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5. Explain the differences between pure air and polluted air., Soln:, , , , The composition of pure air contains 78% nitrogen, 219% oxygen and 0.03% carbon dioxide. Besides these, there, are some other gases like methane, argon, ozone and water vapors’. The air is said to be polluted when the, composition of air is altered by the addition of harmful substances or gases such as sulphur dioxide, carbon, monoxide, nitrogen dioxide and particulate matter., , 6. Explain circumstances leading to acid rain, How does acid rain affect us?, Soln:, , Sulphur dioxide and nitrogen dioxide are the type of pollutants, which are released into the atmosphere by the, burning of fossil fuels like diesel and coal. These pollutants react with the water vapours present in the, atmosphere to form nitric acid and sulphuric acid respectively. By precipitation, these acids come down and form, the acid rain., , Effects caused by the acid rain:, , a) It destroys the crops., b) Harmful for the building especially to those made of white marble like the Taj Mahal., , 7. Which of the following is not a greenhouse gas?, (a) Carbon dioxide, , (b) Sulphur dioxide, , (c) Methane, , (d) Nitrogen, , Soln:, , Answer is (d) Nitrogen, , 8. Describe the ‘Green House Effect’ in your own words., Soln:, , The greenhouse effect is the cause of global warming, i.e. overall increase in the temperature of the Earth. The, greenhouse gases cause the greenhouse effect. Examples of greenhouses gases include methane, CO) and water, vapour. When solar radiation reaches the Earth, some radiations are absorbed by the Earth and then released back, to the atmosphere. Greenhouse gases present into the atmosphere trap these radiations and do not allow the heat to, leave. This helps our planet in keeping warm and thus helps in human survival. However, an indiscriminate, increase in level of greenhouse gases, it can lead to an excessive increase in the Earth’s temperature leading to, global warming.