Vitamin D. ,
(b) Deficiency of_________ causes a disease known as beri-beri.
(c) Deficiency of Vitamin C causes a disease known as________________ .
(d) Night blindness is caused due to deficiency of_______________ in our food.
Ans:
(a) Rickets
(b) Vitamin B1
(c) Scurvy
(d) Vitamin A

EXTRA QUESTIONS for Class 6 Science Chapter 2

Class 6 Science Chapter 2 VERY SHORT  ANSWER TYPE QUESTIONS

1. Do all meals consist of the same food items?  
Ans: No, all meals do not have the same food items.

2. Why should a meal have different food items?
Ans: A meal should have different food items because our body needs different kinds of nutrients for proper functioning.

3. Do all foods contain all the required nutrients?
Ans: No, all foods do not contain sill the nutrients required by our body.

4. Name two main types of carbohydrates found in our food.
Ans:
(i) Starch                                                  (ii) Sugar

5. What are carbohydrates?
Ans: The compounds of carbon, hydrogen and oxygen which provide energy for our body are called carbohydrates.

6. What happens when two or more drops of iodine solution fall on starch substance?
Ans: The colour of the substance becomes blue-black.

7. If any food item gives blue-black colour with iodine then which nutrient is present in the food?
Ans: Starch.

8. Name two substances which provide carbohydrates.
Ans:
(i) Potato
(ii) Rice/wheat/maize/sugar

9. Name the food nutrient indicated by an oily patch on paper.
Ans:An oily patch on paper shows the presence of fat.

10. Name two energy-providing nutrients.
Ans:
(i) Carbohydrates
(ii) Fats

11. Name a nutrient which helps in repairing the damaged body cells.
Ans: Proteins.

12. Name two nutrients which protect the body from diseases.
Ans:
(i) Vitamins
(ii) Minerals

13. Name two plant food items which provide proteins.
Ans:
(i) Dal (pulses)
(ii) Soyabean

14. Name two sources of proteins provided by animals.
Ans:
(i) Milk
(ii) Eggs

15. Which type of food is called body-building food?
Ans: The food containing proteins is called body-building food.

16. Name two food items which provide fats.
Ans:
(i) Oils
(ii) Ghee

 17. Name various types of vitamins.
Ans: Various types of vitamins are:

1. Vitamin A,
2. Vitamin B-complex,
3. Vitamin C,
4. Vitamin D,
5. Vitamin E,
6. Vitamin K.

 18. Name a vitamin which represents a group of vitamins.
Ans: Vitamin B-complex.

 19. Name two sources of Vitamin A.
Ans:
(i) Fish-oil
(ii) Milk

 20. Write two sources of Vitamin B.
Ans:
(i) Liver
(ii) Beans

 21. Write two sources of Vitamin C.
Ans:
(i) Orange/lime
(ii) Amla

 22. Write two sources of Vitamin D.
Ans:
(i) Fish
(ii) Butter

 23. What is roughage?  
Ans. The food containing plant fibres which sure also known as dietary fibres is called roughage.

24. What is the main Function of roughage?
Ans: The main function of roughage is to help our body get rid of undigested food.

25. Name some food items which provide roughage.
Ans: Whole grains, fresh fruits and vegetables are the main sources of roughage.

Class 6 Science Chapter 2 SHORT ANSWER TYPE QUESTIONS

1. What are nutrients? Name major nutrients.
Ans: The components of food which are needed by our body for growth and development are called nutrients. The major nutrients are:
(i) Carbohydrates
(ii) Fats
(iii) Proteins
(iv) Vitamins
(v) Minerals

2. What are the functions of carbohydrates?
Ans: They complete the energy requirements of the body so they are called energy providing food.

3. Write test for detecting the presence of starch.
Ans: Take a piece of the food item. Put 2-3 drops of dilute iodine solution on it. If the colour of the food item becomes blue-black, then it indicates the presence of starch in the food item.
(i) Food + Iodine — Blue-black colour (starch present)
(ii)  Food + Iodine — No blue-black colour (no starch present)

4. What are the functions of proteins?
Ans: Proteins are the most important nutrient. They are called body-building food. They help in the growth and repair of damaged cells and tissues of the body. They also help our body to fight against infections. Proteins make our nails, hair and muscles.

5. How can you test presence of proteins in a given food item?
Ans:Take a small quantity of the food item. If the sample is solid, grind it. Put some part of this in a clean test tube, add 10 drops of water to it and shake the test tube. Now, with the help of a dropper, add two drops of solution of copper sulphate and 10 drops of solution of caustic soda to the test tube. Shake well and place the test tube in test tube stand for a few minutes.
Observe colour of the contents of test tube. If colour of the contents turns violet, the food item contains protein.
Note: Copper sulphate and caustic soda solutions are harmful. Handle them with care.
Food + water + copper sulphate + caustic soda → violet colour → protein is present.

6. What are fats? Name some fat-containing substances.
Ans: The energy rich sources of food are called fats. They provide energy to the body. All types of nuts, mustard seeds, milk and butter are the major sources of fat. Like carbohydrates, fats also contain carbon, hydrogen and oxygen but fats contain less oxygen than carbohydrates.

7. Write test for detecting, presence of fat.
Ans: Take small quantity of the food item. Rub it on a piece of white paper. Observe carefully, you will find that the piece of white paper shows an oily patch on it which indicates that the food item contains fat.

8. What are vitamins? Write various kinds of vitamins.
Ans: They are protective compounds with no energy value. They help in proper body­ functioning and are required by the body in very small quantities. Various kinds of vitamins are—Vitamin A, Vitamin B-complex, Vitamin C, Vitamin D, Vitamin E and Vitamin K.

