Selina Textbook Solutions: Air and Atmosphere | Chemistry Class 6 ICSE PDF Download

 Page 1


POINTS TO REMEMBER 
1. Air cannot be seen as it is transparent we only feel its presence when it blows. 
2. The thick layer of air around earth upto 320 km above the surface is called 
atmosphere. 
3. Air is a mixture of various gases, water vapours, which protects us from harmful 
rays of Sun. It consists of nearly 80% nitrogen, 20% oxygen. 
4. The components of air can be separated by simple physical means. Has no 
formula. 
5. N 2 is inert gas, reduces the effect of O 2 present in air, N 2 is helpful in plant growth 
as it provides nitrates used by plant for formation of protein which is important 
nutrient for animals. 
6. Oxygen is supporter of combustion no burning is possible without O 2 and no life is 
possible without it. 
7. CO 2 is must for plant life, plants prepare their food taking CO 2 from 
air. CO 2 maintains temp, of earth and without CO 2 our planet would be too cold. 
8. Ozone in the upper layers of atmosphere protects the earth from harmful 
ultraviolet rays of Sun. 
9. Air is useful in many ways : Acts as medium for propagation of sound, birds, 
insects to fly in air, air ships, aeroplanes to fly only must due to presence of air. Air 
helps in movement of yachts, parachutes, aircrafts etc. Air is must for animals and 
plants on earth and air dissolved in water for aquatic life. 
10. Respiration : Is a slow chemical process when O 2 present in the inhaled air 
reacts with the digested food material in the body to release energy, CO 2 and 
water. Sugar + Oxygen -> Carbon dioxide + Water + Energy. 
Breathing : The complete process in which air is inhaled and exhaled is called 
breathing. 
11. Combustion : Burning of substance in air completely producing CO 2, heat and 
light. 
12. Photosynthesis : Preparation of food by green plants taking CO 2 from air, water 
from soil in presence of sun light. 
13. Oxygen in air remains constant it is not depleted as plants during day time 
produce lot of O 2 in air. 
14. Soil contains air trapped in between its particle and organisms living there breath 
this oxygen. Due to this earth worms come out of soil during heavy rains as water 
gets into the pores in the soil. 
15. Common pollutant of air are smoke, dust, coal, emitted by industries and 
automobiles. 
16. Gases like SO 2, NO 2 also pollute air as they form corresponding acids when they 
come in contact with water vapours in air and fall down in the form of acid rain with 
rain water. 
17. These pollutants reduce the visibility which lead to accidents, cause global 
warming. 
EXERCISE-I 
Page 2


POINTS TO REMEMBER 
1. Air cannot be seen as it is transparent we only feel its presence when it blows. 
2. The thick layer of air around earth upto 320 km above the surface is called 
atmosphere. 
3. Air is a mixture of various gases, water vapours, which protects us from harmful 
rays of Sun. It consists of nearly 80% nitrogen, 20% oxygen. 
4. The components of air can be separated by simple physical means. Has no 
formula. 
5. N 2 is inert gas, reduces the effect of O 2 present in air, N 2 is helpful in plant growth 
as it provides nitrates used by plant for formation of protein which is important 
nutrient for animals. 
6. Oxygen is supporter of combustion no burning is possible without O 2 and no life is 
possible without it. 
7. CO 2 is must for plant life, plants prepare their food taking CO 2 from 
air. CO 2 maintains temp, of earth and without CO 2 our planet would be too cold. 
8. Ozone in the upper layers of atmosphere protects the earth from harmful 
ultraviolet rays of Sun. 
9. Air is useful in many ways : Acts as medium for propagation of sound, birds, 
insects to fly in air, air ships, aeroplanes to fly only must due to presence of air. Air 
helps in movement of yachts, parachutes, aircrafts etc. Air is must for animals and 
plants on earth and air dissolved in water for aquatic life. 
10. Respiration : Is a slow chemical process when O 2 present in the inhaled air 
reacts with the digested food material in the body to release energy, CO 2 and 
water. Sugar + Oxygen -> Carbon dioxide + Water + Energy. 
Breathing : The complete process in which air is inhaled and exhaled is called 
breathing. 
