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Science [ 3 Marks Questions ]

T2 CH4 Air · Tamil Nadu Board STD 6 (Tamil - English Medium). 3 questions.

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[ 3 Marks Questions ]

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Question 13 Marks
Can you guess why fire extinguishers throw a stream of carbon-di-oxide while putting - off the fire?
Answer
The reasons behind fire extinguishers throw a stream of CO while putting off fire:-
  1. $CO _2$ is a colorless and in normal concentrations, odorless gas. It doesn't react with burning materials, so it doesn't create any toxic or other by-products while putting off the fire.
  2. Carbon dioxide doesn’t conduct electricity, making it an ideal fire suppressant for use in places where a large amount of electricity may be present.
  3. $CO _2$ acts on fires in two ways: The release of the gas under pressure has a cooling effect, as can be seen by the resulting mist cloud and ice particles; the gas also displaces the oxygen that's necessary to maintain combustion.
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Question 23 Marks
Why is atmosphere essential for life on earth?
Answer
The atmosphere is essential for life because it maintains an appropriate climate for the maintenance of life by carrying out the following activities:
  1. The atmosphere keeps the average temperature of the Earth fairly constant during the day time.
  2. It prevents a sudden increase in temperature during the day time.
  3. It also slows down the escape of heat from the surface of the Earth into outer space during the night time.
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Question 33 Marks
How do plants and animals maintain the balance of oxygen and carbon dioxide in the air?
Answer
  1. Respiration in plants:
    During respiration, plants take in oxygen and release carbon-di-oxide, just as animals also do. Gaseous exchange with air in the atmosphere takes place in plants with stomata.
  2. Photosynthesis:
    During photosynthesis, carbon-di-oxide from the air and water from the soil react in the presence of sunlight to produce food. Plants release oxygen during photosynthesis which is much more than the oxygen consumed by the plants during respiration.
  3. Respiration in animats:
    When we breathe in the air, the oxygen present in the air reacts chemically with digested food within the body to produce carbon-di-oxide gas. The inhaled air contains more oxygen while the exhaled air contains more carbon-di-oxide.
    So plants sent out more oxygen during photosynthesis. Animals sent out more carbon-di-oxide during respiration. Plants take carbon-di-oxide for photosynthesis. Animals take oxygen during respiration. So plants and animals maintain the balance of oxygen and carbon-di-oxide in the air.
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[ 3 Marks Questions ] - Science STD 6 Questions - Vidyadip