STD-6, CHAPTER - 4: SEPARATION OF SUBSTANCES, EXERCISE QUESTION ANSWERS

A.     FILL IN THE BLANKS.

1.      Housewives sometimes use the method of ______ to remove unwanted substances from eatables like rice and pulses.

Ans: handpicking

2.      Common salt is prepared on a large scale through the process of _____.

Ans: evaporation

3.      Separation of tea leaves from tea is done by a process called ______

Ans: Filtration

4.      The process of ______ can be used to increase the rate of sedimentation of the suspended particles in a solid-liquid mixture.

Ans: loading

5.      The method, used to separate the fine particles, suspended in a liquid, by rotating the mixture at high speed, is known as _____

Ans: Centrifugation

B.      MATCH THE FOLLOWING:

 

1.      Wind                                                           a. hand picking

2.      Chalk powder and water                        b. winnowing

3.      Oil and water                                            c. sedimentation

4.      Separating peas from cooked Pulao    d. filtration

5.      Muslin Cloth                                             e. separating funnel

6.      Camphor and Salt                                    f. sublimation

      Ans:

1.      Wind                                                           b. winnowing

2.      Chalk powder and water                        c. sedimentation

3.      Oil and water                                            e. separating funnel

4.      Separating peas from cooked Pulao    a. handpicking

5.      Muslin Cloth                                              d. filtration

6.      Camphor and Salt                                     f. sublimation

 

C.      TICK THE CORRECT OPTION.

 

1.      Which of the following is an example of a heterogeneous mixture?

(a)    Sugar in water       (b) Pebbles in rice          (c) an aerated drink        (d) salt in water

      Ans: pebbles in rice

2.      Which one of the following is not an example of a pure substance?

(a)    oxygen             (b) air         (c) copper          (d) carbon dioxide

      Ans: air

3.      The process of loading helps to-  

(a)   Slow down the rate of sedimentation

(b)   Speed up the rate of sedimentation

(c)    Speed up the rate of decantation

(d)   Slow down the rate of decantation       

       Ans: speed up the rate of sedimentation

4.      Transferring the clear liquid, into another container, leaving behind the residue, is called–

(a)    sedimentation                                  (b)  decantation

(c)    Condensation                                    (d)   crystallisation

      Ans: decantation

5.      A substance, that sublimes easily, is-

(a)   naphthalene                                     

(b)   salt

(c)    sugar

(d)   chalk

      Ans: Naphthalene

D.     ANSWER THE FOLLOWING QUESTIONS IN BRIEF.

 

1.      Name any three methods used for separating a solid-solid mixture.

Ans: Three methods used for separating a solid-solid mixture are, sieving, threshing, sublimation.

2.      What is winnowing? Give an example of a mixture whose components can be separated by this method.

Ans: Winnowing is a process in which lighter substance are separated from heavier substances with the help of wind energy. The lighter husk are separated from the heavier wheat grains by the process of winnowing.

3.      Some iron pins get scattered on the carpet when you are expecting guests. How can one collect all the pins in the shortest possible time?

Ans: By using a magnet we can take out the iron pins quickly.

4.      Name any three substances which sublime on heating.

Ans: Three substances that sublime on heating are, ammonium chloride, camphor and iodine.

5.      What is crystallisation? Name any three substances which can be purified using this technique.

Ans: Crystallisation is a process which separates a pure solid, in the form of its crystals, from a saturated solution. Salt, sugar and washing soda can be purified using this technique.

E.      ANSWER THE FOLLOWING QUESTIONS.

 

1.      Differentiate between a pure substance and a mixture. Give two examples of each.

Ans: Pure Substance: A substance consisting of only one kind of particles is called a pure substance. Ex- Oxygen, Copper

Mixture: Mixture consists of two, or more, substances mixed together in any proportion. Ex- milk, air

2.      State the difference between heterogeneous and homogeneous mixtures

Ans: Heterogeneous Mixture: A mixture, having different compositions, over its different parts is called as heterogeneous mixture.

Examples: mixture of sand in water, iron nails in sulphur powder

Homogeneous Mixture: A mixture, having the same composition, over all its parts is called as homogeneous mixture.

