Exercises
1. What is the composition of air?
2.
Which gas in the atmosphere is essential for respiration?
3. How will you prove that air supports burning?
4.
How will you show that air is dissolved in water?
5. Why does a lump of cotton wool shrink in water?
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Answers
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Answer:
1.The air in Earth's atmosphere is made up of approximately 78 percent nitrogen and 21 percent oxygen, and other gases.
2.Oxygen.
3.Cover the burning candle with a glass jar. After few minutes the candle is extinguished. As the supply of air is stopped due to glass jar the burning of candle is also stopped. This experiment proves that air supports burning.
4.lump of cotton wool has a lot of air trapped inside the space present in its fibers. When this lump of cotton is immersed in water, all the air is replaced by water. Due to this, the cotton lump shrinks down.
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Answer:
1. It's a mixture of different gases. The air in Earth's atmosphere is made up of approximately 78 percent nitrogen and 21 percent oxygen. Air also has small amounts of lots of other gases, too, such as carbon dioxide, neon, and hydrogen.
2.Oxygen gas in the atmosphere is essential for respiration.
3.Cover the burning candle with a glass jar. After few minutes the candle is extinguished. As the supply of air is stopped due to glass jar the burning of candle is also stopped. This experiment proves that air supports burning.
4.
Take some water in a glass or metal container like pan and heat it. Just before water begins to boil, you will notice some bubbles at the inner surface of the pan. These bubbles come from the air dissolved in water. This shows that air is dissolved in water.
5.A lump of cotton wool has a lot of air trapped inside the space present in its fibers. When this lump of cotton is immersed in water, all the air is replaced by water. Due to this, the cotton lump shrinks down.
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