PSC- Elementary Science: Note

PSC- Elementary Science: Note of Chapter Four -Part 2

Yes, you are right. This is the second part of the note of chapter four. Here, you get more questions and fill in the blanks. You can see a star symbol before some questions, which seem to me more important. I tried to give attention to every line, so if you go through all questions, I think you will be able to give answer any question, whether will come from this chapter.

Air

More questions
*1. What is atmosphere?
Ans: The air that surrounds us is called atmosphere.

2. How do we take oxygen?
Ans: When we breathe we take oxygen.

3. What does oxygen do? Or, Why do we need oxygen?
Ans: Oxygen breaks down the foods we eat and creates energy.

*4. Why do we need oxygen?
Ans: Energy keeps our body warm.

*5. How does fish live in water?
Ans: Fish lives on taking oxygen from the air contained in water.

6. Give some examples of using air?
Ans: We use air in different ways:
1. We cannot build fire without oxygen. We cook our foods and boil water using fire.
2. We burn fuels to run mills and factories, drive vehicles, generate electricity.
3. The flow of air is used to rotate big wheels or turbines to generate electricity.
4. Flow of air is also used to clean crops from dirt and hoist sails of boats.

7. How does air help us in communication system? Or, How do the things filling with air give us benefit?
Ans: The wheels of bicycles, rickshaws and cars are filled with air. This helps bicycles, rickshaws and cars to move fast. Riding bicycles and rickshaws become easy.

*8. Where is less oxygen?
Ans: There is less oxygen on peaks of mountains.

9. When patients are given with oxygen from cylinders?
Ans: Patients with breathing problems are given oxygen from cylinders.

*10. Why drivers carry oxygen cylinder?
Ans: We cannot breathe under water. This is why drivers carry oxygen cylinders to stay under river or sea water for a long time in search of things.

11. Why is Urea used?
Ans: Urea is used for the growth of plants.

*12. Write the uses of Nitrogen?
Ans: Nitrogen of the air 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.

*13. Why is carbon dioxide mixed with soft drink?
Ans: Carbon dioxide is mixed under high pressure with the soft drink of the bottle. This gives a sharp taste to the drink.

14. Why we rotate the big wheels or turbines?
Ans: To generate electricity we rotate big wheels or turbines.

15. Why do we dry our wet clothes in the sun and open places?
Ans: Water turns into vapour in air because of heat from wet clothes in open places.

16. What is air pollution?
Ans: Many things may mix with air in different ways. The quantity of the elements of air may also increase or decrease for different reasons. If there is any change in the natural composition of air it becomes harmful to us.
The change in the natural composition of air is called air pollution.

17. Why do we feel cold when wind blows and touches our body?
Ans: Flows of air absorbs heat. So we feel cold when wind blows and touches our body.

*18. What does smoke contain?
Ans: Smoke contains carbon dioxide, carbon particles and carbon monoxide.

*19. Which gas is very poisonous?
Ans: Carbon monoxide is very poisonous.

*20. Which diseases can be caused by air pollution?
Ans: Polluted air creates problems of respiration and different diseases in the body. A man may be attacked by fatal diseases such as allergy, cough, asthma, bronchitis, high blood pressure, headache, lung cancer etc. due to polluted air>

*21. How does fire extinguisher equipment work?
Ans: Fire is not ignited without oxygen. If there is a fire anywhere carbon dioxide is sprayed there from this equipment. This gas is heavier than air. So the gas forms a cover on the fire. Thus oxygen cannot come in contact to the fire and the fire is extinguished.

Fill in the blanks
1. Air surrounds us from all sides.
2. Energy keeps our body warm.
3. We cannot build fire without oxygen.
4. Carbon dioxide is heavier than air
5. Flow of air absorbs air.
6. We use hand fan and electric fan for blowing air to keep our body cool.
7. The smoke suffocates you if you go near it.
8. Air is mainly polluted by the activities of man.

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