Air and Atmosphere
The Atmosphere: The layer of air that surrounds the Earth is called the Atmosphere.
The atmosphere has five layers.
- Troposphere: This layer is closest to the surface of the Earth. The troposphere starts at the Earth's surface and extends 8 to 14.5 kilometers high (5 to 9 miles). This part of the atmosphere is the densest. Almost all weather is in this region.
- Stratosphere: This is the layer next to the troposphere. Aircrafts usually fly in this layer. The ozone layer is present within this layer.
- Mesosphere: It is the layer above the stratosphere and extends to 85 kilometers. Fragments of rock and dust (meteors) that enter the Earth's atmosphere burn up in this layer.
- Thermosphere: The thermosphere starts just above the mesosphere and extends to 600 kilometers high. Artifical satellites orbit the Earth in this layer.
- Exosphere: It is the outermost layer of the atmosphere. extends up to 10,000 km.
Why air is a mixture and not a pure substance?
Reasons:
- The composition of air varies from place to place.
- The different constituents of the air retain their original properties.
- There is no specific chemical formula for air.
- The components of air can be separated by simple physical methods.
Constituents of Air:
Constituents of Air
Percentage by Volume
Properties and Uses
Nitrogen
78%
-
Nitrogen is an inert gas
-
It does not support burning
-
It is an important component of proteins in living things.
Oxygen
21%
-
Oxygen is chemically reactive gas
-
It supports burning
-
It is essential for respiration in living organisms.
Carbon Dioxide
0.04%
-
Carbon dioxide is a chemically reactive gas.
-
It does not support burning.
-
It is necessary for photosynthesis in plants.
Noble Gases such as argon, helium, neon, krypton and xenon
0.93%
-
These gases are inert means non-reactive.
-
Helium, neon and argon are used to light signboards.
-
Helium is used in weather balloons
-
Krypton is used photography.
-
Xenon is used in the manufacturing of semiconductors.
Water vapour
Variable
-
Water vapour present in the air is also called humidity.
-
It is responsible for weather changes such as rain.
Impurities: Dust particles, carbon dioxide, sulfur dioxide, oxides of nitrogen
Variable
-
Impurities present in the air may lead to acid rain.
-
These may also cause respiratory problems, skin diseases and cancer.
- The composition of air varies from place to place.
- The different constituents of the air retain their original properties.
- There is no specific chemical formula for air.
- The components of air can be separated by simple physical methods.
Constituents of Air:
Constituents of Air
|
Percentage by Volume
|
Properties and Uses
|
Nitrogen
|
78%
|
|
Oxygen
|
21%
|
|
Carbon Dioxide
|
0.04%
|
|
Noble Gases such as argon, helium, neon, krypton and xenon
|
0.93%
|
|
Water vapour
|
Variable
|
|
Impurities: Dust particles, carbon dioxide, sulfur dioxide, oxides of nitrogen
|
Variable
|
|
Importance of Air:
- Respiration: All living things breath in the air.
- Inhaled air: The air we breathe in is called inhaled air. The oxygen in the inhaled air is used to break down food and release energy.
- Respiration: The process of breaking down food to release carbon dioxide, water and energy is called respiration.
- Exhaled air: The air we breathe out is called exhaled air. Exhaled air has more carbon dioxide than inhaled air.
- The process of respiration continuously releases carbon dioxide into the atmosphere. It can be summarized as
- Food + Oxygen ------> Energy + Water vapour + Carbon Dioxide
- Photosynthesis :
- Green plants manufacture food through the process of photosynthesis.
- In this process, food is synthesized in the form of glucose in the presence of sunlight, water, and carbon dioxide.
- Green plants have a pigment called chlorophyll which helps to carry out photosynthesis.
- Water is broken down into hydrogen and oxygen with the help of sunlight. Carbon dioxide combines with hydrogen a nd oxygen to form glucose. This glucose is stored in the form of starch
- sunlight
- Carbon dioxide + Water ---------> Glucose + Oxygen
- chlorophyll
Respiration
Photosynthesis
The process of breaking down food to release carbon dioxide, water and energy is called respiration.
