Natural Resources: NBSE Class 9 Environment

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Get summaries, questions, answers, solutions, notes, extras, PDF and guide of Chapter 7 Natural Resources, NBSE Class 9 Environmental Education textbook, which is part of the syllabus of students studying under Nagaland Board. These solutions, however, should only be treated as references and can be modified/changed.

Summary

Natural resources are things in nature that help humans live and grow. A resource is not useful by itself. It becomes useful when people use it for a purpose. For example, oil was not a resource until people started using it. Natural resources can be divided into two groups. These are inexhaustible and exhaustible resources. Inexhaustible resources like sunlight and wind do not run out. Exhaustible resources can be renewable or non-renewable. Renewable resources like water and plants can be replaced. Non-renewable resources like coal and oil cannot be replaced once they are used up.

Air is made of gases like nitrogen, oxygen, and carbon dioxide. Oxygen helps living things breathe. Nitrogen makes up most of the air but does not react much. Carbon dioxide helps plants grow and keeps the Earth warm. Air pollution happens because of cars, factories, and farming. Polluted air harms people, animals, and plants. Water covers most of the Earth but only a small part is fresh and usable. Freshwater comes from rain and is stored in rivers, lakes, and underground. People use water to drink, clean, and make electricity. But water is becoming scarce because of pollution and overuse.

Soil supports plants and stores water and nutrients. It is made of broken-down rocks, dead plants, and tiny spaces for air and water. Soil helps plants grow and gives homes to many creatures. But soil is being polluted by chemicals and waste. Cutting down trees causes soil erosion. Eroded soil fills rivers and dams, causing floods.

Forests are large areas covered with trees. They give homes to plants and animals. Forests protect soil, store water, and help control the climate. Trees take in carbon dioxide and give out oxygen. Forests also provide wood, food, and materials for making things. But deforestation is harming forests and the life inside them.

Minerals and metals come from rocks in the Earth. People dig them up through mining. Coal, oil, and natural gas are fuels. Coal is used to make electricity and steel. Oil is turned into fuel for cars and raw material for products like plastic. Natural gas is used for cooking, heating, and making chemicals. These fuels will run out one day because they take millions of years to form.

People must save natural resources. They should plant more trees and stop wasting water and energy. Farmers should use fewer chemicals on crops. Everyone should recycle and use renewable energy like solar and wind power. Saving resources today will help future generations live better.

Textbook solutions

Multiple Choice Questions (MCQs)

1. Gases that made the 99% of air are:

A. Nitrogen and argon
B. Oxygen and argon
C. Nitrogen and oxygen
D. Carbon dioxide and oxygen

Answer: C. Nitrogen and oxygen

2. __________ is the ultimate source of all freshwater.

A. Groundwater
B. Rain
C. Sea
D. Lake

Answer: B. Rain

3. __________ percent of the weight of living organisms is water.

A. 80%
B. 90%
C. 85%
D. 70%

Answer: B. 90%

4. Process of obtaining minerals from the earth is called __________.

A. Mining
B. Refinery
C. Liquefaction
D. Gasification

Answer: A. Mining

5. Around __________ percent of India’s bauxite reserves lie in the southern parts of Odisha.

A. 75
B. 80
C. 70
D. 85Answer: B. 80

Very Short Answer Questions

1. Describe the composition of air.

Answer: Air is composed of many gases. Nitrogen and oxygen are the major gases that make up 99% of air. Other important gases are carbon dioxide, ozone, helium, argon, methane, etc. Another constituent of air is water vapour. Dust particles are also present in the lower atmosphere.

Composition of air:

• Nitrogen – 78%
• Oxygen – 21%
• Argon – 0.9%
• Carbon dioxide – 0.03%
• Neon – 0.001%
• Helium – 0.0005%
• Ozone – 0.00006%

2. Name the major pollutants of air.

Answer: The major pollutants of air are sulphur dioxide, nitrogen oxide, carbon dioxide, fly ash, and suspended particulate matter (SPM). Smog, which is a smoky mixture of carbon monoxide and organic compounds due to incomplete burning of fossil fuels, is also a concern. Additionally, chlorofluorocarbons (CFCs), used in spray cans and refrigeration, contribute to air pollution by depleting the ozone layer.

