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Class–VI (CHAPTER-15) AIR AROUND US, Questions, , 1. What is the composition of air?, 2. Which gas in the atmosphere is essential for respiration?, 3. How will you prove that air support burning?, 4. How will you show that air is dissolved in water?, 5. Why does a lump of cotton wool shrink in water?, 6. The layer of air around the earth is known as --------------., 7. The component of air used by green plants to make their food, is -----------., 8. List five activities that are possible due to the presence of air., 9. How do plants and animals help each other in exchange of gases in the atmosphere?

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Class–VI (CHAPTER-15) AIR AROUND US, Answers, , 1. Air contains some gases, water vapour and dust particles. The gases in air includes, nitrogen, oxygen, small amount of carbon dioxide and many other gases. The gases, that make up maximum proportion are nitrogen (78%) and oxygen (21%)., Remaining 1% us constituted by carbon dioxide and few other gases, water vapour, and dust particles., 2. Oxygen, 3. Two lighted candles are taken. One candle is fixed in a tumbler containing water., This candle is covered by an inverted glass. After sometime, the covered candle gets, extinguished and water rises up to 1/5th in one of the glass. This shows that oxygen, is necessary for burning because 1/5th is oxygen. The candle was extinguished as, soon as all the oxygen was used up., 4. When a tumbler containing water is heated, tiny bubbles appear on the inner side., These bubbles appear before the water starts boiling. So, these must be air bubbles., This shows that water contain air., 5. A lump of cotton wool shrinks in water because the air inside wool cotton is driven, out by water. The layers stick together and hence lump shrinks., 6. Atmosphere, 7. Carbon dioxide., 8. Activities due to presence of air:, (i), , Winnowing, , (iv), , Photosynthesis, , (ii), , Formation of clouds, , (v), , Transpiration, , (iii), , Respiration, , (vi), , Flying of birds, , 9. In photosynthesis, plants take carbon dioxide and give out oxygen. The animals, breath in oxygen in respiration and carbon dioxide is given out which is again used, by plants for photosynthesis, that is, preparation of food by plants., This is how plants and animals help each other in the exchange of gases in the, atmosphere.