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  1. The main function of fats in the body is to provide energy. By supplying energy, fats save proteins from being used for energy and allow them to perform their more important role of building and repairing tissues. Fats on oxidation provide almost twice as much energy as that given by carbohydrates. The fats provide on oxidation about 37 kJ of energy per gram as compared to about 17 kJ of energy per gram of carbohydrates. Fats yield more energy than carbohydrates because fats contain less percentage of oxygen and higher percentage of carbon and hydrogen as compared with carbohydrates. Fats can also be stored in body for subsequent use. When we consume food which has more energy than is required by the body for performing various functions, the excess food is deposited under our skin in the form of subcutaneous fat.
  2. In addition to supplying energy, fats also help in forming structural material of cells and tissues such as the cell membrane.
  3. Fats also carry the fat soluble vitamins A, D, E and K into the body and help in the absorption of these vitamins in the intestines.
  4. Fat stored under skin protects animals from cold because it is poor conductor of heat.



  • Fats and oils are triesters of glycerol with long chain fatty acids.
  • Animal fats are rich in saturated fats whereas vegetable oils are rich in unsaturated fats.
  • Fats and oils are insoluble in water but are soluble in organic solvents such as benzene, hexane, ether, petroleum ether, etc.
  • Saponification. The alkaline hydrolysis of fats and oils is called saponification. The products of saponification are glycerol and sodium or potassium salts of long chain fatty acids (soaps).
  • Hydrogenation of oils transforms them into fats.
  • Oil can be extracted from plant seeds by pressing and solvent extraction.
  • Soaps. These are sodium or potassium salts of long chain fatty acids.
  • Synthetic Detergents. These are sodium salts of long chain benzene sulphonic acids or long chain alkyl hydrogen sulphates.
  • Synthetic detergents can be used in acidic medium or in hard water.
  • The cleansing action of soaps and detergents is based on the presence of both hydrophobic and hydrophilic groups in their molecules which helps to emulsify the oily dirt which can then be rinsed out.


I. Objective Type Questions

Select the most appropriate choice from the options given as (a), (b), (c) and (d) after each question:

1.      Fatty acids are

a)      Unsaturated dicarboxylic acids

b)      Long-chain alkanoic acids

c)      Aromatic carboxylic acids

d)     Aromatic dicarboxylic acids

2.      Fats and oils are

a)      monoesters of glycerol

b)      diesters of glycerol

c)      triesters of glycerol

d)     diesters of glycol

3.      Liquid oils can be converted to solid fats by

a)      Hydrogenation

b)      Saponification

c)      Hydrolysis

d)     Oxidation of double bonds.

4.      Alkaline hydrolysis of oils and fats is known as

a)      Saponification

b)      Rancidification

c)      Diazotization

d)     Hydrogenation

5.      Sodium or potassium salts of fatty acids are known as

a)      Carbohydrates

b)      Soaps

c)      Non-soapy detergents

d)     Proteins.


II. Fill in the Blanks

6.      Complete the following sentences by supplying appropriate words:

i.            Triglycerides containing unsaturated fatty acids are        ………. at room temperature and are called ……….

ii.            The products of saponification of fats are soaps and       ……….

iii.            Hard soaps are      ………. salts of long chain fatty acids.

 III. Discussion Questions

7.      What are fats and oils? How do they differ from each other?

Is it possible to convert oil into fat?

8.      Give structure of a saturated fat and an unsaturated fat.

9.      Write down the structure of

i.            propane-1, 2, 3-triol

ii.            hexadecanoic acid

iii.            sodium octadecanoate.

10.  What are the various steps involved in the extraction of oil from groundnuts?

11.  What are the uses of fats and oils?

12.  What are the major functions of fats and oils in the human body?

13.  What is a detergent? Name two types of detergents.

14.  What are soaps? Why does it not produce lather easily in hard water?

15.  What are hard and soft soaps?

16.  What is the basic structure of a soap molecule?

17.  Why is sodium chloride added during the manufacture of soap from oils?

18.  Why is soap not suitable for washing clothes when water is hard?

19.  How do synthetic detergent differ from soaps? What is the basic structure of a synthetic detergent molecule?

20.  Why are synthetic detergents called soapless soaps?

21.  What are synthetic detergents? Give one example of a synthetic detergent.

22.  What are the advantages of synthetic detergents over soaps?

23.  How is soap prepared in laboratory?

24.  Name the raw materials required for the manufacture of soap.

25.  What are the advantages of synthetic detergents?

26.  Explain the cleansing action of soap.

27.  Explain why detergents are preferred over soaps?

28.  Explain the water pollution by the use of synthetic detergents.

29.  Name the two ways by which soaps or detergents help in cleansing.

30.  Would you be able to check if water is hard by using a detergent?



I.   Objective Type Questions

1.      (b)

2.      (c)

3.      (a)

4.      (a)

5.      (b)

II.   Fill in the Blanks

6.      (i) liquid, oils

(ii) glycerol

(iii) sodium