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“”“, , , , Chapter 15: Air Around Us, , A., , f, , Tick (/) the correct options., 1. (b) 2. (c) 3. (b) 4. (a), Fill in the blanks., , 1. respiration 2. wind 3. mixture 4. carbon dioxide, 5. Windmill, , Match the following., , 1. (f) 2. (d) 3. (b) 4. (e) 5. (a) 6. (c), Very Short Answer Questions., , 1. Humidity is the amount of water vapour present in air., , 2. Carbon dioxide 3. Oxygen, , 4. Smoke and dust particles 5. Atmosphere, , 6. Underground animals get oxygen for breathing from the air present, between the soil particles., , Short Answer Questions., , 1. The blanket of air that surrounds the earth is called atmosphere. The, major components of air are nitrogen, oxygen, carbon dioxide and a few, other gases, water vapour and dust particles., , 2. (a) The doctor provides extra oxygen to Priyanka’s uncle by using an, , oxygen cylinder., (b) This shows her caring nature and ability to take quick decisions., , 3. Some variations in the composition of air from place to place are:, , (i) The air over industrial areas usually has a higher amount of carbon, dioxide and dust in it than the air over open spaces., , (ii) In coastal areas, air has more water vapour than in areas away from, the coast., , aueenss = -—08 © Mew -- - - _, , 4. The air is useful to us in many ways. Its two uses are :, , (i) Oxygen present in air is used by all living organisms for respiration., (ii) Wind helps in the dispersal of seeds of plants. It also helps in, pollination., , 5. Two ways by which we can reduce air pollution are:, , {i) Planting as many trees as possible., (ii) Using cleaner fuels like CNG in vehicles instead of petrol and diesel., , 6. We should breathe through nose because the fine hair and mucus, present inside the nose prevent dust particles from entering our lungs., if we breathe through mouth, harmful dust particles and germs may, enter our body and affect our health., , Long Answer Questions., , 1, Animals inhale oxygen from air and exhale carbon dioxide which goes, into the air. The burning of fuels, uses oxygen from the air and gives, out carbon dioxide. Green plants use carbon dioxide from the air for, the process called photosynthesis during day and give out oxygen. The, process of respiration in plants takes place during day as well as night., But during day, the oxygen released during photosynthesis is more than, the oxygen used in respiration. Therefore, the oxygen is released in, the atmosphere is consumed by animals for respiration. In the above, mentioned ways, plants and animals maintain the balance of oxygen, , and carbon dioxide in the air.

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F., , ee cee ee SS rave, , Long Answer Questions., , i, , Animals inhale oxygen from air and exhale carbon dioxide which goes, into the air. The burning of fuels, uses oxygen from the air and gives, out carbon dioxide. Green plants use carbon dioxide from the air for, the process called photosynthesis during day and give out oxygen. The, process of respiration in plants takes place during day as well as night., But during day, the oxygen released during photosynthesis is more than, the oxygen used in respiration. Therefore, the oxygen is released in, the atmosphere is consumed by animals for respiration. In the above, mentioned ways, plants and animals maintain the balance of oxygen, and carbon dioxide in the air., , To show the presence of air in water, , Things needed: A beaker, tripod stand, a Bunsen burner, some water., Method: Take some water in a beaker and keep it on a tripod stand., Heat the water slowly by using a Bunsen burner., , You will observe that, much before the water begins to boil, tiny bubbles, appear on the inner side of the beaker. These bubbles come from the air, dissolved in water. Actually, when water is heated, the solubility of air in, it decreases. As a result, the air dissolved in water comes out in the form, of tiny bubbles., , When the dissolved gas gets removed through heating and the same, water is heated again after a short interval of time, we do not observe, bubbles. On further heating, the water itself turns into vapour and, finally begins to boil. It shows that air is present in water., , aw. « , let, «We. i ec et ae ee