In this process, food is synthesized in the form of glucose in the presence of sunlight, water and carbon dioxide.
The oxygen in the inhaled air is used to break down food and release energy.
Green plants have a pigment called chlorophyll which helps to carry out photosynthesis.
In this process, carbon dioxide is released.
In this process, Oxygen is released.
Food + Oxygen ------> Energy + Water vapour + Carbon Dioxide
sunlight
Why plants and animals are interdependent?
How photosynthesis and respiration are interrelated?
Ans: Plants and animals are interdependent because the carbon dioxide required by plants for the process of photosynthesis is released by animals during respiration and the oxygen required by animals for the process of respiration is released by plants during the process of photosynthesis.
Why do we need to plant more trees?
Give reasons: We should grow more trees.
Explain how the balance of oxygen and carbon dioxide is maintained in the air.
Ans:
- The carbon dioxide required by plants for the process of photosynthesis is released by animals during respiration
- The oxygen required by animals for the process of respiration is released by plants during the process of photosynthesis.
- Thus the balance of oxygen and carbon dioxide is maintained in the air.
- But, due to a continuous increase in deforestation (cutting down trees) and atmospheric pollution, the balance of oxygen and carbon dioxide gets disturbed.
- Therefore we need to plant and grow more trees to resume the balance of oxygen-carbon dioxide in the air.
Burning = Combustion
A chemical change (process) in which a substance combines with oxygen and releases energy in the form of heat and light is called burning or combustion.
Substances like wood, coal, paper and candles burn in the presence of air and release energy. Any substance that burns uses oxygen from the air and releases carbon dioxide into the air.
Fuels
A substance that releases heat and light when burnt in the air is called fuel. During burning, fuels use oxygen and release carbon dioxide into the atmosphere.
Fuel + Oxygen ------> Heat + Light +Carbon Dioxide +Water vapour
Based on their physic state fuels are classified into following three types:
- Solid Fuels: Wood and coal are solid fuels.
- Liquid fuels: Kerosene, petrol and diesel are liquid fuels. They are obtained by the fractional distillation of petroleum.
- Gaseous fuels: Liquefied petroleum gas (LPG) and compressed natural gas (CNG) are gaseous fuels. They are also obtained by fractional distillation of petroleum
Uses of Fuels
- Fuels are used for cooking food because when combined with oxygen, fuels release energy in the form of heat which can be used for cooking. LPG and kerosene are used for cooking food.
- Petrol and diesel are used in automobiles and machines.
- Kerosene is used in cooking stove and for lighting lamps.
- CNG is preferred fuel for running automobiles because it is cheaper and less pollution than other fuels.
Burning
Respiration
A chemical change (process) in which a substance combines with oxygen and releases energy in the form of heat and light is called burning.
The process of breaking down food to release carbon dioxide, water and energy, by living things, is called respiration.
The energy released in the process of burning is used in automobiles, machines and cooking food,
The energy released in the process of respiration is used by living things to grow.
A substance + oxygen ----à Heat + Light + Carbon dioxide
Food + Oxygen ------> Energy + Water vapour + Carbon Dioxide
Why is nitrogen considered so important for organisms?
Ans: Nitrogen is the major component of air (78%) and is an essential nutrient for all organisms because
- It forms the building blocks of proteins, enzymes and other cellular constituents which are essential for all forms of life.Proteins make up our skin, hair and help in carrying out various processes in the body like digestion of food, growth, and repair.
- Plants need nitrogen for growth and it forms an important constituent of chlorophyll.
What is Nitrogen fixation? How do organisms obtain Nitrogen?
Ans: The process by which free nitrogen in the air is converted to soluble nitrate with the help of blue-green algae and certain types of bacteria living in the soil is called nitrogen fixation.
Most of the organisms cannot use the nitrogen directly from the atmosphere. It becomes available to organisms when it is converted into soluble nitrogen compounds (nitrates or fixed nitrogen). the soluble nitrogen compounds are absorbed easily by plants from the soil. Other organisms get nitrogen when they consume the plants.
