JAC Class 7 Social Science Solutions Geography Chapter 4 Air

JAC Board Class 7th Social Science Solutions Geography Chapter 4 Air

JAC Class 7th Geography Air InText Questions and Answers

Page 21

Question 1.
Is global warming a serious issue in today’s world?
Answer:
Concern about climate change is much less pervasive in the United States, China and Russia than among other leading nations. Just 44% in the U.S. and Russia, and even fewer in China (30%), consider global warming to be a very serious problem.

Page 23

Question 2.
For ten days note down weather report from a local newspaper and observe the changes occurring in the weather.
Answer:
Students need to do it by their own.

JAC Class 7 Social Science Solutions Geography Chapter 4 Air

JAC Class 7th Geography Air Textbook Questions and Answers

Question 1.
Answer the following questions.
(i) What is atmosphere?
Answer:
Atmosphere is a huge layer of air that surrounds the earth. It shields and guard us from the harmful rays of the sun. rays of the sun. rays of the sun.

(ii) Which two gases make the bulk of the atmosphere?
Answer:
The two gases which make the bulk of the atmosphere are nitrogen (78% ) and oxygen (21%).

(iii)
Which gas creates greenhouse effect in the atmosphere?
Answer:
The gas which creates greenhouse effect in the atmosphere is carbon dioxide.

(iv) What is weather?
Answer:
An hour to hour, day to day condition of the atmosphere is called as the weather. It is the total atmospheric conditions of a particular place at a particular time regarding temperature, air pressure, clouds, wind, humidity, etc.

(v) Name three types of rainfall?
Answer:
Three types of rainfall are:

  • Convectional rainfall
  • Orographic rainfall
  • Cyclonic rainfall

(vi) What is air pressure?
Answer:
Air pressure is the pressure which is exerted by the weight of air on the earth’s surface.

Tick (√) the correct answer.

Question 2.
(i) Which of the following gases protects us from harmful sun rays?
(a) Carbon dioxide
(b) Nitrogen
(c) Ozone
Answer:
(c) Ozone

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

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

JAC Class 7 Social Science Solutions Geography Chapter 4 Air

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

(v) 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.

(i) Trade winds (a) Incoming solar energy
(ii) Loo (b) Seasonal wind
(iii) Monsoon (c) Horizontal movement of Air
(iv)Wind (d) Layer of ozone gas
(e) Permanent wind
(f) Local wind

Answer:

(i) Trade winds (e) Permanent wind
(ii) Loo (f) Local wind
(iii) Monsoon (b) Seasonal wind
(iv) Wind (c) Horizontal movement of air

 

Question 4.
Give reasons.

  1. Wet clothes take longer time to dry on a humid day?
  2. Amount of insolation decreases from equator towards poles?

Answer:
1. The air is full of water vapour on a humid day. So, the evaporation is very slow due to low temperature. That’s why, wet clothes take longer time to dry on a humid day.

2. On equator, insolation comes through on vertical rays. So, it covers up less amount of space but more heat is felt when it goes up from equator towards poles and the sun rays become slanting. Though slanting rays heat up more amount of space, the level of hotness is felt less. That’s why, amount of insolation decrease from equator towards poles.

Question 5.
(For Fun)

(i) Solve this crossword puzzle with the help of given clues:
JAC Class 7 Social Science Solutions Geography Chapter 4 Air 1

Across:
6. An Indian tree having extraordinary quality of providing oxygen round the clock
8. Gas present in atmosphere occupying only 0.03% by volume
11. Outermost layer of atmosphere
12. Mixture of many gases
14. Life giving gas
15. Air in motion
16. An indian tree valued highly for medicinal properties
18. Gas protecting us from harmful sun rays
19. Low pressure area

Down
1. Amount of water vapour in air
2. Condensation of water vapours around dust particles in atmosphere
3. Example of local wind blowing in summer in northern india
4. Short term changes in atmosphere
5. Precipitation in liquid form
7. Blanket of air around the earth
9. Instrument to measure pressure
10. Incoming solar radiation
13. Reduces visibility in winters
17. It is time when sun is overhead
Answer:

Across:
6. Peepal
11. Exosphere
14. Oxygen
16. Neem
19. Cyclone

Down:
1. Humidity
3. Loo
5. Rain
9. Barometre
10. Insolation
17. Noon
8. Carbon dioxide
12. Air
15. Wind
18. Ozone

(ii) 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:
Hint: Students can do it in this manner.
JAC Class 7 Social Science Solutions Geography Chapter 4 Air 2

