Class 7 NCERT Solutions for Social Science (Geography) Chapter – 4 Air

Air

Text Book Page No. 23

Question 1.
For ten days note down weather report from a local newspaper and observe the changes occurring in the weather.

Answer:
Students do themselves.

Exercise Questions and Answers

Question 1.
Answer the following questions.

(1) What is atmosphere ?

Answer:
A huge blanket of air by which our earth is surrounded called atmosphere.

(2) Which two gases make the bulk of atmosphere ?

Answer:
(a) Nitrogen
(b) Oxygen

(3) Which gas creates green house effect in atmosphere ?

Answer:
Carbon dioxide

(4) What is weather ?

Answer:
Weather is hour-to-hour, day to day condition of the atmosphere.

(5) Name three types of rainfall.

Answer:

  1. The convectional rainfall
  2. The orographic rainfall and
  3. The cyclonic rainfall

(6) What is air pressure ?

Answer:
Air pressure is defined as the pressure exerted by the weight of air on the earth’s surface. .

Question 2.
Tick the correct answer

(1) Which of the following gases protects us from, harmful sun rays ?
(a) Carbon dioxide
(b) Nitrogen
(c) Ozone
Answer:
(c) Ozone

(2) The most important layer of atmosphere is
(a) Troposphere
(b) Thermosphere
(c) Mesosphere
Answer:
(a) Troposphere

(3) Which of the following layers of atmosphere is free from clouds ?
(a) Troposphere
(b) Stratosphere
(c) Mesosphere
Answer:
(b) Stratosphere

(4) As we go up the layers of the atmosphere, the pressure
(a) Increases
(b) Decreases
(c) Remain same
Answer:
(b) Decreases

(5) When precipitation comes down to the earth in the liquid form, it is called
(a) Cloud
(b) Rain
(c) Snow
Answer:
(b) Rain

Question 3.
Match the following :

TradeSeasonal wind
winds LooHorizontal movement of air
Monsoon Permanent wind
WindLocal wind

Answer:

TradePermanent wind
winds LooLocal wind
MonsoonSeasonal wind
WindHorizontal movement of air

Give reasons

Question 4.
(1) Wet clothes take longer time to dry on a humid day ?

Answer:
Because on a humid day, there is more water in air than a sunny day. So, air can soak less water from wet clothes, i.e. rate of evaporation decreases.

(2) Amount of insolation decreases from equator towards poles ?

Answer:
Because sun rays fall vertical on the equator while slanting on the poles.

For Fun

Question 5.
(1) Solve this crossword puzzle with the help of given clues (on page 28) :

Answer:

NCERT Solutions for Class 8 Social Science geography 4 img 1

(2) Make a weather calendar for one week. Use pictures or symbols to show different types of weather. You can use more than one symbol in a day, if the weather changes. For example, the sun comes out when rain stops. An example is given below:

Answer:

NCERT Solutions for Class 8 Social Science geography 4 img 2

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