11. Combustion : Burning of substance in air completely producing CO 2, heat and 
light. 
12. Photosynthesis : Preparation of food by green plants taking CO 2 from air, water 
from soil in presence of sun light. 
13. Oxygen in air remains constant it is not depleted as plants during day time 
produce lot of O 2 in air. 
14. Soil contains air trapped in between its particle and organisms living there breath 
this oxygen. Due to this earth worms come out of soil during heavy rains as water 
gets into the pores in the soil. 
15. Common pollutant of air are smoke, dust, coal, emitted by industries and 
automobiles. 
16. Gases like SO 2, NO 2 also pollute air as they form corresponding acids when they 
come in contact with water vapours in air and fall down in the form of acid rain with 
rain water. 
17. These pollutants reduce the visibility which lead to accidents, cause global 
warming. 
EXERCISE-I 
Question 1. 
What is atmosphere ? 
Answer: 
The earth is surrounded by a thick layer of air called the atmosphere that extends upto a 
height of about 320 kilometres above the surface of the earth. 
Question 2. 
Why can’t we see air ? 
Answer: 
We can’t see air because it is colourless, odourless and transparent gaseous matter. 
Question 3. 
What is wind ? 
Answer: 
Fast moving air is called wind. 
Question 4. 
What would have happened if there would have been no atmosphere around the earth ? 
Answer: 
Without atmosphere life would not be possible as atmosphere protects us from harmful 
gases. We could not live without 
air present in atmosphere. In absence of the atmopshere, the earth would get so cold at 
night that we would not be able to survive. No CO 2 and N 2 for plants without 
atmosphere. 
P.Q. When water is heated, we see bubbles rising up. Why ? 
Answer: 
Water has a lot of air dissolved on it. This is what allows breathing to fishes and other 
aquatic beings. The solubility of gases decreases when the temperature is raised, and 
that is why the dissolved air bubbles out from the water. 
Question 5. 
Why is air called a mixture ? Give five facts in support of your answer. 
Answer: 
Air is a mixture because : 
1. Air has no formula, a mixture has no formula whereas compound has a formula. 
2. No energy changes are involved to form air from various gases. 
3. When air is formed out of its constituents no change in mass and no change in 
volume takes place. 
4. Properties of air vary from place to place and time to time. i.e. there is more CO 2 in 
towns as compared to villages where more oxygen prevails as compared to 
towns. 
5. Components of air can be separated by simple physical methods. 
Page 3


POINTS TO REMEMBER 
1. Air cannot be seen as it is transparent we only feel its presence when it blows. 
2. The thick layer of air around earth upto 320 km above the surface is called 
atmosphere. 
3. Air is a mixture of various gases, water vapours, which protects us from harmful 
rays of Sun. It consists of nearly 80% nitrogen, 20% oxygen. 
4. The components of air can be separated by simple physical means. Has no 
formula. 
5. N 2 is inert gas, reduces the effect of O 2 present in air, N 2 is helpful in plant growth 
as it provides nitrates used by plant for formation of protein which is important 
nutrient for animals. 
6. Oxygen is supporter of combustion no burning is possible without O 2 and no life is 
possible without it. 
7. CO 2 is must for plant life, plants prepare their food taking CO 2 from 
air. CO 2 maintains temp, of earth and without CO 2 our planet would be too cold. 
8. Ozone in the upper layers of atmosphere protects the earth from harmful 
ultraviolet rays of Sun. 
9. Air is useful in many ways : Acts as medium for propagation of sound, birds, 
insects to fly in air, air ships, aeroplanes to fly only must due to presence of air. Air 
helps in movement of yachts, parachutes, aircrafts etc. Air is must for animals and 
plants on earth and air dissolved in water for aquatic life. 
10. Respiration : Is a slow chemical process when O 2 present in the inhaled air 
reacts with the digested food material in the body to release energy, CO 2 and 
water. Sugar + Oxygen -> Carbon dioxide + Water + Energy. 
Breathing : The complete process in which air is inhaled and exhaled is called 
breathing. 
11. Combustion : Burning of substance in air completely producing CO 2, heat and 
light. 