3. What is suspended particulate matter?

Answer: Suspended particulate matter (SPM) is one of the major pollutants of air.

4. What is the chief source of water?

Answer: Rain is the ultimate source of all freshwater.

5. What is mining?

Answer: Process of obtaining minerals from the earth is called mining.

Short Answer Questions

1. Why is air pollution more in cities?

Answer: Air pollution is more severe in the urban areas as compared to rural areas. Maximum pollution can be seen in the industrial areas of the cities. Major pollutants of air are sulphur dioxide, nitrogen oxide, carbon dioxide, fly ash, and suspended particulate matter (SPM). Smog is often seen in big cities, which is a smoky mixture of carbon monoxide and organic compounds due to incomplete burning of fossil fuels. Nowadays, another pollutant called CFC (chlorofluorocarbons) is added to the air, which is used in spray cans and refrigeration and causes depletion of the ozone layer.

2. What is the role of carbon dioxide gas in air?

Answer: Carbon dioxide is used for the process of photosynthesis, therefore, required by all green plants. It also absorbs the radiant energy of the earth and re-radiates it back to the earth. Therefore, it is also called the greenhouse gas. It increases the temperature of the lower atmosphere.

3. Why is there water scarcity in big cities?

Answer: With the changing time, the availability of freshwater is decreasing. There are limited reserves of freshwater, and they too are getting polluted. Discharge of municipal and industrial sewage into water bodies contaminates the freshwater resources of the earth. When sewage is released into freshwater bodies like lakes and rivers, freshwater gets contaminated with infectious organisms and makes the water unfit for consumption. Most of the rivers of the earth are getting polluted, which also disturbs the ecosystem of water bodies. Farmers are using insecticides and pesticides, which come down with rainwater and pollute the groundwater. Water of rivers is unfit for drinking purposes, therefore, water scarcity problems are common in many big cities.

4. How much area of India is under forest cover?

Answer: At present, India has 23% of its land covered under forests.

5. What is the enrichment of minerals?

Answer: The enrichment of minerals refers to the process by which the concentration of valuable minerals in an ore is increased through various physical or chemical methods. (This answer is not there in the textbook)

6. List two uses of coal.

Answer: The two uses of coal are:

• Major use of coal is to generate power. When coal is burnt, it generates heat, and this heat is used to convert water into electricity. Steam pressure helps rotate the turbine, thus generating electricity.
• Coal is also used in the steel industry. It is first heated to convert it into coke, which is almost pure carbon. A mixture is made of iron ore, coke, and limestone, which is heated to make iron.

7. Man’s dependence on petroleum is increasing. Explain.

Answer: Petroleum is used as a fuel and as raw material in various chemical industries. The dependence of the human population on petroleum and its products is increasing day by day. Increasing population pressure has led to enormous demand for this fuel. The reservoirs beneath the surface of the earth have started going down.

8. What is the composition of natural gas?

Answer: Natural gas is also a fossil fuel made up of hydrocarbons. Its major constituents are methane (85%) and ethane (10%). Its major impurities are nitrogen, carbon dioxide, and hydrogen sulfide, which are removed during the process of refining.

9. Give two uses of natural gas.

Answer: The two uses of natural gas are:

• It is used as fuel for heating, cooking, and generating electricity.
• It is also used in kilns to bake bricks and ceramic tiles. Cement is also manufactured with its help as a fuel.

10. How is natural gas transported?

Answer: During earlier times, it was not possible to transport gas because it could not be stored. In the 19th century, it was treated as a waste by-product of petroleum. Later, technology was developed to liquefy it and transport it.

Long Answer Questions

1. What are the main sources of air pollution? Name two air pollutants.

Answer: Various human activities like transportation, industrialization, and agriculture release numerous pollutants that change the composition of air. Air pollution is more severe in urban areas compared to rural areas. Maximum pollution can be seen in the industrial areas of the cities.

Major pollutants of air are sulphur dioxide, nitrogen oxide, carbon dioxide, fly ash, and suspended particulate matter (SPM). Smog is often seen in big cities, which is a smoky mixture of carbon monoxide and organic compounds due to the incomplete burning of fossil fuels. Nowadays, another pollutant called CFC (chlorofluorocarbons) is added to the air. It is a chemical used in spray cans and refrigeration and causes depletion of the ozone layer.

