psc-elementary Science-note

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

Air, it’s your fourth chapter. In this chapter, you can know the ins and outs about air. According to my opinion, you get here more essay type questions than the short questions and this chapter is easy to learn. This chapter is related to the previous two chapters. This chapter has been divided into two parts- part 1 and part 2. In part 1,
you get essay type questions and short answered questions of the text.

Air

Essay type questions of text
1. What are the works where flow of air can be used?
Ans: Flow of air can be used in many works.
1. The flow of air is used to rotate big wheels or turbines to generate electricity.
2. Flow of air is also used to clean crops from dirt and hoist sails of boats.
3. We dry our clothes by the flow of air.
4. We feel comfortable in summer when wind blows and touches our body.
5. We use hand fan and electric fan for blowing air to keep our body cool.

2. Discuss how air is polluted?
Ans: Air is mainly polluted by the activities of man.
1. Black smoke from brick fields, mills and factories, buses, trains, tempos and baby taxies pollutes air.
2. Air becomes polluted if carbon dioxide increases in the air. The burning of coal, petroleum, and natural gas is the reason for increases of carbon dioxide in air.
3. The smoke of bidi and cigarettes pollutes air.
4. When a patient of tuberculosis or pox sneezes or coughs, he also spreads germs into air and pollutes it.
5. Excreting and throwing garbage carelessly anywhere spreads foul smell and pollutes air.
6. Air is also polluted by small dust particles during construction of houses, roads and highways.

*3. Explain how the elements of air help us to live?
Ans: Air mainly contains nitrogen, oxygen, carbon dioxide and water vapours.
1. Oxygen: When we breathe we take oxygen from air. Oxygen breaks down the foods we eat and creates energy. Fish lives on taking oxygen from the air contained in water. We cannot build fire without oxygen. We cook our foods and boil water using fire.

2. Nitrogen: Nitrogen is used to produce Urea. This nitrogen is used to preserve different kinds of foods such as fish, meat, fruits, chips etc. in tins or packets.
3. Carbon dioxide: Carbon dioxide is mixed under high pressure with the soft drink of the bottle. This gives a sharp taste to the drink. This gas is used to extinguish fire.
4. Water Vapours: Water vapours help to build cloud, to dry clothes.

4. Write the steps to be taken to prevent air pollution?
Ans: Prevention of air pollution is important to keep us safe from the harmful effect of air pollution. Air pollution may be prevented by taking the following steps:
1. Stop use of vehicles which produce black smokes.
2. Construct brick fields away from human habitations.
3. Develop new technology which uses less fuel.
4. Stop smoking, especially near others or in closed places.
5. Use hearth or cooker of improved quality.
6. Conserve forests.
7. Plant trees of new forestation.

5. Why is smoking harmful?
Ans: Smoke is one of the main causes of air pollution. The smoke suffocates man if he goes near it. Black smoke contains carbon monoxide, carbon particles and carbon dioxide. Carbon monoxide is very poisonous. These are harmful to our health. The smoke of bidi and cigarettes pollutes air. Especially if anybody smokes in a closed room he does more harm to other people in the room.

Short answered questions of text
1. Write the names of four elements of air?
Ans: The four elements of air are: nitrogen, oxygen, carbon dioxide and water vapours.

2. What is acid rain?
Ans: When coal is burnt the sulphur in the coal burns and produces sulphur dioxide. The oxide of sulphur mixes with rain water and makes it acidic. This rain is called acid rain.

3. How can air pollution in the kitchen be decreased?
Ans: A hearth or a cooker is another source of producing carbon dioxide. Air pollution in the kitchen can be
decreased by taking the following steps:
1. Use hearth or cooker of improved quality.
2. Use proper ventilation in the kitchen.

4. How can the effects of pollution by brick fields be decreased?
Ans: Black smoke from brick fields contains carbon monoxide, carbon particles and carbon dioxide. The following steps can be taken to decrease the effects of pollution by brick fields.
1. Construct brick fields away from human habitation.
2. Develop new technology which uses less fuel.

5. What are the places where air does exist?
Ans: Air surrounds us from all sides. The air that surrounds us is called atmosphere. Earth soil contains air in the small spaces between the granules. There is air in water also, mixed in it. Air is an important element of environment.

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