Chapter 15 Air Around us
Question 1: What is the composition of air?Answer: Air consists of water vapour, oxygen, nitrogen, carbon dioxide, dust and smoke.
Question 2: Which gas in the atmosphere is essential for respiration?
Answer: Oxygen is the gas in the atmosphere that is essential for respiration.
Question 3: How will you prove that air supports burning?
Answer: Place two candles of the same length on a table. Light both the candles. Cover one of the candles with an inverted glass tumbler. We observe that the candle covered with a glass tumbler got extinguished after some time, whereas the other candle continued burning. The candle gets extinguished because the component inside of the glass tumbler, which supports burning, is limited. Most of the component is used up by the burning candle. However, the other candle is getting continued supply of air. This component of air, which supports burning, is known as oxygen.
Question 4: How will you show that air is dissolved in water?
Answer: Take some water in a glass or metal container. Heat it slowly on a tripod stand. Before the water begins to boil, we can see tiny bubbles on the inside of the container. These bubbles come from the air dissolved in water. When we heat the water, the air dissolved in it escapes. As we continue heating, the water itself turns into vapour and finally begins to boil.
Question 5: Why does a lump of cotton wool shrink in water?
Answer: A lump of cotton wool shrinks when immersed in water because air present in the cotton wool escapes. And therefore, the volume of the cotton wool decreases.
Question 6: The layer of air around the earth is known as ___________.
Answer: The layer of air around the Earth is known as Atmosphere.
Question 7: The component of air used by green plants to make their food, is ___________.
Answer: The component of air used by green plants to make their food, is carbon dioxide.
Question 8: List five activities that are possible due to the presence of air.
Answer:
→ Respiration for survival
→ Cloud Formation
→ Winnowing
→ Transpiration
→ Burning objects
Question 9: How do plants and animals help each other in the exchange of gases in the atmosphere?
Answer: In the process of photosynthesis, plants make their own food and oxygen is produced along with it. Plants also consume oxygen for respiration, but they produce more of it than they consume. That is why we say plants produce oxygen. The balance of oxygen and carbon dioxide in the atmosphere is maintained through respiration in plants and animals and by the photosynthesis in plants. This shows the interdependence of plants and animals.
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