Explain the term air pollution. List three air pollutants.
Ans:
Air Pollution
The release of harmful substances such as hydrogen sulphide, sulphur dioxide and carbon monoxide into the air is called air pollution
Air pollutants:
- hydrogen sulphide
- sulphur dioxide
- carbon monoxide
Common sources of air pollution
- Automobile exhaust
- Thermal power plants that burn coal to produce electricity
- Factories that burn fuels and release polluting gases.
Air pollution can be controlled by
- growing more trees
- setting up factories in non-residential areas
- using eco-friendly, non-polluting products
- controlling deforestation
- using chimneys and filters in industrial complexes to absorb pollutants
Global Warming :
The increase in the temperature of the Earth's atmosphere due to the increase in the concentration of gases such as carbon dioxide is called global warming.
What causes global warming?
Ans: Activities like deforestation and the burning of fossil fuels increase the concentration of carbon dioxide, methane, nitrous oxide, water vapour and other gases in the atmosphere. These gases prevent solar radiation reflected from the Earth's surface from returning to space. Due to this, the temperature f the Earth increases and leads to global warming.
- Respiration: All living things breath in the air.
- Inhaled air: The air we breathe in is called inhaled air. The oxygen in the inhaled air is used to break down food and release energy.
- Respiration: The process of breaking down food to release carbon dioxide, water and energy is called respiration.
- Exhaled air: The air we breathe out is called exhaled air. Exhaled air has more carbon dioxide than inhaled air.
- The process of respiration continuously releases carbon dioxide into the atmosphere. It can be summarized as
- Food + Oxygen ------> Energy + Water vapour + Carbon Dioxide
- Photosynthesis :
- Green plants manufacture food through the process of photosynthesis.
- In this process, food is synthesized in the form of glucose in the presence of sunlight, water, and carbon dioxide.
- Green plants have a pigment called chlorophyll which helps to carry out photosynthesis.
- Water is broken down into hydrogen and oxygen with the help of sunlight. Carbon dioxide combines with hydrogen a nd oxygen to form glucose. This glucose is stored in the form of starch
- sunlight
- Carbon dioxide + Water ---------> Glucose + Oxygen
- chlorophyll
Respiration
|
Photosynthesis
|
The process of breaking down food to release carbon dioxide, water and energy is called respiration.
|
In this process, food is synthesized in the form of glucose in the presence of sunlight, water and carbon dioxide.
|
The oxygen in the inhaled air is used to break down food and release energy.
|
Green plants have a pigment called chlorophyll which helps to carry out photosynthesis.
Water is broken down into hydrogen and oxygen with the help of sunlight. Carbon dioxide combines with hydrogen and oxygen to form glucose. This glucose is stored in the form of starch
|
In this process, carbon dioxide is released.
|
In this process, Oxygen is released.
|
Food + Oxygen ------> Energy + Water vapour + Carbon Dioxide
|
sunlight
Carbon dioxide + Water ----------------> Glucose + Oxygen
chlorophyll
|
Why plants and animals are interdependent?
How photosynthesis and respiration are interrelated?
Ans: Plants and animals are interdependent because the carbon dioxide required by plants for the process of photosynthesis is released by animals during respiration and the oxygen required by animals for the process of respiration is released by plants during the process of photosynthesis.
Why do we need to plant more trees?
Give reasons: We should grow more trees.
Explain how the balance of oxygen and carbon dioxide is maintained in the air.
Ans:
- The carbon dioxide required by plants for the process of photosynthesis is released by animals during respiration
- The oxygen required by animals for the process of respiration is released by plants during the process of photosynthesis.
- Thus the balance of oxygen and carbon dioxide is maintained in the air.
- But, due to a continuous increase in deforestation (cutting down trees) and atmospheric pollution, the balance of oxygen and carbon dioxide gets disturbed.
- Therefore we need to plant and grow more trees to resume the balance of oxygen-carbon dioxide in the air.
Burning = Combustion
A chemical change (process) in which a substance combines with oxygen and releases energy in the form of heat and light is called burning or combustion.