12. Photosynthesis : Preparation of food by green plants taking CO 2 from air, water 
from soil in presence of sun light. 
13. Oxygen in air remains constant it is not depleted as plants during day time 
produce lot of O 2 in air. 
14. Soil contains air trapped in between its particle and organisms living there breath 
this oxygen. Due to this earth worms come out of soil during heavy rains as water 
gets into the pores in the soil. 
15. Common pollutant of air are smoke, dust, coal, emitted by industries and 
automobiles. 
16. Gases like SO 2, NO 2 also pollute air as they form corresponding acids when they 
come in contact with water vapours in air and fall down in the form of acid rain with 
rain water. 
17. These pollutants reduce the visibility which lead to accidents, cause global 
warming. 
EXERCISE-I 
Question 1. 
What is atmosphere ? 
Answer: 
The earth is surrounded by a thick layer of air called the atmosphere that extends upto a 
height of about 320 kilometres above the surface of the earth. 
Question 2. 
Why can’t we see air ? 
Answer: 
We can’t see air because it is colourless, odourless and transparent gaseous matter. 
Question 3. 
What is wind ? 
Answer: 
Fast moving air is called wind. 
Question 4. 
What would have happened if there would have been no atmosphere around the earth ? 
Answer: 
Without atmosphere life would not be possible as atmosphere protects us from harmful 
gases. We could not live without 
air present in atmosphere. In absence of the atmopshere, the earth would get so cold at 
night that we would not be able to survive. No CO 2 and N 2 for plants without 
atmosphere. 
P.Q. When water is heated, we see bubbles rising up. Why ? 
Answer: 
Water has a lot of air dissolved on it. This is what allows breathing to fishes and other 
aquatic beings. The solubility of gases decreases when the temperature is raised, and 
that is why the dissolved air bubbles out from the water. 
Question 5. 
Why is air called a mixture ? Give five facts in support of your answer. 
Answer: 
Air is a mixture because : 
1. Air has no formula, a mixture has no formula whereas compound has a formula. 
2. No energy changes are involved to form air from various gases. 
3. When air is formed out of its constituents no change in mass and no change in 
volume takes place. 
4. Properties of air vary from place to place and time to time. i.e. there is more CO 2 in 
towns as compared to villages where more oxygen prevails as compared to 
towns. 
5. Components of air can be separated by simple physical methods. 
Question 6. 
What are the main components of air ? Write down the composition of three main gases 
present in air by volume. 
Answer: 
Main components of air are : 
 
 
Question 7. 
What do you observe when 
(a) Ice cold water is filled in a glass tumbler. 
(b) A burning candle is covered with an inverted jar. 
(c) Carbon dioxide gas is passed through lime water. 
(d) A beam of light is allowed to enter in a closed dark room through a small hole. 
Answer: 
(a) We will observe that fine water droplets get deposited on the outer wall of the glass 
tumbler. 
(b) The candle burn more brightly because candle gets oxygen support in burning. 
(c) When CO 2 gas is passed through lime water it forms calcium carbonate which is 
white precipitate (turbidity). This gives the milky white appearance to the solution. 
Page 4


POINTS TO REMEMBER 
1. Air cannot be seen as it is transparent we only feel its presence when it blows. 
2. The thick layer of air around earth upto 320 km above the surface is called 
atmosphere. 
3. Air is a mixture of various gases, water vapours, which protects us from harmful 
rays of Sun. It consists of nearly 80% nitrogen, 20% oxygen. 
4. The components of air can be separated by simple physical means. Has no 
formula. 
5. N 2 is inert gas, reduces the effect of O 2 present in air, N 2 is helpful in plant growth 
as it provides nitrates used by plant for formation of protein which is important 
nutrient for animals. 
6. Oxygen is supporter of combustion no burning is possible without O 2 and no life is 
possible without it. 
7. CO 2 is must for plant life, plants prepare their food taking CO 2 from 
air. CO 2 maintains temp, of earth and without CO 2 our planet would be too cold. 
8. Ozone in the upper layers of atmosphere protects the earth from harmful 
ultraviolet rays of Sun. 
