Something to Know
A. Fill in the blanks.
1. Rain water is the purest form of water.
2. Water containing impurities is called polluted water.
3. Chemical fertilisers and pesticides used by farmers, can cause water pollution.
4. Drinking polluted water can cause diseases like diarrhea and jaundice.
5. Industrial and agricultural wastes increase the growth of micro- organisms in water.
B. Write True or False for the following statements.
1. River water is the purest form of water. False
2. Polluted water may contain dust, germs and smoke. True
3. Throwing domestic waste, in rivers, causes water pollution. True
4. Increased growth of micro-organisms in water increases the amount of oxygen for aquatic animals. False
5. Use of chemical fertilisers helps in preventing water pollution. False
C. Tick (✔) the correct option.
1. A disease that may be caused by drinking polluted water is-
(a) malaria
(b) cough
(c) cholera (✔)
(d) dengue
Answer – (c) cholera (✔)
2. Polluted water should not be used for irrigation because-
(a) it can harm aquatic animals
(b) it pollutes river water
(c) it reduces fertility of soil (✔)
(d) it increases the production of crops
Answer – (c) it reduces fertility of soil (✔)
3. Oil spills in the sea are harmful because they-
(a) decrease the level of water in sea
(b) infect the aquatic plants
(c) increase the growth of micro-organisms in water
(d) cut off the supply of oxygen for aquatic animals (✔)
Answer – (d) cut off the supply of oxygen for aquatic animals (✔)
4. Pollution of river water can be reduced if-
(a) chemical fertilisers are used for increasing production of crops
(b) farmers use sprinklers for irrigating their fields
(c) water is allowed to stagnate around the river banks
(d) people do not wash clothes or bathe their cattle in rivers (✔)
Answer – (d) people do not wash clothes or bathe their cattle in rivers (✔)
D. Answer the following questions in brief.
1. Name any two materials which can make rain water impure.
Answer – Two materials which can make rain water impure are –
Harmful gases.
Dust particles
2. Name any two human activities which can cause water pollution.
Answer – The two human activities which can cause water pollution are-
Washing clothes and bathing cattle in river.
Throwing industrial waste in water river.
3. Which two pollutants are often dumped by the factories into the rivers?
Answer – Waste materials and harmful chemicals are often dumped by the factories into the rivers.
4. Name any two diseases that may be caused by drinking polluted water.
Answer – The two diseases that may be caused by drinking polluted water are-
Typhoid
Cholera
5. Write the names of two types of materials, used by farmers, to increase the production of crops.
Answer – The farmers use chemical fertilisers and pesticides to increase the production of crops.
E. Answer the following questions.
1. How do wastes, from factories and fields, affect the aquatic animals?
Answer – Waste from factories increases the growth of microorganism in water. This reduces the supply of oxygen for the aquatic animals.
2. How can polluted water affect the crops?
Answer – When polluted water is used for irrigation, the fertility of soil gets reduced and crops can get damaged.
3. Why are oil spills harmful for marine life?
Answer – Oil spills form a cover on the surface of water. This cuts off the supply of oxygen to the animal living under water. This is why it is harmful for marine life.
4. State any four effects of water pollution.
Answer – The four effects of water pollution are –
Poisonous chemicals from factories kill marine animals.
Polluted water reduces the fertility of soil.
Aquatic plants and animals get infected by polluted water.
Drinking polluted water cause diseases like typhoid, diarrhea, cholera etc.
5. State four ways of reducing water pollution.
Answer – Four ways to reduce water pollution are-
People should not wash their clothes in rivers.
Waters from drains should not be allowed to enter rivers.
Industrial waste should not be allowed to flow into rivers.
Use of chemical fertilisers should be minimised.
Value Based Question
On Ria’s birthday, her grandparents arranged a ‘pooja’ at home. Ria participated in the ‘pooja’ with full devotion. Next day, Ria’s parents put the flowers and other materials, used in the pooja’, in a polythene bag. On being asked by Ria, her parents told her that they were going to immerse the used ‘pooja’ materials in the holy river flowing across the city. Ria remembered her science lesson in the school where her teacher had told her about the ways in which water gets polluted. She politely shared her thoughts with her parents. Her parents felt happy about their daughter’s concern for environment and did not put the used ‘pooja’ materials in the river.
1. State the values displayed by Ria.
Answer – Values displayed by Ria are-
Environmental conscious.
Confident
Responsible
2. Suggest some ways of disposing off the ‘pooja’ materials.
Answer – Ways of disposing off the ‘pooja’ materials are –
Fruit, flowers and leaves can be disposed in garden or to compost bin.
Plastic materials or idols can be given away for recycle.
Sweets and offerings should be distributed in poor people.
Something to Do
1. Make a collage showing various ways in which water gets polluted.
Answer –
2. Make posters, and write slogans, on prevention of water pollution. Display them in the school.
Answer –
3. Read the hints given below and fill the boxes in the crossword puzzle with suitable words.
Down↓
1. They increase the production of crops but cause water pollution.
3. This material may be present in polluted water.
5. Oil spills reduce the supply of this gas for aquatic animals.
Across →→
2. It is the name of a disease caused by drinking polluted water.
4. This water, when mixed with rivers or wells, makes them polluted.