2. Discuss the various uses of air.

Answer: Air is a mixture of gases around any celestial body. The gravitational pull of that celestial body prevents the gases or air from escaping. Our earth has gravitational pull; therefore, the air remains attached to it.

Uses of air:

• Oxygen is the most important of all the gases as it is a life-supporting gas for all organisms.
• Nitrogen is the largest constituent. It is chemically inactive and acts as a diluent.
• Carbon dioxide is used for the process of photosynthesis, therefore, required by all green plants. It also absorbs the radiant energy of the earth and re-radiates it back to the earth. Therefore, it is also called a greenhouse gas. It increases the temperature of the lower atmosphere.
• Ozone gas absorbs the ultraviolet rays of the sun and thus prevents the earth from becoming too hot. Its other uses are water purifying, bleaching food, and sterilizing air.
• Water vapors become heavy on cooling. Dust particles help in bringing rainfall because when water vapors become heavy after cooling, they deposit on dust particles.

3. What is the difference between evaporation and condensation?

Answer: Evaporation is the process where a liquid turns into a gas or vapor due to an increase in temperature or exposure to air, typically occurring at the surface of the liquid. Condensation, on the other hand, is the process where a gas or vapor cools down and changes back into a liquid, usually when it comes into contact with a cooler surface or environment. (This answer is not there in the textbook)

4. Explain the various uses of water.

Answer: Water is an essential resource for life on the planet Earth. No organism can function without water. It is also a major constituent of living matter, with 50 to 90% of the weight of living organisms being water. Around 71% of the Earth’s surface is covered with water, but 97% of this water is contained in the oceans and is saline, making it unsuitable for direct use. Freshwater, which is found in rivers, glaciers, groundwater, and lakes, is the only usable form. Rain is the ultimate source of all freshwater. The level of groundwater is continuously falling due to deforestation and excessive irrigation. Efforts should be made to recharge groundwater through watershed management.

Uses of water:

• Among the various gifts of nature to man, water is a precious one. Apart from giving life to all organisms, it is also a raw material for many industries.
• It can dissolve most substances, making it useful for diluting and removing waste.
• When water is made to fall on turbines, it generates hydel power, which is used as energy in the fast-developing world. The method of power generation through water is a pollution-free method.
• Water, being a cheap means of transport, is widely used in international trade.

Present status of water:

• With time, the availability of freshwater is decreasing.
• There are limited reserves of freshwater, and they are getting polluted.
• Discharge of municipal and industrial sewage into water bodies contaminates Earth’s freshwater resources.
• When sewage is released into freshwater bodies like lakes and rivers, freshwater gets contaminated with infectious organisms, making it unfit for consumption.
• Most of the rivers on Earth are getting polluted, disturbing the ecosystem of water bodies.
• Aquatic life is exposed to danger.
• Farmers use insecticides and pesticides, which come down with rainwater and pollute groundwater.
• The water of rivers is unfit for drinking purposes, leading to water scarcity problems in many big cities.

5. Discuss the composition of soil.

Answer: Soil supports all plant life of the earth’s crust. The nature and amount of plant life depend upon the soil of that area. It acts as a storage reservoir for water and other plant nutrients. The loose material of soil consists of organic and inorganic material. The inorganic material is derived from the rocks that have broken down by various means. The organic material is derived from the debris of plants and other life forms like microorganisms. Inorganic matter and organic matter make up 50% of the volume of soil. The remaining 50% is pore space, which is the open space between the soil particles. It allows water and air to move in the soil.

Humus is an odourless, amorphous, homogeneous dark-colored material. The end products of its decomposition are carbon dioxide, ammonia, and mineral salts.

6. Do modern agricultural activities pollute the soil? How?

Answer: Soil pollution is the building-up of toxic compounds or pollutants in the soil. It affects the plant and animal life in the soil. Pathogens or disease-causing organisms also develop in the soil. Farmers treat the soil with fertilizers, insecticides, pesticides, fungicides, herbicides, etc., which disturb the growth of bacteria, fungi, and other organisms. The formation of humus stops. Dumping of industrial and municipal wastes also spoils the soil condition. Many pollutants are released from these wastes that contaminate the soil.