9. People who eat sea-food do not suffer from Goitre. Explain.
Ans: It is so because sea-food is a rich source of Iodine and Goitre is a deficiency disease caused due to lack of Iodine.

10. Excess intake of fats is harmful for the body because it causes obesity. Would it be harmful for the body to take too much of proteins or vitamins in the diet?
Ans. Yes, excess intake of proteins and vitamins in the diet is harmful and may lead to other diseases.

11. Name the vitamin that our body prepares in the presence of sunlight.
Ans: Vitamin D.

12. Name a vitamin that is not present in milk.
Ans: Vitamin C.

13. A patient had stunted growth, swelling on face, discolouration of hair and skin disease. Doctor advised him to eat a lot of pulses, grams, egg white, milk etc. What is wrong with the patient? Explain.
Ans:  The intake of protein is not enough in his diet and all these symptoms are caused due to deficiency of proteins.

14. A small child became very thin and lean and later he became so weak that he could not move. Which nutrients should he eat so as to improve his health?
Ans: Both carbohydrates and proteins.

15. What are the functions of minerals?
Ans: Minerals are protective part of foods occurring naturally and are needed by our body in small amount. Minerals are essential for proper growth of the body and to maintain good health. They do not provide energy. Milk, salt, eggs and green leafy vegetables are the main sources of minerals.

16. Write the functions of water in our body.
Ans: Water helps our body to absorb nutrients from the food. It also helps in removing the waste from the body in the form of urine and sweat. We get water from various types of liquids, fruits and vegetables.

17. What is obesity?
Ans: When a person eats too much fat-containing foods, then the fat gets deposited in his body and he may end up suffering from a condition called obesity.

18. What are deficiency diseases?
Ans: When a person eats such a food continuously for a long time which may not contain a particular nutrient, then this condition is called deficiency of that nutrient. Deficiency of one or more nutrients can cause diseases or disorders in our body. Such type of diseases are known as deficiency diseases.

Class 6 Science Chapter 2 LONG ANSWER TYPE QUESTIONS

1. List various types of nutrients and write the functions of each.
Ans. The various types of nutrients are:
(i) Carbohydrates: They are mainly energy-providing nutrients.
(ii) Fats: They provide energy for the body. They give much more energy than carbohydrates if consumed in same amount.
(iii) Proteins: They are called body-building foods. Proteins help in the formation and repairing of body parts. Skin, hair, muscles, enzymes are made up of proteins.
(iv) Vitamins: Vitamins help in protecting our body against disease. They also protect eyes, bones, teeth and gums.
(v) Minerals: Minerals are essential for proper growth of body and to maintain good health.

2. What is a balanced diet? Write the components of balanced diet.
Ans: A diet which provides the right proportion of all the nutrients that our body needs along with roughage and water is called balanced diet. The various components of balanced diet are carbohydrates, fats, proteins, vitamins, minerals, roughage and water.

 3. Prepare a chart to show various vitamins and minerals and the disorders caused by their deficiency.

NCERT Solutions

NCERT Solutions for Class 6 Science Chapter 5 Separation of Substances

Topics and Sub Topics in Class 6 Science Chapter 5 Separation of Substances:

Section Name	Topic Name
5	Separation of substances
5.1	Methods of separation

NCERT Solutions for Class 6 Science Chapter 5 Textbook Questions Solved

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 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?
Ans. Sugar can be separated from wheat flour by sieving. Due to difference in the size of particles, sugar will stay on sieve and wheat flour will pass through it.

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. Figure 5.12(a, b) shows the steps involved in using a filter paper. 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.

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 ______. 
(a) Salt is obtained from sea water by the process of ____________ .
(b) 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 ____________.
Ans.
(a) threshing
(b)filtration
(b) evaporation
(d) sedimentation and decantation

9. True or false?
(a) A mixture of milk and 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.
Ans.
(a) False
(b) False
(c) False
(d) 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 for Class 6 Science Chapter 5

Class 6 Science Chapter 5 VERY SHORT ANSWER TYPE QUESTIONS

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. How will you separate mango from a mixture of mango and apple?
Ans. By picking.

4. You are given a mixture of salt and sand. Can you separate them by picking?
Ans. No, we cannot separate them by picking.

5. Name the method used to separate the pieces of stone from grain.
Ans. Handpicking.

6. How can you separate grains from stalk?
Ans. We separate grains from stalk by threshing.

7. What types of material can we separate by using handpicking?
Ans. The materials having different size and colour can be separated by handpicking.

8. Name the other methods used to separate solid materials of different size.
Ans. Sieving.

9. Name the process used to separate heavier and lighter components of a mixture.
Ans. Winnowing.

10. Can the above stated method be used if both the components have same weight?
Ans. No, this method cannot be used.

11. What is evaporation?
Ans. The process of conversion of water into vapour is called evaporation.

12. Name the method by which we get salt from ocean water.
Ans. Evaporation.

13. Define condensation.
Ans. The process of conversion of water vapour into liquid form is called condensation.

14. Write opposite process of evaporation.
Ans. Condensation.

Class 6 Science Chapter 5 SHORT ANSWER TYPE QUESTIONS

l. What is mixture?
Ans. When two or more than two substances are mixed together in any ratio then it is called a mixture.

2. Write various methods of separation of components from their mixture.
Ans.

1. Handpicking
2. Threshing
3. Winnowing
4. Sedimentation
5. Decantation
6. Filtration
7. Evaporation
8. Condensation

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:

Class 6 Science Chapter 5 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 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.

NCERT Solutions