Examples: Alloys, soft drinks

3.      Can a mixture of iodine and camphor be separated by the sublimation method? Give reason for your answer.

Ans: i) Sublimation is a method to separate solids, which sublime (changes to gaseous form) easily from substances which do not sublime.

ii) In this case, iodine and camphor both will sublime on heating. So, it is not possible to separate these two by the process of sublimation.

4.      Why does the size of naphthalene balls, put in open, keep on reducing with time?

Ans: i) We know that, naphthalene sublimes (changes directly into gaseous form).

ii) When naphthalene balls are kept in open, they continue to absorb the heat from the surrounding and sublime. So, their size goes on reducing with time.

5.      After a dust storm, how does rain help in making air clear?

Ans: i) In a storm, the dust particles being lighter in weight float in the air, and we cannot see anything around us.

ii) After this, if rain occurs, the dust particles along with the water droplets become heavy and come down to earth surface. Thus the atmosphere becomes clear.

6.      Sawdust, mixed in water, cannot be separated by the sedimentation method. Why?

Ans: i) Sedimentation is a process in which substances mixed in water settle down (sink in it) after some time.

ii) But as sawdust is lighter in weight, it will float on the surface of water and will not settle down. So it is not possible to separate sawdust, mixed in water by the process of sedimentation.

7.      The filtration method cannot be used to separate sugar and salt mixed in water. Why?

Ans: i) Filtration is done to separate the insoluble solids mixed in water with the help of cotton cloth or filter paper.

ii) But as sugar and salt are soluble in water, they pass through the filter paper (or cotton cloth) and thus cannot be separated through the process of filtration.

8.      Describe the method of centrifugation using an appropriate example.

Ans: Centrifugation is used to separate the fine particles suspended in a liquid, by rotating the mixture at high speeds.

       Take the example of separating cream from milk. In this process the milk is churned (rotated at a high speed). The heavier particles (cream) tend to settle down at the bottom of the container while the lighter ones stay at the top.

STD-6, CHAPTER- 2: FOOD, EXERCISE QUESTION ANSWER

A.     FILL IN THE BLANKS.

1.      Living organisms need food to _________ and _______.

Ans: live and grow

2.      Vitamins A, D, E and K are soluble in ______, whereas Vitamin B and C are ______ soluble.

Ans: fat, water

3.       The deficiency of ________, in the diet, causes a disease called Beri-Beri.

Ans: Vitamin B

4.       Vitamin K helps in _______ blood.

Ans: clotting

5.      The dietary fibres constitute _________

Ans: roughage

B.      WRITE TRUE OR FALSE FOR THE FOLLOWING STATEMENTS.

 

1.Vitamins and minerals are body-building foods.                                                                     False

2. Our skin makes Vitamin E in the presence of sunlight.                                                          False

3.  Deficiency of phosphorous can lead to anaemia.                                                                   False

4.   We should eat food that has all its essential components in the right proportions.           True

5.    Kwashiorkor occurs due to the deficiency of fat in the diet.                                                False

 

C.      TICK THE CORRECT OPTION.

 

1.      When a drop of iodine solution was put on the cut surface of a potato, it turned blue-black in colour. This indicates the presence of–

(a)   Vitamin                      (b)  Fat

(c)    Protein                       (d)  Starch

      Ans: starch

2.      The deficiency of Vitamin A, in our diet, causes a disease known as–

(a)    Scurvy                               (b)  rickets

(c)     nightblindness                 (d) beri-beri

      Ans: nightblindness

3.      Iron is essential for–

(a)   Growth of teeth and bones                      

(b)   Formation of haemoglobin  

(c)    Functioning of the thyroid gland                  

(d)   Making muscles strong

      Ans: formation of haemoglobin

4.      A child, who has bow legs, is suffering from a deficiency disease, known as –

(a)   scurvy                      (b)  rickets

(c)    goitre                      (d)   anaemia

      Ans: rickets

5.      The deficiency of proteins, in the diet of children, can cause a disease known as–

(a)   marasmus                      (b) rickets

(c)    kwashiorkor                  (d) anaemia

      Ans: kwashiorkor

D.     ANSWER THE FOLLOWING QUESTIONS IN BRIEF.

 

1.      Name the important sources of our food.

Ans: The important sources of food are plants and animals.