7. Describe the various uses of forests.

Answer: Forests provide habitat to numerous species of plants and animals. All inhabitants get food and protection from the forests. They help in protecting the soil from erosion. Forests store a large amount of water, which acts as a buffer for the ecosystem during dry periods. They play a vital role in atmospheric circulation and thus control the global climate. The leaves of trees absorb carbon dioxide and release oxygen, a phenomenon that is vital for all life on Earth. Forests provide timber to humans for various activities like construction. They are a source of edible fruits and nuts. Numerous waxes and oils are also obtained from forests. The sap of many trees is used as a raw material to manufacture a variety of goods. The bark of some trees is used to make cork and medicines. A variety of chemicals are procured from forests for use in tanning leather, inks, dyes, medicines, alcohol, etc.

8. Differentiate between coal and coke.

Answer: Coal is the largest conventional fossil fuel. It is a combustible organic rock composed of carbon, oxygen, and hydrogen. It was formed in the Carboniferous period (360 million–290 million years ago) when plants died, decomposed, and remained buried in the earth’s crust. Continuous heat and weight converted this matter into coal. Coal is rich in hydrocarbons and is also called a fossil fuel.

Coke is almost pure carbon and is produced by heating coal. It is used in the steel industry. A mixture of iron ore, coke, and limestone is heated to make iron. During the process of coke formation, various types of gases are released, which are used in industries like fertilizer, pesticide, and medicine.

9. Describe the major uses of natural gas.

Answer: Natural gas is a major source of energy. It is used in industries for heating and power generation. It is also used in kilns to bake bricks and ceramic tiles. Cement is also manufactured with its help as a fuel. Other uses of gas as fuel include glass making, food processing, and making steam in water boilers. Natural gas is also used as a raw material in industries. As a raw material, its major use is in the manufacturing of petrochemicals. These chemicals are derived from gas and petroleum. Petrochemicals are used in fertilizers, medicines, detergents, plastics, etc.

Extras

Additional questions and answers

1. Define natural resources?

Answer : Natural resources are the components of the natural environment that can be drawn upon for the benefits of human beings. Any component of the natural environment which can be drawn upon for the survival, development, and prosperity of human beings is called a natural resource.

Q. Give two examples of inexhaustible natural resources?

Answer : Two examples of inexhaustible natural resources are sunlight and wind.

Q. What do you understand by exhaustible natural resources?

Answer : Exhaustible natural resources are those resources which cannot be renewed and can go off if used in excess or overused.

Q. Name two renewable resources?

Answer : Two renewable resources are soil and water.

Q. Give two examples of non-renewable resources?

Answer : Two examples of non-renewable resources are coal and petroleum.

Q. What are the main uses of solar energy?

Answer : The main uses of solar energy are: (i) It is used for heating water and generating electricity. (ii) Solar photovoltaic (PV) cells directly produce electricity from sunlight. (iii) Solar radiations can produce high temperature, which can generate electricity.

Q. Mention any two gadgets powered by solar energy.

Answer : Two gadgets powered by solar energy are: (i) Solar cookers
(ii) Solar water heaters

Q. Name the gases that constitute 99% of the atmosphere.

Answer : The gases that constitute 99% of the atmosphere are nitrogen and oxygen.

Q. Define aerosols.

Answer : Aerosols are very small airborne suspensions which may be solid or liquid.

Q. What is smog?

Answer : Smog is a smoky mixture of carbon monoxide and organic compounds due to incomplete burning of fossil fuels.

Q. What is the function of ozone gas?

Answer : Ozone gas absorbs the ultraviolet rays of the sun and thus prevents the earth from becoming too hot. Its other functions include water purifying, bleaching food, sterilizing air, etc.

Q. Define groundwater.

Answer : Groundwater is the water found beneath the earth’s surface, contained in layers of soil, sand, and rock. It is a major source of freshwater used for drinking, irrigation, and other purposes.

Q. Define siltation.

Answer : Siltation is the process where eroded soil deposits in rivers, dams, and other water bodies. This causes the water level to rise and leads to floods. With continuous siltation, the water storage capacity of dams falls.

Q. What are mineral ores?

Answer : Mineral ores are minerals that are rich in the elements of any metal and can be concentrated and refined through different chemical processes to extract metals.