9. Air is useful in many ways : Acts as medium for propagation of sound, birds, 
insects to fly in air, air ships, aeroplanes to fly only must due to presence of air. Air 
helps in movement of yachts, parachutes, aircrafts etc. Air is must for animals and 
plants on earth and air dissolved in water for aquatic life. 
10. Respiration : Is a slow chemical process when O 2 present in the inhaled air 
reacts with the digested food material in the body to release energy, CO 2 and 
water. Sugar + Oxygen -> Carbon dioxide + Water + Energy. 
Breathing : The complete process in which air is inhaled and exhaled is called 
breathing. 
11. Combustion : Burning of substance in air completely producing CO 2, heat and 
light. 
12. Photosynthesis : Preparation of food by green plants taking CO 2 from air, water 
from soil in presence of sun light. 
13. Oxygen in air remains constant it is not depleted as plants during day time 
produce lot of O 2 in air. 
14. Soil contains air trapped in between its particle and organisms living there breath 
this oxygen. Due to this earth worms come out of soil during heavy rains as water 
gets into the pores in the soil. 
15. Common pollutant of air are smoke, dust, coal, emitted by industries and 
automobiles. 
16. Gases like SO 2, NO 2 also pollute air as they form corresponding acids when they 
come in contact with water vapours in air and fall down in the form of acid rain with 
rain water. 
17. These pollutants reduce the visibility which lead to accidents, cause global 
warming. 
EXERCISE-I 
Question 1. 
What is atmosphere ? 
Answer: 
The earth is surrounded by a thick layer of air called the atmosphere that extends upto a 
height of about 320 kilometres above the surface of the earth. 
Question 2. 
Why can’t we see air ? 
Answer: 
We can’t see air because it is colourless, odourless and transparent gaseous matter. 
Question 3. 
What is wind ? 
Answer: 
Fast moving air is called wind. 
Question 4. 
What would have happened if there would have been no atmosphere around the earth ? 
Answer: 
Without atmosphere life would not be possible as atmosphere protects us from harmful 
gases. We could not live without 
air present in atmosphere. In absence of the atmopshere, the earth would get so cold at 
night that we would not be able to survive. No CO 2 and N 2 for plants without 
atmosphere. 
P.Q. When water is heated, we see bubbles rising up. Why ? 
Answer: 
Water has a lot of air dissolved on it. This is what allows breathing to fishes and other 
aquatic beings. The solubility of gases decreases when the temperature is raised, and 
that is why the dissolved air bubbles out from the water. 
Question 5. 
Why is air called a mixture ? Give five facts in support of your answer. 
Answer: 
Air is a mixture because : 
1. Air has no formula, a mixture has no formula whereas compound has a formula. 
2. No energy changes are involved to form air from various gases. 
3. When air is formed out of its constituents no change in mass and no change in 
volume takes place. 
4. Properties of air vary from place to place and time to time. i.e. there is more CO 2 in 
towns as compared to villages where more oxygen prevails as compared to 
towns. 
5. Components of air can be separated by simple physical methods. 
Question 6. 
What are the main components of air ? Write down the composition of three main gases 
present in air by volume. 
Answer: 
Main components of air are : 
 
 
Question 7. 
What do you observe when 
(a) Ice cold water is filled in a glass tumbler. 
(b) A burning candle is covered with an inverted jar. 
(c) Carbon dioxide gas is passed through lime water. 
(d) A beam of light is allowed to enter in a closed dark room through a small hole. 
Answer: 
(a) We will observe that fine water droplets get deposited on the outer wall of the glass 
tumbler. 
(b) The candle burn more brightly because candle gets oxygen support in burning. 
(c) When CO 2 gas is passed through lime water it forms calcium carbonate which is 
white precipitate (turbidity). This gives the milky white appearance to the solution. 
(d) We will observe randomly moving dust particles in the beam of light. This confirms 
the presence of dust particles in the air. 
Question 8. 
Write the chemical name of – 
(a) Lime water 
(b) The white insoluble solid formed on reaction of carbon dioxide with lime water. 
