Question Answers chapter Air

1. Answer the following questions.
(i) What is atmosphere?
 Answer: The thick blanket of air (mixture of gases) around the earth is called atmosphere.
(ii) Which two gases make the bulk of the atmosphere?
Answer: Nitrogen and Oxygen
(iii) Which gas creates green house effect in the atmosphere?
Answer: Carbon Dioxide.
(iv) What is weather?
Answer: The state or condition of atmosphere at a particular time and place is called weather.
(v) Name three types of rainfall?
Answer: Orographic, convectional and cyclonic rain.
 (vi) What is air pressure?
Answer: The pressure exerted due to the weight of air on the earth's surface is called air pressure.
Give reasons.
 (i) Wet clothes take longer time to dry on a humid day?
Answer: On a humid day air is saturated with water vapours, therefore wet clothes take longer time to dry.
(ii) Amount of insolation decreases from equator towards poles?
Answer: Since sun rays fall vertically on the equator while on poles rays fall slanting, thus amount of insolation decreases from equator towards poles.
Additional Questions.
(i)                  List three importance of atmosphere.

Answer: Importance of atmosphere

1. The atmosphere prevents the Earth from becoming too hot during the day or too cold during the night.
2. It prevents the harmful ultra-violet rays of the Sun from reaching the Earth’s surface.
3. The atmosphere is the source of life-supporting gases such as Oxygen, Nitrogen, and Carbon dioxide.
(ii)               Write a note on Winds?
Answer: Winds can be broadly divided into three types.
  1. Permanent winds – The trade winds, westerlies and easterlies are the permanent winds. These blow constantly throughout the year in a particular direction. 
  2. Seasonal winds – These winds change their direction in different seasons. For example monsoons in India. 
  3.  Local winds – These blow only during a particular period of the day or year in a small area. For example, land and sea breeze.
  4. What is Global Warming?
Answer: When the greenhouse gases level in the atmosphere increases due to factory smoke or car fumes, the heat retained increases the temperature of the earth. This is called global warming. This rise in temperature causes the snow in coldest parts of the world to melt.

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