Q. What do you mean by soil erosion?

Answer : Soil erosion is the removal of topsoil by natural agents like wind, rivers, etc. It is directly related to deforestation. When trees are cut, the soil becomes bare and is easily carried away by wind or water.

Q. Name the major constituents of natural gas?

Answer : The major constituents of natural gas are methane (85%) and ethane (10%).

Q. Define fossil fuel?

Answer : Fossil fuel is a naturally available substance composed of hydrocarbons, formed over millions of years from the remains of ancient plants and animals. Coal, petroleum, and natural gas are examples of fossil fuels.

Q. What is the main chemical composition of petroleum?

Answer : The main chemical composition of petroleum is hydrocarbons, with some amount of sulphur and oxygen also present.

Q. What is the importance of natural resources for human development?

Answer : The development of a country depends upon the resource availability. Natural resources are the components of the natural environment that can be drawn upon for the benefits of human beings. Resources do not refer to a thing but the function that it performs, meaning a thing becomes a resource only when it is used by man to perform a function.

Q. Differentiate between renewable and non-renewable resources.

Answer : Renewable resources are those which are regularly replenished through natural processes and, therefore, have the potential to last indefinitely, for example, water, air, forests, sunlight, etc. Non-renewable resources exist in fixed amounts and may finish in the future because they are not regularly replenished, for example, coal, petroleum, natural gas, and many other mineral ores.

Q. Explain briefly how wind energy is used.

Answer : Wind energy is used for grinding grains, lifting water, and propelling ships. It has low environmental impacts like bird kills, noise, effect on TV reception, etc. India is considered to be the third largest producer of wind energy in the world.

Q. Why is air pollution more severe in urban areas?

Answer : Air pollution is more severe in urban areas as compared to rural areas. Maximum pollution can be seen in the industrial areas of the cities. Various human activities like transportation, industrialization, agriculture, etc., release numerous pollutants that change the composition of air.

Q. State two reasons why water is essential for life.

Answer : (i) Water is a major constituent of living matter, making up 50 to 90% of the weight of living organisms.
(ii) It is life-supporting for all organisms and acts as a raw material for many industries.

Q. Why is groundwater continuously declining?

Answer : The level of groundwater is continuously falling down due to deforestation and excessive irrigation.

Q. Why is groundwater continuously declining?

Answer : The level of groundwater is continuously falling down due to deforestation and excessive irrigation.

Q. Describe briefly the role of water in power generation.

Answer : When water is made to fall on turbines, it generates hydel power, which is used as energy in the fast-developing world. The method of power generation through water is a pollution-free method.

Q. How do dust particles contribute to rainfall?

Answer : Dust particles help in bringing rainfall because when water vapours become heavy after cooling, they deposit on dust particles.

Q. Explain the importance of nitrogen in the atmosphere?

Answer : Nitrogen is the largest constituent of air and is chemically inactive, acting as a dilutent. It makes up 78% of the air and, along with oxygen, constitutes 99% of the atmosphere.

Q. Why are rivers becoming polluted?

Answer : Rivers are becoming polluted due to the discharge of municipal and industrial sewage into water bodies, which contaminates freshwater resources. When sewage is released into rivers, the water gets contaminated with infectious organisms, making it unfit for consumption. Additionally, farmers use insecticides and pesticides that wash down with rainwater, further polluting the river water.

Q. What are the effects of soil pollution?

Answer : The effects of soil pollution include the building-up of toxic compounds or pollutants in the soil, which affects plant and animal life. Pathogens or disease-causing organisms develop in the soil. Farmers treat the soil with fertilizers, insecticides, pesticides, fungicides, and herbicides, which disturb the growth of bacteria, fungi, and other organisms. The formation of humus stops, and dumping of industrial and municipal wastes spoils the soil condition. Many pollutants released from these wastes contaminate the soil.

Q. Explain two uses of forests other than timber.

Answer : (i) Forests store a large amount of water which acts as a buffer for the ecosystem during dry periods and play a vital role in atmospheric circulation, thus controlling the global climate.
(ii) Forests provide habitat to numerous species of plants and animals, offering them food and protection while also helping in protecting the soil from erosion.

Q. Why are forest covers crucial for maintaining global climate?

Answer : Forests play a vital role in atmospheric circulation and thus control the global climate. The leaves of trees absorb carbon dioxide and release oxygen, a phenomenon that is vital for all life on Earth.