Answer: 
(a) Calcium hydroxide Ca(OH) 2 
(b) Calcium carbonate – CaCO 3 
These droplets were present in air as moisture which got condensed on the cooler walls 
of glass tumbler. This shows the presence of water vapours in air. 
EXERCISE-II 
Question 1. 
Name two important processes supported by oxygen present in air. 
Answer: 
Two processes supported by oxygen present in air are : 
1. Combustion 
2. Respiration 
Question 2. 
Give two uses of the following components present in air: 
(a) oxygen 
(b) nitrogen 
(c) carbon dioxide 
(d) water vapour 
Answer: 
(a) Oxygen: For respiration and breathing no life is possible without oxygen. 
Oxygen is the most vital component which is responsible for two most important 
processes, 
(i) Respiration and 
(ii) Combustion. 
Page 5


POINTS TO REMEMBER 
1. Air cannot be seen as it is transparent we only feel its presence when it blows. 
2. The thick layer of air around earth upto 320 km above the surface is called 
atmosphere. 
3. Air is a mixture of various gases, water vapours, which protects us from harmful 
rays of Sun. It consists of nearly 80% nitrogen, 20% oxygen. 
4. The components of air can be separated by simple physical means. Has no 
formula. 
5. N 2 is inert gas, reduces the effect of O 2 present in air, N 2 is helpful in plant growth 
as it provides nitrates used by plant for formation of protein which is important 
nutrient for animals. 
6. Oxygen is supporter of combustion no burning is possible without O 2 and no life is 
possible without it. 
7. CO 2 is must for plant life, plants prepare their food taking CO 2 from 
air. CO 2 maintains temp, of earth and without CO 2 our planet would be too cold. 
8. Ozone in the upper layers of atmosphere protects the earth from harmful 
ultraviolet rays of Sun. 
9. Air is useful in many ways : Acts as medium for propagation of sound, birds, 
insects to fly in air, air ships, aeroplanes to fly only must due to presence of air. Air 
helps in movement of yachts, parachutes, aircrafts etc. Air is must for animals and 
plants on earth and air dissolved in water for aquatic life. 
10. Respiration : Is a slow chemical process when O 2 present in the inhaled air 
reacts with the digested food material in the body to release energy, CO 2 and 
water. Sugar + Oxygen -> Carbon dioxide + Water + Energy. 
Breathing : The complete process in which air is inhaled and exhaled is called 
breathing. 
11. Combustion : Burning of substance in air completely producing CO 2, heat and 
light. 
12. Photosynthesis : Preparation of food by green plants taking CO 2 from air, water 
from soil in presence of sun light. 
13. Oxygen in air remains constant it is not depleted as plants during day time 
produce lot of O 2 in air. 
14. Soil contains air trapped in between its particle and organisms living there breath 
this oxygen. Due to this earth worms come out of soil during heavy rains as water 
gets into the pores in the soil. 
15. Common pollutant of air are smoke, dust, coal, emitted by industries and 
automobiles. 
16. Gases like SO 2, NO 2 also pollute air as they form corresponding acids when they 
come in contact with water vapours in air and fall down in the form of acid rain with 
rain water. 
17. These pollutants reduce the visibility which lead to accidents, cause global 
warming. 
EXERCISE-I 
Question 1. 
What is atmosphere ? 
Answer: 
The earth is surrounded by a thick layer of air called the atmosphere that extends upto a 
height of about 320 kilometres above the surface of the earth. 
Question 2. 
Why can’t we see air ? 
Answer: 
We can’t see air because it is colourless, odourless and transparent gaseous matter. 
Question 3. 
What is wind ? 
Answer: 
Fast moving air is called wind. 
Question 4. 
What would have happened if there would have been no atmosphere around the earth ? 
Answer: 
Without atmosphere life would not be possible as atmosphere protects us from harmful 
gases. We could not live without 
air present in atmosphere. In absence of the atmopshere, the earth would get so cold at 
night that we would not be able to survive. No CO 2 and N 2 for plants without 
atmosphere. 
P.Q. When water is heated, we see bubbles rising up. Why ? 