2.      State the importance of carbohydrates in our diet.

Ans: Carbohydrates, in our diet, are a source of energy.

3.      Name the vitamin whose deficiency causes the disease of-

(a) nightblindness

(b) beri-beri

(c) scurvy

(d) rickets

Ans: (a) nightblindness – Vitamin A

(b)   beri-beri – Vitamin B

(c)    scurvy – Vitamin C

(d)   rickets – Vitamin D

4.      Name any three of the minerals needed by our body.

Ans: Three minerals needed by our body are, iron, iodine and calcium.

5.      State the role of calcium in our body.

Ans: Calcium helps to build healthy bones and teeth.

6.      Write the full forms of the terms PEM and PCM.

Ans: PEM – Protien Energy Malnutrition

PCM – Protein Calorie Malnutrition

E.      ANSWER THE FOLLOWING QUESTIONS.

 

1.      Name two sources of each of the following:

(a) Carbohydrates                            (b) Proteins

(c) Fats                                                (d) Roughage

(e) Vitamin A                                     (f) Vitamin C

Ans: (a) Carbohydrates – banana, litchi

(b)   Proteins -  soyabean, pulses

(c)    Fats – mustard oil, Butter

(d)   Roughage – green vegetables, whole grains

(e)   Vitamin A – cod liver oil, shark liver oil

(f)     Vitamin C – Lemon, Indian Gooseberry

2.      Describe one test each for detecting the presence of the following in food.

(a) Proteins

(b) Starch

(c) Fats

Ans: (a) Test for proteins

Materials required:

Mortar and pestle, test tube, dropper, concentrated nitric acid

Procedure:

Crush some bean seeds in a mortar and pestle. Make a suspension using water. Take a little of this suspension in a test tube. Very carefully, add a few drops of concentrated nitric acid to it.

Observation:

The colour of the suspension changes to yellow.

Conclusion:

Protein is present in bean seeds.

 

(b) Test for Starch

Materials required:

iodine solution, test tube, dropper, raw potato.

Procedure:

Take an unboiled raw potato and cut it into pieces. Add iodine solution on the cut surface of the potato with the help of a dropper.

Observation:

After adding iodine solution on the cut surface of the potato, it turned blue-black.

Conclusion:

Potato contains starch in it.

 

(c) Test for Fat

Materials Required:

White tissue paper, butter

Procedure:

Take butter and rub it on the dry tissue paper.

Observation:

A translucent mark appeared on the tissue paper after rubbing butter on it.

Conclusion:

Fat is present in butter.

3.      Why do we need proteins and how do they affect our health?

Ans: (i) Proteins help in building up the developing tissues of a growing child.

(ii) Proteins also take care of the ‘wear and tear’ of the body tissues at all ages.

 4.      A mineral ‘X’ is essential for the formation of a component ‘Y’, in the blood of a person. The function, of component Y, is to transport oxygen in the body.

The deficiency of mineral ‘X’, in the diet of a person, causes a disease Z. Identify X, Y and Z. Also mention the symptoms of disease Z.

Ans: X – Iron

Y – Haemogobin

Z – Anaemia

A person suffering from anaemia appears pale and weak. The body shows fatigue, loss of appetite, whitening of nails and swelling of hands and feet.

5.      Deficiency of iodine is more common in mountainous regions. Why?

Ans: The soil and water in mountainous region are poor in iodine. So, deficiency of iodine is more common in these regions.

6.      What is a balanced diet? Why should we take a balanced diet?

Ans: (i) A diet that contains all the nutrients in right proportion, is called a balanced diet.

(ii) A balanced diet is very important for the proper growth and development of the body.

(iii) It provides us energy, needed for metabolic activities of the body like respiration, circulation and digestion.

       (iv) It also helps us in preventing deficiency diseases. So, we should take a balanced diet.