Substances like wood, coal, paper and candles burn in the presence of air and release energy. Any substance that burns uses oxygen from the air and releases carbon dioxide into the air.
Fuels
A substance that releases heat and light when burnt in the air is called fuel. During burning, fuels use oxygen and release carbon dioxide into the atmosphere.
Fuel + Oxygen ------> Heat + Light +Carbon Dioxide +Water vapour
Based on their physic state fuels are classified into following three types:
- Solid Fuels: Wood and coal are solid fuels.
- Liquid fuels: Kerosene, petrol and diesel are liquid fuels. They are obtained by the fractional distillation of petroleum.
- Gaseous fuels: Liquefied petroleum gas (LPG) and compressed natural gas (CNG) are gaseous fuels. They are also obtained by fractional distillation of petroleum
Uses of Fuels
- Fuels are used for cooking food because when combined with oxygen, fuels release energy in the form of heat which can be used for cooking. LPG and kerosene are used for cooking food.
- Petrol and diesel are used in automobiles and machines.
- Kerosene is used in cooking stove and for lighting lamps.
- CNG is preferred fuel for running automobiles because it is cheaper and less pollution than other fuels.
Burning
|
Respiration
|
A chemical change (process) in which a substance combines with oxygen and releases energy in the form of heat and light is called burning.
|
The process of breaking down food to release carbon dioxide, water and energy, by living things, is called respiration.
|
The energy released in the process of burning is used in automobiles, machines and cooking food,
|
The energy released in the process of respiration is used by living things to grow.
|
A substance + oxygen ----à Heat + Light + Carbon dioxide
|
Food + Oxygen ------> Energy + Water vapour + Carbon Dioxide
|
Why is nitrogen considered so important for organisms?
Ans: Nitrogen is the major component of air (78%) and is an essential nutrient for all organisms because
- It forms the building blocks of proteins, enzymes and other cellular constituents which are essential for all forms of life.Proteins make up our skin, hair and help in carrying out various processes in the body like digestion of food, growth, and repair.
- Plants need nitrogen for growth and it forms an important constituent of chlorophyll.
What is Nitrogen fixation? How do organisms obtain Nitrogen?
Ans: The process by which free nitrogen in the air is converted to soluble nitrate with the help of blue-green algae and certain types of bacteria living in the soil is called nitrogen fixation.
Most of the organisms cannot use the nitrogen directly from the atmosphere. It becomes available to organisms when it is converted into soluble nitrogen compounds (nitrates or fixed nitrogen). the soluble nitrogen compounds are absorbed easily by plants from the soil. Other organisms get nitrogen when they consume the plants.
Explain the term air pollution. List three air pollutants.
Ans:
Air Pollution
The release of harmful substances such as hydrogen sulphide, sulphur dioxide and carbon monoxide into the air is called air pollution
Air pollutants:
- hydrogen sulphide
- sulphur dioxide
- carbon monoxide
Common sources of air pollution
- Automobile exhaust
- Thermal power plants that burn coal to produce electricity
- Factories that burn fuels and release polluting gases.
Air pollution can be controlled by
- growing more trees
- setting up factories in non-residential areas
- using eco-friendly, non-polluting products
- controlling deforestation
- using chimneys and filters in industrial complexes to absorb pollutants
Global Warming :
The increase in the temperature of the Earth's atmosphere due to the increase in the concentration of gases such as carbon dioxide is called global warming.
What causes global warming?
Ans: Activities like deforestation and the burning of fossil fuels increase the concentration of carbon dioxide, methane, nitrous oxide, water vapour and other gases in the atmosphere. These gases prevent solar radiation reflected from the Earth's surface from returning to space. Due to this, the temperature f the Earth increases and leads to global warming.
What causes global warming?
Ans: Activities like deforestation and the burning of fossil fuels increase the concentration of carbon dioxide, methane, nitrous oxide, water vapour and other gases in the atmosphere. These gases prevent solar radiation reflected from the Earth's surface from returning to space. Due to this, the temperature f the Earth increases and leads to global warming.
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