PSC- Elementary Science: Note of Chapter Three

PSC- Elementary Science: Note of Chapter Three-Part 1

PSC NotesIn this chapter, you can know about water cycle, polluted water, causes of water pollution, effects of water pollution, prevention of water pollution and water purification. I think this chapter is easy to learn. In this chapter, you have to learn more essay type questions than short questions. These answers are based on your main text, so these will be easy for you. Besides text questions, you get here more fill in the gaps and short answered questions. The chapter is divided into two parts-part 1 and part 2. In part 1 you get the essay type questions of text.

Water for life

Essay type questions of text
1. Explain water cycles with figures.
Ans: The water of ponds, canals, rivers and seas turns into vapours by the heat of the sun. Water vapours go up through the atmosphere, cool down and turn into small particles of water. The small particles of water gather at a place to form clouds and float in the sky. Then these drop down on earth as rains. When water particles in the cloud become extremely cold, the particles turn into ice and falls down on earth as hails. Rain water flows over the soil and mixes with river water.

Water CycleFigure: Water Cycle

Water vapours reach to the mountain peaks as clouds. There the cold atmosphere turns water droplets of the clouds into ice. In summer the ice melts into water due to the heat of the sun and flows down the slope of the hills. This leads to the creation of small rivers in the hills. The water of the rivers finally falls into the sea. This cyclic order in which water returns back is called a water cycle.

2. How will you prove that are always some water vapours in water?
Ans: Air contains some vapours all the time. To prove it, at first, we have to take a few pieces of ice in water a glass. After some time, we can see some drops of water outside the glass. Water inside the glass pot cannot come out.

water drops outside the glassFigure: Water drops outside the glass

The glass became cold due to the cold ice. Reaching cold surface water vapours of the air turned into water drops. From this experiment, we can realize that, there are always some water vapours in the air.

3. What are the main causes of water pollution?
Ans: Man pollutes water mixing different things in it through careless activities. The main reasons for water

pollution are given below:
1. Washing utensils and dirty clothes, bathing cattle, rotting raw jutes, excreting, throwing animal carcass etc. pollute water of ponds, marshes, canals and rivers.

2. Washing beds, clothes and excretions of patients suffering from cholera, dysentery, typhoid and diarrhea in ponds, marshes, canals and rivers pollute water with the germs of the diseases.

3. Throwing of wastes from mills and factories into water pollutes it since the wastes carry harmful substances.

4. The excess amount of insecticides used in agriculture is drained by rain water into marshes, canals and rivers and pollutes water.

5. Floods and tidal waves inundate villages and cities. The excretions of men, domestic animals and birds mix with water and pollute it. This polluted water mix with the water of ponds, wells and tube wells and makes the drinking water undrinkable.

6. Besides there are natural causes of Arsenic pollution. There is mineral of Arsenic down in the earth. When Arsenic comes in touch with the layer of water it mixes with the water and pollutes it.

4. How is water pollution prevented?
Ans: To prevent water pollution the causes of water pollution should be stopped.
1. We should not wash utensils, dirty clothes and bath our cattle in the water bodies.
2. We should not throw excretion, animal carcass etc. in the water bodies.
3. Stop throwing of wastes from mills and factories into water.
4. We should not use excess amount of insecticides in the fields.
5. Stop washing beds, clothes and excretions of patients suffering from cholera, dysentery, typhoid and cholera.

5. How is pond water purified to make it free from germs?
Ans: There are many ways to make pond water free from germs. But boiling is the best way to kill the germs properly.

1. Filtration: Water may be cleaned by filtration through a thin cloth or filter. This water is clean but not free from germs.

2. Sedimentation: If we keep river or canal water into a pitcher for a while and we will see sediments at the bottom of the pitcher. But the water in the upper part of the pitcher is clean. The process of separating clean water in this way called sedimentation. This water is not fully free from germs.

3. Purifying water with chemicals: Water may be purified by mixing it with alum, bleaching powder, halogen powder etc.

4. Boiling: Boiling is the best way to make water germ free. When water starts boiling it is to be heated more for twenty minutes to kill the germs in it. Water is then cooled and filtered to make it safe for drinking.

Click Below Link for Part2
PSC- Elementary Science: Note of Chapter Three-Part 2


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