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Short Note, , What is atmosphere?, , The earth is surrounded by a thick layer of, air called the atmosphere that extends, upto a height of about 320 kilometres, , above the surface of the earth., , Why can't we see air?, , We can't see air because it is colourless,, , odourless and transparent gaseous matter., , What is wind?, , Fast-moving air is called wind., , What would have happened if there would, , have been no atmosphere around the, , aarth?

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Ne MAT Gi., , Without an atmosphere, life would not be, possible as the atmosphere protects us, from harmful gases. We could not live, without air present in the atmosphere. In, the absence of the atmosphere, the earth, would get so cold at night that we would, not be able to survive. No CO2 and N2 for, , plants without atmosphere., , Why is air called a mixture? Give five facts, , in support of your answer., , Air is a mixture because:, , 1. Air has no formula, a mixture has no, formula whereas the compound has a, formula., , 2. No energy changes are involved to, form air from various gases., , 3. When air is formed out of its

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constituents no change in mass and, no change in volume takes place., , 4. Properties of air vary from place to, place and from time to time. i.e. there, , is more COz in towns as compared to, , villages where more oxygen prevails, , as compared to towns., , 5. Components of air can be separated, , by simple physical methods., , What are the main components of air?, , Main components of air are:, , 1. Nitrogen, 2. Oxygen, , Write down the composition of three main, , gases present in air by volume., , Camnacitinn of air hy voaliima

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OE EE EEO EE ee —, , Nitrogen 78%, Oxygen 21%, Carbon dioxide 0.03-0.04%, Inert gases 0.9%, Water vapours’ Variable, Bust particles Variable, , Other impurities Variable, , What do you observe when Ice cold water, , is filled in a glass tumbler., , We will observe that fine water droplets get, deposited on the outer wall of the glass, , tumbler., , What do you observe when burning candle, , is covered with an inverted jar.

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The candle burns more brightly because, , the candle gets oxygen support in burning., , What do you observe when Carbon dioxide, , gas is passed through lime water., , When COg gas is passed through lime, , water it forms calcium carbonate which is, white precipitate (turbidity). This gives the, milky white appearance to the solution., , What do you observe when a beam of light, is allowed to enter in a closed dark room, , through a small hole., , We will observe randomly moving dust, particles in the beam of light. This, confirms the presence of dust particles in, , the air.