JAC Class 7 Social Science Solutions Geography Chapter 4 Air 3

JAC Class 7th Geography Air Important Question and Answers

Multiple Choice Questions

Question 1.
In the atmosphere, the most abundant gas is
(a) Oxygen
(b) Carbon dioxide
(c) Nitrogen
(d) Helium
Answer:
(c) Nitrogen

Question 2.
The winds which below constantly throughout the year in a particular direction is known as
(a) Local winds
(b) Seasonal winds
(c) Permanent winds
(d) None of the these
Answer:
(a) Local winds

JAC Class 7 Social Science Solutions Geography Chapter 4 Air

Question 3.
An hour to hour, day to day condition of the atmosphere is known as
(a) temperature
(b) weather
(c) climate
(d) degree
Answer:
(b) weather

Question 4.
Exosphere is the layer of the atmosphere.
(a) uppermost
(b) middle
(c) lower most
(d) none of these
Answer:
(a) uppermost

Question 5.
The thermosphere extends between
(a) 90 – 370 km
(b) 100 – 350 km
(c) 50 – 300 km
(d) 80 – 400 km
Answer:
(d) 80 – 400 km

Question 6.
The balance of and gets disturbed, if we cut down trees and forests.
(a) oxygen, helium
(b) nitrogen, heiium
(c) oxygen, carbon dioxide
(d) oxygen, nitrogen
Answer:
(c) oxygen, carbon dioxide

Question 7.
The air which we inhale and exhale means breathe exists in the
(a) mesosphere
(b) stratosphere
(c) troposphere
(d) exosphere
Answer:
(c) troposphere

Question 8.
The instrument which measures the temperature is
(a) Barometer
(b) Thermometer
(c) Wind vane
(d) None of these
Answer:
(b) Thermometer

Question 9.
In the atmosphere, the ozone layer exists in the
(a) Stratosphere
(b) Exosphere
(c) Mesosphere
(d) Troposphere
Answer:
(a) Stratosphere

Question 10.
The other name of greenhouse gas is
(a) oxygen
(b) nitrogen
(c) argon
(d) carbon dioxide
Answer:
(b) nitrogen

Very Short Answer Type Questions

Question 1.
What do you mean by smog?
Answer:
Smog is the combination of smoke and fog. It generally occurs during winter season.

Question 2.
What will happen if there is very less rainfall?
Answer:
Water scarcity and drought occurs if there is very less rainfall.

JAC Class 7 Social Science Solutions Geography Chapter 4 Air

Question 3.
What are the various forms of precipitation?
Answer:
Various forms of precipitation are rain,snow, sleet and hail.

Question 4.
Give a word/term for the hot and dry wind of northern plains of India.
Answer: Loo.

Question 5. Air pressure is highest at which area?
Answer:
Air pressure is highest at the sea level

Question 6.
What are the three types of winds?
Answer:
The three types of winds are:

  • Permanent winds
  • Seasonal winds
  • Local winds.

Question 7.
When air is heated, what occurs?
Answer:
Air expands and becomes lighter and goes up when the air is heated.

Question 8.
Ozone layer is important for us. Why?
Answer:
Ozone layer is important for us because it protects and shields us from harmful reactions and effects of the sun rays.

Question 9.
Green plants use carbon dioxide. Why?
Answer:
Green plants use carbon dioxide because it helps them to prepare their food and release oxygen.

Question 10.
What is the consequence and importance of greenhouse gas?
Answer:
The consequence and importance of greenhouse gas is that the earth would have been too cold to live in.

Short Answer Type Questions

Question 1.
What are the instruments called for the measurement of air pressure and the measurement of amount of rainfall?
Answer:
The instruments are called as barometer for the measurement of air pressure and rain gauge for the measurement of amount of rainfall.

Question 2.
What do you mean by a climate of a place or area?
Answer:
The average weather condition of a place or area for a longer period of time constitutes the climate of a place.

Question 3.
What are permanent winds?
Answer:
Winds which blow constantly throughout the year in a particular direction is called as the permanent winds. The trade wind, westerlies and easterlies are the permanent winds.

Question 4.
What is the role of water vapour?
Answer:
One of the major component of the atmosphere is water vapour and it plays a very important role in climatic changes and results in precipitation.

JAC Class 7 Social Science Solutions Geography Chapter 4 Air

Question 5.
How many types of pollutants are found in the atmosphere?
Answer:
There are mainly two types of pollutants found in the atmosphere

  • Gaseous – carbon dioxide and smog
  • Solid – dust and bacteria

Question 6.
Which ty pe of pressure are exerted by cold and hot air?
Answer:
The air expands when heated up hence becomes lighter and goes up. Cold air is heavy and dense so it tends to go down and sinks. When hot air goes up and rises, from surrounding areas, cold air rushes to fill the gap.

