(i) By volume about _______ of air is nitrogen and about _________ is oxygen.
[78% ,21% ]
(ii) Incomplete burning of fuels produces ________ which is a _______ gas.
[carbon mono oxide, poisonous]
(iii) Carbon monoxide _________ the oxygen carrying capacity of the blood.
(iv) Petroleum refineries are a major source of gaseous pollutants like ______ and ______.
[sulphur dioxide and nitrogen dioxide.]
(v) _______ used in refrigerators damages the ozone layer of the atmosphere.
(vi) Ozone layer protects us from the harmful ________ rays of the sun.
[Ultra Violet ]
(vii) _______ of the world’s population is without safe drinking water.
(viii) We can save water by remembering the 3R’s ____, ____ and ________.
[Reduce, reuse and recycle]
(ix) Acid rain is formed by the oxidation followed by dissolution of ________ and gases in rain water.
Q.2. Define air pollution. What are air pollutants?
Ans: When air is contaminated by unwanted substances which have a harmful effect on both the living and
the non-living, it is referred to as air pollution. The substances which contaminate the air are called air pollutants.
Q.3. what are the various sources of air pollutants?
Ans: Natural sources like smoke and dust arising from forest fires or volcanic eruptions. Human activity like factories, power plants, automobile exhausts and burning of firewood and dung cakes.
Q.4. what is smog? Why is it harmful?
Ans: A thick fog-like layer in the atmosphere, especially during winters. This is smog which is made up of smoke and fog. The smog causes breathing difficulties such as asthma, cough and wheezing in children.
Q.5. What is acid rain?
Ans: Sulphur dioxide and nitrogen dioxide react with the water vapour present in the atmosphere to form sulphuric acid and nitric acid. The acids drop down with rain, making the rain acidic. This is called acid rain.
Q.6 How is the Taj Mahal affected by air pollution?
Ans: Pollutants in air are discolouring its white marble.
Q.7 What is meant by ‘Marble Cancer’?
Ans: Acid rain corrodes the marble of the monument. The phenomenon is also called “Marble cancer”.
Q.8 Write the full forms (i) CFC (ii) CNG (iii) LPG (iv) WWF
Ans:(i) chlorofluorocarbons(ii)Compress natural gas(iii) Liquefied petroleum gas(iv) World Wide Fund
Q.9 what is greenhouse effect? Name four greenhouse gases.
Ans: A part of the radiation that falls on the earth is absorbed by it. The trapped radiations further warm the green house earth. This is called the greenhouse effect. CO2 ,CH4 , N2 O, SO2
Q.10 Write a note on global warming.
Ans: Greenhouse gases like CO2 traps Sun’s heat and does not allow it to escape into space. As a result, the average temperature of the earth’s atmosphere is gradually increasing. This is called global warming.
Q.11 What is Van Mahotsav?
Ans: Van Mahotsav is an annual tree-planting festival in India, celebrated in the first week of November.
Q.12 Why does the increased level of nutrients in the water affect the survival of aquatic organisms?
Ans: The increased level of nutrients in the water, enhance the growth of algae in the water body. Once the algae dies, they serve as food for decomposers like bacteria. For the decomposition, a lot of O2 in the water body decreases and may kill aquatic organisms.
Q.13 Why do we say that the river Ganga is dead at many places?
Ans: This is because the pollution levels are so high that aquatic life cannot survive.
Q.14 What is potable water?
Ans: Water which is suitable for drinking is called potable water
Q.15. What are the various methods by which water can be made safe for drinking?
Ans: The various methods by which water can be made safe for drinking are: (a) Using candle type filter (ii) boiling (iii) by adding chlorine tablets or bleaching powder to the water