STD-5, CHAPTER-10: AIR, EXTRA QUESTION ANSWERSS

 1.      Why cannot we see air?

Ans: Pure air is colourless. So, we cannot see air.

2.      We feel air only when it _____.

Ans: Blows

3.      Name the main components of air.

Ans: The main components of air are, nitrogen (nearly 78%), oxygen (nearly 21%), water vapour and small amounts (1%) of other gases like carbon dioxide, ozone, helium and hydrogen.

4.      Define Humidity.

Ans: The amount of water vapour present in air determines the humidity of air.

5.      Why is air necessary for animals?

Ans: i) All the animals, including human beings, need oxygen to live.

ii) They take oxygen from air through the process of breathing.

iii) The oxygen, present in air, is used to produce energy from the food that is eaten.

iv) Oxygen is also required for burning.

6.      _______ gas is breathed out by animals.

Ans: Carbon dioxide

7.      _______ gas is required for burning..

Ans: Oxygen

8.      ______ gas is used by plants during photosynthesis.

Ans:  Carbon dioxide

9.       Define photosynthesis.

Ans: Photosynthesis is the process by which green plants prepare their food in the presence of sunlight.

10.  How is the balance of oxygen and carbon dioxide in air, maintained in nature?

Ans: i) Animals and human beings use oxygen present in the air and give out carbon dioxide gas.

ii) Plants, on the other hand, consume carbon dioxide during photosynthesis in day time. They then give out oxygen.

iii) In this way, a balance of carbon dioxide and oxygen is maintained in the air.

11.  How is nitrogen important for plants?

Ans: i) Nitrogen helps in the rapid growth of plants.

ii) It also helps them to develop their fruits and seeds.

iii) It also increases the size and quality of their leaves.

Therefore, plants require nitrogen in large amounts.

12.  How do plants utilise atmospheric nitrogen?

Ans: i) Bacterias, present in the soil, help to convert the atmospheric nitrogen into nitrate or ammonium salts.

ii) These salts are taken in by plants to get the nitrogen needed by them.

13.  Plants use nitrogen to form ______ essential for their growth.

Ans: Proteins

14.  Define atmosphere.

Ans: The blanket of air surrounding us, which acts as a shield to protect us, is called as the atmosphere.

15.  State the two possible harmful effects of ultraviolet rays.

Ans: The ultraviolet rays can cause skin and eye diseases in animals and affect the growth of plants.

16.  Which layer protects us from the harmful ultraviolet rays of sunlight?

Ans: The ozone layer protects us from the harmful ultraviolet rays of sunlight.

17.  When is air said to be polluted?

Ans: When air contains impurities like dust, soot, germs or other harmful gases like carbon monoxide, oxides of nitrogen and sulphur, it is said to be polluted.

18.  Define the term ‘air pollutants’.

Ans: The impurities present in air, are called as pollutants.

19.  Name the two basic forms of air pollutants.

Ans: The two basic forms of air pollutants are, gaseous pollutants and solid pollutants.

20.  Name the gaseous pollutants.

Ans: Carbon monoxide, ozone, oxides of nitrogen and sulphur, are gaseous pollutants.

21.  Name some solid pollutants.

Ans: Smoke, dust and germs are solid pollutants.

22.  What are the causes of air pollution?

Ans: i) Dust raised from the ground during dust storms.

ii) Stone dust raised by crushing of stones in quarries.

iii) Smoke emitted by vehicles.

iv) Smoke from forest fires.

v) Smoke raised by burning of coal in powerhouses.

vi) Burning of wood, cowdung cakes, garbage, etc., in households and open places.

vii) Germs from coughing and sneezing.

23.  What are the effects of air pollution?

Ans: i) By breathing polluted air, we may suffer from various problems like suffocation, cough, headache and so on. Polluted air may also cause skin and eye diseases.

ii) Air pollution may also lead to acid rain.

iii) Presence of carbon dioxide and some other gases, in air, causes greenhouse effect.

24.  How acid rain is caused?

Ans: Gases, like oxides of nitrogen and sulphur, present in automobile exhausts, mix with rain water and forms acid rain.

25.  Why is ‘acid rain’ harmful?

Ans: i) Acid rain damages crops and reduces the fertility of soil.

ii) It can also damage monuments made of marbles.

26.  How greenhouse effect is helpful to us?

Ans: Greenhouse effect helps the earth to stay ‘suitably warm’.

27.  What leads to global warming?

Ans: If carbon dioxide and some other gases present in excess in air, their ‘increased greenhouse effect’ can cause an ‘extra increase’ in the average temperature of the earth, which leads to global warming.

28.  Why should we feel ‘worried’ about ‘global warming’?

Ans: global warming can result in an increase in the melting of polar ice-caps which can cause wide-spread damage and destruction.

29.  Suggest some ways of reducing air pollution.

Ans: i) We should plant more trees.

ii) We should use less vehicles.

iii) Regular check-up of vehicles.

iv) Use of cleaner fuels.

v) Dumping the garbage in a pit.

vi) We should construct tall chimneys.

vii) We should cover our nose and mouth while sneezing or coughing.

30.  How does planting of trees help in making air cleaner?

Ans: i) Plants use up carbon dioxide gas, present in the air, during the process of photosynthesis.

ii) This helps to reduce the greenhouse effect and maintain the earth’s temperature at a desirable level.

31.  Name some cleaner fuels.

Ans: LPG or biogas, CNG

32.  Why constructing tall chimneys is important for powerhouses and factories?

Ans: Powerhouses, and factories, should construct tall chimneys so that smoke coming out of them goes higher up in the atmosphere and is not inhaled by us.

33.  How can we minimise the use of vehicles?

Ans: i) We should use a bus or metro, if available, for going to the office instead of using a personal vehicle.

ii) We can also share, or ‘pool’, vehicles for going to the office.

This will reduce the number of vehicles on the road. As a result, the amount of smoke emission will also get reduced.