Answer: 
Water has a lot of air dissolved on it. This is what allows breathing to fishes and other 
aquatic beings. The solubility of gases decreases when the temperature is raised, and 
that is why the dissolved air bubbles out from the water. 
Question 5. 
Why is air called a mixture ? Give five facts in support of your answer. 
Answer: 
Air is a mixture because : 
1. Air has no formula, a mixture has no formula whereas compound has a formula. 
2. No energy changes are involved to form air from various gases. 
3. When air is formed out of its constituents no change in mass and no change in 
volume takes place. 
4. Properties of air vary from place to place and time to time. i.e. there is more CO 2 in 
towns as compared to villages where more oxygen prevails as compared to 
towns. 
5. Components of air can be separated by simple physical methods. 
Question 6. 
What are the main components of air ? Write down the composition of three main gases 
present in air by volume. 
Answer: 
Main components of air are : 
 
 
Question 7. 
What do you observe when 
(a) Ice cold water is filled in a glass tumbler. 
(b) A burning candle is covered with an inverted jar. 
(c) Carbon dioxide gas is passed through lime water. 
(d) A beam of light is allowed to enter in a closed dark room through a small hole. 
Answer: 
(a) We will observe that fine water droplets get deposited on the outer wall of the glass 
tumbler. 
(b) The candle burn more brightly because candle gets oxygen support in burning. 
(c) When CO 2 gas is passed through lime water it forms calcium carbonate which is 
white precipitate (turbidity). This gives the milky white appearance to the solution. 
(d) We will observe randomly moving dust particles in the beam of light. This confirms 
the presence of dust particles in the air. 
Question 8. 
Write the chemical name of – 
(a) Lime water 
(b) The white insoluble solid formed on reaction of carbon dioxide with lime water. 
Answer: 
(a) Calcium hydroxide Ca(OH) 2 
(b) Calcium carbonate – CaCO 3 
These droplets were present in air as moisture which got condensed on the cooler walls 
of glass tumbler. This shows the presence of water vapours in air. 
EXERCISE-II 
Question 1. 
Name two important processes supported by oxygen present in air. 
Answer: 
Two processes supported by oxygen present in air are : 
1. Combustion 
2. Respiration 
Question 2. 
Give two uses of the following components present in air: 
(a) oxygen 
(b) nitrogen 
(c) carbon dioxide 
(d) water vapour 
Answer: 
(a) Oxygen: For respiration and breathing no life is possible without oxygen. 
Oxygen is the most vital component which is responsible for two most important 
processes, 
(i) Respiration and 
(ii) Combustion. 
(b) Nitrogen : Present in air gets fixed up in the soil as nitrates used by plants for their 
growth and for the formation of protein an important nutrient for animals. It is used to 
make fertilizers and various nitrogenous products. 
(c) Carbon dioxide : Carbon dioxide is used by plants to prepare their food by 
photosynthesis. Dry ice (solid carbon-dioxide) is used as a refrigerant. Carbon dioxide is 
used to prepare fizzy drinks like soda water. 
(d) Water vapour : Water vapors present in air provide moisture for both plants and 
animals. It also helps in predicting climatic conditions of a particular area as its amount 
varies from place to place and time to time. 
Question 3. 
Define the following: 
(a) Respiration 
(b) Photosynthesis 
(c) Combustion. 
Answer: 
(a) Respiration : Respiration is a chemical process that takes place in all living beings 
(slow in plants). In this process, oxygen present in inhaled air reacts with the digested 
food material in the body. This results in release of energy, carbon-dioxide and water. 
Sugar + Oxygen ? CO 2 + Water + Energy. 
(b) Photosynthesis : Process of producing food by green plants taking CO 2 from air, 
water from soil by roots and in presence of sun light and chlorophyll is called 
photosynthesis. 
(c) Combustion : Combustion also called burning “is burning of substance in oxygen of 
air completely producing heat and light is called combustion.” 
Question 4. 
What are fuels ? Give two examples of modern fuels. 
Answer: 
Fuels : The substances which burn in air to produce large amount of energy in the form 
of heat and light are called fuels. 
Examples : 
1. CNG (Compressed natural gas) 
2. LPG (Liquefied natural gas) 
Question 5. 
Give reasons :