Q. State two reasons for the depletion of petroleum reserves.

Answer : (i) Increasing population pressure has led to an enormous demand for this fuel.
(ii) The reservoirs beneath the surface of the Earth have started going down due to overexploitation.

Q. Explain the classification of natural resources.

Answer : Natural resources are classified into two main groups: inexhaustible and exhaustible natural resources. Inexhaustible natural resources are those which can be renewed after some time and do not get exhausted, such as sunlight, wind, and tidal energy. Exhaustible natural resources, on the other hand, are those which cannot be renewed and may get used up if overused. These are further divided into renewable and non-renewable resources. Renewable resources, like soil, water, wild animals, and plants, are regularly replenished through natural processes and have the potential to last indefinitely. Non-renewable resources, such as minerals, coal, petroleum, and natural gas, exist in fixed amounts and may finish in the future because they are not regularly replenished.

Q. What is the present status of air pollution in cities?

Answer : Air pollution is more severe in urban areas compared to rural areas. Maximum pollution can be seen in the industrial areas of cities. Major pollutants of air include sulphur dioxide, nitrogen oxide, carbon dioxide, fly ash, and suspended particulate matter (SPM). Smog, a smoky mixture of carbon monoxide and organic compounds due to incomplete burning of fossil fuels, is often observed in big cities. Additionally, another pollutant called CFC (chlorofluorocarbons), used in spray cans and refrigeration, has been added to the air, causing depletion of the ozone layer.

Q. Discuss the major pollutants of air and their sources.

Answer : The major pollutants of air and their sources are:
(i) Sulphur dioxide, which is released from industrial activities and the burning of fossil fuels.
(ii) Nitrogen oxide, produced mainly from vehicle emissions and industrial processes.
(iii) Carbon dioxide, emitted through the burning of fossil fuels, deforestation, and industrial activities.
(iv) Fly ash, a byproduct of coal combustion in thermal power plants and other industrial processes.
(v) Suspended particulate matter (SPM), which includes tiny particles released from construction activities, vehicular emissions, and industrial processes.
(vi) Smog, a smoky mixture of carbon monoxide and organic compounds formed due to the incomplete burning of fossil fuels, often seen in big cities.
(vii) Chlorofluorocarbons (CFCs), chemicals used in spray cans and refrigeration that contribute to ozone layer depletion.

Q. Explain the importance and uses of water.

Answer : The importance and uses of water are:

(i) Water is essential for life on Earth, as no organism can function without it.
(ii) It is a major constituent of living matter, making up 50 to 90% of the weight of living organisms.
(iii) Water serves as a raw material for many industries.
(iv) It has the ability to dissolve most substances, making it useful for diluting and removing waste.
(v) When made to fall on turbines, water generates hydel power, which is a pollution-free method of energy production.
(vi) Water is a cheap means of transport and is widely used in international trade.

Q. What are the current issues affecting freshwater availability?

Answer : The current issues affecting freshwater availability are:

(i) The availability of freshwater is decreasing with changing time. (ii) There are limited reserves of freshwater, and they too are getting polluted. (iii) Discharge of municipal and industrial sewage into water bodies contaminates the freshwater resources of the earth. (iv) When sewage is released into freshwater bodies like lakes and rivers, freshwater gets contaminated with infectious organisms, making the water unfit for consumption. (v) Most of the rivers on earth are getting polluted, disturbing the ecosystem of water bodies. (vi) Aquatic life is exposed to danger due to pollution. (vii) Farmers using insecticides and pesticides contribute to groundwater pollution as these chemicals come down with rainwater. (viii) The water of rivers is unfit for drinking purposes, leading to water scarcity problems in many big cities.

Q. Discuss the factors responsible for soil pollution.

Answer : The factors responsible for soil pollution are:

(i) Soil pollution is caused by the building-up of toxic compounds or pollutants in the soil.
(ii) It affects plant and animal life in the soil, and pathogens or disease-causing organisms develop in the soil.
(iii) Farmers treating the soil with fertilizers, insecticides, pesticides, fungicides, and herbicides disturb the growth of bacteria, fungi, and other organisms.
(iv) The formation of humus stops, and dumping of industrial and municipal wastes spoils the soil condition.
(v) Many pollutants released from these wastes contaminate the soil.