Question 7.
Explain the temperature in cities are much higher than that of the villages.
Answer:
In the cities, we find many high rise buildings. The fnetals and concretes in these buildings and the asaphalt of roads get heated up during the day and this heat is released in the night.The other important cause is that in the cities the crowded buildings trap the warm air and hence raise the temperature of the cities. Therefore, the temperature in cities are much higher than that of the villages.

Question 8.
Poles are covered with snow always. Why?
Answer:
From the equator towards the poles the amount of insolation decreases. Hence, the temperature decreases in the same manner. This is the reason why poles are covered with snow always..

Question 9.
What do you mean by global warming?
Answer:
Global warming happens when the level of carbon dioxide increases in the atmosphere due to factory smoke or car fumes and the heat retained increases the temperature of the earth.

JAC Class 7 Social Science Solutions Geography Chapter 4 Air

Question 10.
Rainfall is important for us when there is excess rain, what happens?
Answer:
For the survival of animals and plants,rainfall is very important. It actually brings fresh water to the surface of the earth. There is water scarcity and drought like situation when there is less rainfall. And, if there is excess rainfall then floods take place which makes the life very difficult to sustain. Many things get damaged such as crops, houses, etc.

Question 11.
In which manner bacteria help plants use nitrogen?
Answer:
For the plant’s survival, nitrogen is very crucial and important. But plants cannot take nitrogen directly from the atmosphere. Hence, bacteria that lives in the soil and roots of some plants take nitrogen from air and changes its form so that the plant can use it.

Long Answer Type Questions

Question 1.
Discuss the different layers of the atmosphere.
Answer:
The atmosphere has five different layers. They are:

  • Troposphere
  • Stratosphere
  • Mesosphere
  • Thermosphere
  • Exosphere
  • Troposphere:
    All the weather characteristics occurs here such as fog, rainfall, hailstorm. This is the thickest and the most important layer of the atmosphere. It has the average height of 13 km. We also find the air which we breathe.
  • Stratosphere:
    It lies just above the troposphere and presents the ideal conditions for flying aeroplanes. Stratosphere extends upto a height of 50 km. It also contains the ozone gas layer which protects us from harmful ultraviolet rays of the sun.
  • Mesosphere:
    It lies above the stratosphere. It extends upto the height of 80 kms. In this layer, meteorites bum up on entering from the space.
  • Thermosphere:
    It lies just above the mesosphere. It extends between 80 400 km. Temperature rises very fast with the increase in height in this layer. In thermosphere, radio waves are transmitted from the earth are reflected back to the earth.
  • Exosphere:
    This is the last and the uppermost layer with very thin air. Light gases such as helium and hydrogen float -into the space from exosphere.

Question 2.
What are the different constituents of air? How they are important to us?
Answer:
The different constituents of air are oxygen, nitrogen, carbon dioxide, ozone, helium, argon and hydrogen. Besides these gases, the air also contains some amount of water vapour and dust particles. They are important to us in many ways:

Oxygen:
It is one of the major gas and second most in volume which makes up about 21% of the air. It is also called as life supporting gas. The atmosphere is continuously recharged and restored of oxygen by green plants through the photosynthesis process and thus keeps a healthy and efficient balance of oxygen in the air. Nitrogen: The total volume of nitrogen is about 78% in the air. The major amount of nitrogen is not utilized in our body system when we inhale. But, plants need nitrogen for the well being and survival.

They absorb it through soil and plant roots. Carbon Dioxide: Carbon dioxide is composed of very small percentage around 0.03% of the air. Then also, it is one of the important gas in maintaining the life cycle of plants on the earth. Carbon dioxide absorbs heat of the sun and warms up the lower atmosphere of the surface of the earth. It is taken by the green plants when human beings and animals release it.

JAC Class 7 Social Science Solutions

JAC Class 7 Social Science Notes Geography Chapter 4 Air

JAC Board Class 7 Social Science Notes Geography Chapter 4 Air

→ Earth is surrounded by a huge layer of air known as atmosphere.

  • On the earth all the living creatures depend on the atmosphere for their survival.
  • With the absence of this layer of protection, we would have been baked by the scorching heat of the sun at daytime and frozen at night time. Hence, the temperature of the earth is liveable due to this layer of air.

