Class 7 Social Studies Chapter AIR Solutions

A. Darken the correct option in OMR Sheet:

1. The summer monsoons blow from ______ while winter monsoons blow from ______.

Options:

(a) Sea to land, land to sea 

(b) Land to sea, sea to land

(c) Sea to land, sea to land

(d) None of these

Answer: (a) Sea to land, land to sea

2. The westerlies blow from ______ in the southern hemisphere.

Options:

(a) South-east 

(b) North-east

(c) North-west

(d) None of these

Answer: (a) South-east

3. Monsoons are ______.

Options:

(a) Permanent

(b) Period winds 

(c) Sea breeze

(d) None of these

Answer: (b) Period winds

4. Equatorial low pressure belt is called ______.

Options:

(a) Doldrums

(b) Cold pressure belts

(c) Shelter

(d) None of these

Answer: (a) Doldrums

B. Fill in the blanks:

1. ______ is a process by which water changes into vapour.

Answer: Evaporation

2. Air pressure ______ with altitude.

Answer: Decreases

3. The earth's surface is heated by ______.

Answer: Solar radiation

4. Atmospheric pressure is measured by an instrument called ______.

Answer: Barometer

C. Match the following:

Column A                          Column B

1. Raingauge                   (e) Rainfall

2. Barometer                    (d) Air pressure

3. Wind Vane                 (c) Wind direction

4. Thermometer             (b) Temperature

5. Anemometer               (a) Wind speed

Answer: 1 → (e) Rainfall

2 → (d) Air pressure

3 → (c) Wind direction

4 → (b) Temperature

5 → (a) Wind speed

D. Write 'T' for True and 'F' for False:

1. When we go to high mountains, our ears pop up.

Answer: True (T)

2. Evaporation takes place more quickly in the higher latitudes.

Answer: False (F)

3. Ozone is the most important protective layer of atmosphere.

Answer: True (T)

4. The air is composed of a single gas.

Answer: False (F)

E. Answer the following questions in short:

1. What is atmosphere?

Answer:

The atmosphere is the blanket of air that surrounds the Earth. It contains different gases and protects all living beings.

2. Write the amount of oxygen in the atmosphere.

Answer:

Oxygen makes up about 21% of the atmosphere.

3. Name the layers of air.

Answer:

•Troposphere

•Stratosphere

•Mesosphere

•Thermosphere

•Exosphere

4. What is evaporation?

Answer:

Evaporation is the process by which water changes into water vapour due to the heat of the Sun.

F. Answer the following questions in detail:

1. Describe the structure of atmosphere.

Answer:

The atmosphere is divided into five layers:

•Troposphere – The lowest layer where weather changes occur.

•Stratosphere – It contains the ozone layer that protects us from harmful ultraviolet rays.

•Mesosphere – Meteors burn up in this layer.

•Thermosphere – This layer is very hot and helps in radio communication.

•Exosphere – It is the outermost 

layer and merges into outer space.

2. What are the major gases of the atmosphere?

Answer:

The atmosphere mainly consists of:

•Nitrogen – 78%

•Oxygen – 21%

•Argon – 0.93%

•Carbon dioxide – 0.04%

It also contains water vapour, dust particles and small amounts of gases like helium and methane.

3. What is atmospheric pressure?

Answer:

Atmospheric pressure is the force exerted by the weight of air on the Earth's surface. It decreases with increasing altitude and is measured using a barometer.

4. Briefly describe the factors affecting the temperature of the atmosphere.

Answer:

The temperature of a place depends on several factors:

•Latitude

•Altitude

•Distance from the sea

•Winds

•Ocean currents

•Direction of mountain ranges

These factors influence the climate and temperature of different places.