Q. Explain the importance of soil for plant life?

Answer : Soil supports all plant life of the earth’s crust. The nature and amount of plant life depend upon the soil of that area. It acts as a storage reservoir for water and other plant nutrients. It is a medium for plant growth, allows transport of water and nutrients to the roots, provides habitat for many soil organisms, offers air for gaseous exchange between roots and the atmosphere, holds water, and maintains adequate aeration.

Q. How does soil erosion affect the environment?

Answer : Soil erosion affects the environment by removing the topsoil through natural agents like wind and rivers. This process is directly related to deforestation, as cutting trees leaves the soil bare, making it easily carried away. The eroded soil deposits in rivers, dams, and other water bodies, causing siltation. Siltation raises the water level, leading to floods and reducing the water storage capacity of dams. Additionally, soil erosion disturbs ecosystems, causes loss of habitat for organisms, increases soil pollution, and contributes to falling groundwater levels.

Q. Discuss briefly the role of forests in supporting biodiversity.

Answer : Forests play a vital role in supporting biodiversity as they provide habitat to numerous species of plants and animals. All inhabitants get food and protection from the forests. They also help in protecting the soil from erosion, store a large amount of water which acts as a buffer for ecosystems during dry periods, and play a crucial role in atmospheric circulation, thereby controlling the global climate. The leaves of trees absorb carbon dioxide and release oxygen, a phenomenon that is essential for all life on Earth.

Q. Explain the present status of forests in India and globally.

Answer : In India, 23% of the land is currently covered under forests, while globally, around 26% of the land is covered under forest cover, as per data provided by the Food and Agriculture Organization (FAO) of the UNO. The more land that is under forest, the better the environment functions since forests provide habitat to numerous plants and animals. However, many areas in the world are experiencing heavy deforestation, leading to ecosystem disturbances, loss of habitat for many organisms, increased soil erosion, falling groundwater levels, and several other environmental problems.

Q. What are the main uses and composition of coal?

Answer : Coal is a combustible organic rock composed of carbon, oxygen, and hydrogen. It is rich in hydrocarbons and is also referred to as fossil fuel. The major uses of coal include generating power by burning it to produce heat, which converts water into electricity through steam pressure that rotates turbines. Coal is also used in the steel industry, where it is first heated to convert it into coke, which is almost pure carbon. A mixture of iron-ore, coke, and limestone is heated to make iron. During coke formation, various gases are released, which are utilized in industries like fertilizers, pesticides, medicines, etc. Techniques are employed to convert coal into gaseous or liquid forms, which can be transported and used as fuel.

Q. Explain briefly the process of petroleum extraction using modern technology.

Answer : Modern technology has stepped up the oil extraction from the earth. One such method is water injection, in which water is injected into the oil well. This builds pressure in the well, and since petroleum is lighter, it comes up, increasing efficiency by 60%. In cases where oil is thick or viscous, steam injection technology is applied. This not only increases pressure but also raises the temperature, making the oil flow more easily.

46. Why is natural gas considered an important energy source?

Answer : Natural gas is considered an important energy source because it is a fossil fuel made up of hydrocarbons, with its major constituents being methane (85%) and ethane (10%). It is used as a fuel in various applications such as running machinery, auto-vehicles, kilns for baking bricks and ceramic tiles, cement manufacturing, glass making, food processing, and generating steam in water boilers. Additionally, it serves as a raw material in industries, particularly for manufacturing petrochemicals, which are used in fertilizers, medicines, detergents, plastics, and more.