JAC Class 7 Social Science Notes Geography Chapter 4 Air

→ Composition of the Atmosphere:

  • The two main gases which make the most of the atmosphere are nitrogen and oxygen. Carbon dioxide, helium, ozone, argon and hydrogen are found in less quantities.
  • Tiny and minute dust particles are also present in the atmosphere apart from these gases.
  • We take some amount of nitrogen when we inhale into our lungs and exhale it.
  • Plants take nitrogen from soil and roots of the plant which is brought by the bacterias and change its form so that plants can use it as they cannot take nitrogen directly.
  • The second most abundant gas found is the oxygen. Green plants produces oxygen during photosynthesis and humans and animals use oxygen to breathe.
  • The balance gets disturbed if we cut down the forests in large numbers.
  • The other important gas is carbon dioxide. Plants use carbon dioxide to make their food and release oxygen. Humans and animals release carbon dioxide.
  • The balance gets disturbed by burning of fuels like oils, coal. Hence, the earth’s climate and weather gets affected by the increased volume of carbon dioxide.

→ Structure of the Atmosphere:

  • Starting from the earth’s surface, the atmosphere has been divided into five layers – Troposphere, Stratosphere, Mesosphere, Thermosphere and Exosphere.
  • Troposphere – Themost important layer of the atmosphere is Troposphere and its average height is 13 km. The air we breathe exists here. Most of the weather incidences such as rainfall, fog and hailstorm occur in this layer.
  • Stratosphere – Stratosphere lies above the troposphere and it extends up to a height of 50 km. This layer is almost free from clouds and related weather incidences are making ideal conditions for flying aeroplanes. One of the important features is that it contains a layer of ozone gas.
  • Mesosphere – The third layer of the atmosphere is mesosphere. Above the stratosphere it is situated and extends up to the height of 80 km. On entering from the space, meteorites bum up in this layer.
  • Thermosphere – Temperature rises very rapidly and fast with increasing height in thermosphere.
  • Ionosphere is a part of this layer and it extends between 80^100 km. Radio transmission happens in this layer. In fact, radio waves transmitted from the earth are reflected back to the earth by this layer.
  • Exosphere- It is the upper most layer of the atmosphere. It has very thin air. Light gases are present such as helium and hydrogen float into the space from here.

→ Weather and Climate:
Weather is the hour-to-hour, day to day condition of the atmosphere. But, the average weather condition or phenomena of a place for a longer period of time is called as the climate of a place.

→ Temperature:

  • The degree or level of hotness and coldness of the air is called as the temperature.
  • The atmosphere’s temperature changes not only between day and night but also from season to season as well.
  • The incoming solar energy intercepted by the earth is called the insolation. It is one of the important factors that influence the distribution of temperature.
  • Towards the poles, the amount of insolation decreases from the equator hence the temperature also decreases.
  • Temperature in cities is much higher than that of villages because of the concrete and metals in buildings and the asphalt of roads get heated up during the day and this is released during the night.

JAC Class 7 Social Science Notes Geography Chapter 4 Air

→ Air Pressure

  • From all directions, the air presses us and our body exerts a counter pressure.
  • The pressure exerted by the weight of air on the earth’s surface is called the air pressure. It is highest at sea level and decreases with height.
  • Low pressure is related to cloudy skies and wet weather. A low-pressure is created in areas where temperature is high and the air gets heated and rises.
  • High pressure is related to clear and sunny skies. Heavy air sinks and creates a high pressure area and the air always moves from high pressure areas to low pressure areas.

→ Wind

  • Wind is the movement of air from high pressure area to low pressure areas.
  • It is divided into three parts:
    • Permanent winds
    • Seasonal winds
    • Local winds
  • Permanent winds are the trade winds, westerlies and easterlies. They blow constantly throughout the year in a particular direction.
  • Seasonal winds are the winds which change their direction in different seasons such as monsoons in India.
  • Local winds are the winds which blow only during a particular period of the day or year in a small area such as land and sea breeze. The hot and dry local wind of northern planes of India is called loo.

→ Moisture

  • We know that when water evaporates from land and different water bodies, it becomes water vapour. Humidity is the moisture in the air at any time. When the air is full of water vapour then it is called as a humid day.
  • Clouds are just masses of water droplets. The water vapour condenses which cause the formation of these droplets of water.
  • Precipitation happens when these droplets of water become too heavy to float in air and then they come down.
  • Rain is the precipitation that comes down to the earth in liquid form.
  • The three types of rainfall are the convectional rainfall, the orographic rainfall and the cyclonic rainfall.
  • For the survival of plants and animals, rainfall is very important as it brings fresh water to the earth’s surface. If rainfall is less then water scarcity and drought occur and if it is more, then floods take place.

JAC Class 7 Social Science Notes