STD-4, CHAPTER-10: WATER POLLUTION, EXTRA QUESTION ANSWERS

 1.      ‘Water is an important natural resource.’- justify this statement.

Ans: i) Water is essential for all living beings.

ii) It is a habitat for many plants aand animals.

iii) It is essential for the existence and survival of all plants and animals.

Thus, water is an important natural resource.

2.      Name the major source of water?

Ans: Rain is the major source of water.

3.      ______ is the purest form of water.

Ans: Rain water (when just formed)

4.      How does the rain water become impure?

Ans: As the rain water reaches the surface of the earth, it dissolves some harmful gases, dust, smoke particles and germs present in air. Thus, it gets impure.

5.      Name any two materials which can make rain water impure.

Ans: Dust and smoke particles which can make rain water impure.

6.      Define the term polluted water.

Ans: Water containing impurities is called polluted water.

7.      What is pollution of water?

Ans: The processes, which make water impure, result in pollution of water.

8.      State the human activities which can cause water pollution.

Ans: i) People wash their clothes and bathe in river water. Some people bathe their cattle in rivers.

ii) People throw domestic waste in rivers.

iii) Waste materials, and harmful chemicals from factories, are often dumped in river water.

iv) Solid waste material, from power plants, may be thrown into the river water.

v) Water, from drains and sewage, goes into rivers.

vi) The chemical fertilisers flow into lakes or rivers after getting mixed with rain water.

vii) Oil, spilled by tankers and oil wells, pollutes sea water.

9.      Which two pollutants are often dumped by the factories into the rivers?

Ans: Harmful chemicals and waste materials are often dumped by the factories into the rivers.

10.  State the effects of water pollution.

Ans: i) Poisonous chemicals, from factories, kill marine animals.

ii) Industrial, and agricultural, wastes increase the growth of micro-organisms in water. This can reduce the supply of oxygen for the aquatic animals.

iii) Aquatic plants and animals get infected by polluted water. When other animals eat these infected animals or plants, they also become sick.

iv) Drinking polluted water may cause diseases.

v) Using polluted water for irrigation, decreases the fertility of the soil and damages crops.

11.  Suggest some ways to reduce water pollution.

Ans: i) Wastes from factories and power houses should not be allowed to flow into rivers directly.

ii) Pipes, carrying sewage, should not be allowed to enter into wells or rivers.

iii) Water, from drains or sewage, should not be allowed to enter into wells or rivers.

iv) People should not wash clothes, or use soaps if they bathe, in rivers.

v) The use of chemical fertilisers should be minimised. Instead, natural manure should be used.