Additional MCQs

1. Natural resources become resources only when they are:

A. Found in nature
B. Used by humans
C. Inexhaustible
D. Renewable

Answer: B. Used by humans

Q. Natural resources that can be renewed and do not run out are called:

A. Exhaustible
B. Non-renewable
C. Inexhaustible
D. Mineral resources

Answer: C. Inexhaustible

Q. Which one is an example of an inexhaustible resource?

A. Coal
B. Wind
C. Petroleum
D. Minerals

Answer: B. Wind

Q. What are exhaustible natural resources?

A. Always renewable
B. Cannot be renewed
C. Replenished naturally
D. Permanently available

Answer: B. Cannot be renewed

Q. Which resource is renewable?

A. Coal
B. Petroleum
C. Natural gas
D. Forests

Answer: D. Forests

Q. Which gas forms the largest component of air?

A. Oxygen
B. Nitrogen
C. Carbon dioxide
D. Argon

Answer: B. Nitrogen

Q. Which gas supports life on earth?

A. Nitrogen
B. Oxygen
C. Carbon dioxide
D. Argon

Answer: B. Oxygen

Q. Which gas is considered a greenhouse gas?

A. Nitrogen
B. Oxygen
C. Carbon dioxide
D. Helium

Answer: C. Carbon dioxide

Q. Which gas in the atmosphere absorbs ultraviolet rays?

A. Carbon dioxide
B. Oxygen
C. Nitrogen
D. Ozone

Answer: D. Ozone

Q. Major pollutants of air include sulphur dioxide, carbon dioxide, and:

A. Methane
B. Hydrogen
C. Argon
D. Fly ash

Answer: D. Fly ash

Q. Smog is primarily associated with which area?

A. Rural
B. Urban
C. Mountainous
D. Desert

Answer: B. Urban

Q. Chlorofluorocarbons (CFCs) primarily cause depletion of:

A. Nitrogen levels
B. Oxygen
C. Carbon dioxide
D. Ozone layer

Answer: D. Fly ash

Q. Earth’s surface is covered by water up to:

A. 61%
B. 71%
C. 81%
D. 91%

Answer: B. 71%

Q. Usable freshwater mainly comes from:

A. Oceans
B. Rivers and lakes
C. Glaciers
D. Rain

Answer: B. Rivers and lakes

Q. The water in oceans is unusable directly because it is:

A. Polluted
B. Saline
C. Warm
D. Frozen

Answer: B. Rivers and lakes

Q. Groundwater levels are falling mainly due to:

A. Global warming
B. Deforestation
C. Heavy rainfall
D. Snow melting

Answer: B. Deforestation

Q. Organic substances in sewage are measured by:

A. Chemical Oxygen Demand
B. Biochemical Oxygen Demand
C. Organic Oxygen Level
D. Microbial Demand Level

Answer: B. Biochemical Oxygen Demand

Q. Soil erosion is increased significantly by:

A. Excess rainfall
B. Industrial waste
C. Over-irrigation
D. Deforestation

Answer: D. Deforestation

Q. Erosion leading to deposition of soil in water bodies is called:

A. Deposition
B. Siltation
C. Weathering
D. Accretion

Answer: B. Siltation

Q. Which of the following is a combustible organic rock?

A. Petroleum
B. Natural gas
C. Coal
D. Methane

Answer: A. Petroleum

Q. The formation of coal occurred during which period?

A. Cretaceous
B. Jurassic
C. Carboniferous
D. Permian

Answer: C. Carboniferous

Q. At current rates, coal reserves are estimated to last approximately:

A. 50 years
B. 100 years
C. 200 years
D. 500 years

Answer: C. 200 years

Q. The primary constituent of natural gas is:

A. Ethane
B. Methane
C. Propane
D. Butane

Answer: A. Methane

Q. Which substance is commonly used to liquefy petroleum underground for extraction?

A. Carbon dioxide
B. Nitrogen
C. Water
D. Oxygen

Answer: C. Water

Q. India’s forest cover is approximately:

A. 20%
B. 23%
C. 26%
D. 30%

Answer: B. 23%

Q. What percentage of the world’s land is under forest cover according to FAO?

A. 20%
B. 23%
C. 26%
D. 30%

Answer: C. 26%

Q. Which element is predominant in coal?

A. Oxygen
B. Carbon
C. Hydrogen
D. Sulphur

Answer: B. Carbon

Q. Major uses of coal include power generation and:

A. Agriculture
B. Cement industry
C. Steel industry
D. Textile industry

Answer: C. Steel industry

Q. Which method improves irrigation efficiency?

A. Surface irrigation
B. Drip irrigation
C. Canal irrigation
D. Flood irrigation

Answer: B. Drip irrigation

Q. Soil erosion primarily increases due to:

A. Rainfall
B. Wind
C. Deforestation
D. Fertilizer use

Answer: B. Deforestation

31. The process of extracting minerals from the earth is known as:

A. Drilling
B. Mining
C. Excavating
D. Refining

Answer: B. Mining