WBBSE Solutions For Class 10 Physical Science And Environment Chapter 1 Environmental Concern

Chapter 1 Environmental Concern Topic A Atmosphere Synopsis:

WBBSE Class 10 Environmental Concerns Overview

Atmosphere: The gaseous layer surrounding the surface of the earth that extends up to about 1600 km, is known as the atmosphere.

Different layers of the atmosphere: On the basis of temperature and pressure, the atmosphere is divided into five different layers namely troposphere, stratosphere, mesosphere, thermosphere, and exosphere.

Convection current: On heating, fluids (liquids and gases) undergo expansion, and hence their density decreases. So, the heated liquid or gas becomes lighter and moves upward. On the other hand, the cool heavy part of the upper region comes down. This results in the formation of circular current which is known as convection current.

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Wind and storm: Wind blows from a region of comparatively higher pressure to a region of comparatively lower pressure. Earth surface, under certain circumstances, gets heated up. Hence the air adjacent to this earth surface also gets heated up and moves upward.

This creates a low pressure zone in that, region. Cooler air from surroundings rushes towards that region. Greater the difference in air pressure, faster the movement of air from the higher to lower pressure region. Thus wind is created. When wind blows above a specified speed, it is termed as a storm.

Chapter 1 Environmental Concern Topic A Atmosphere Short And Long Answer Type Questions:

Question 1. What is the atmosphere? What are the different regions of the atmosphere?
Answer:

Atmosphere:

The gaseous layer surrounding the surface of the earth which extends up to about 1600 km, is known as the atmosphere. Under the influence of gravity, this surrounding remains attached to the surface of the earth. On the basis of height and temperature, the atmosphere is divided into five different regions.

Layers	Height from the earth’s surface	Temperature Range (°C)
Tropo- sphere	0- 12 km	+15 to -60 (temperature increases with the. increase in height)
Strato- sphere	12 – 45 km	-60 to 0 (temperature increases with the increase of height)

 

Layers	Height from the earth’s surface	Temperature Range (°c)
Meso- sphere	45-85 km	0 to -100 (temperature increases with the increase in height)
Thermo- sphere	85 – 500 km	-100 to +1200 (temperature increases with the increase in height)
Exo- sphere	500 -1000 km	> 1200

 

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Question 2. What are the ‘homosphere’ and ‘heterosphere’ of the atmosphere?
Answer:

The ‘homosphere’ and ‘heterosphere’ of the atmosphere:

The lower part of the atmosphere (extends up to an approximate height of 85 km above the earth surface) is homogeneous in nature. The gaseous components ( N_2, O_2, Ar, CO_2, water vapor etc.) are evenly distributed in this, region. This part of the atmosphere is called the homosphere.

The remaining part of the atmosphere above the homosphere where the components are unevenly distributed is called the heterosphere. This part starts just above the homosphere region and extends between 85km above the earth’s surface up to a distance of 1000 km.

Question 3. Define troposphere. Why is it called turbulent sphere’?
Answer:

Troposphere:

The lowest layer of the atmosphere is called the troposphere. It extends from the sea level up to a height of about 12 km. This layer contains dust particles, water vapour, clouds etc. Different natural phenomena like storms, rains, lightning, thunderstorms etc., occur in this region. So, it is also known as the turbulent sphere.

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Question  4. What is the stratosphere? Why is it dynamically stable?
Answer:

Stratosphere:

The atmospheric layer that extends up to a height of 45 km above the troposphere is known as stratosphere.

There is very little air in this region and dust particles, water vapor etc. are absent in this layer. Hence, this layer is free of several associated turbulence like clouds, rains, lightning, thunderstorms etc. Thus, it is dynamically stable.

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Question 5. What is the mesosphere? Name the top layer of the mesosphere.
Answer:

Mesosphere:

The atmospheric layer present just above the stratosphere and extends up to a height of 85 km below the thermosphere is known as the mesosphere. The top layer of the mesosphere is known as mesopause. Temperature remains fixed (-92°C) in this region.

Question 6. What is the thermosphere? Why is it named so?
Answer:

Thermosphere:

The atmospheric layer present just above the mesosphere and extends up to a height of 500 km is known as thermosphere.

The temperature of this layer tends to increase abruptly with increasing altitude. At a height of about 120 km the temperature is about 500°C, at a height of 200 km the temperature becomes almost 700°C and at 480 km the temperature is about 1232°C. Therefore, this layer is called thermosphere.

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Question 7. What is ionosphere? Why Is it named so?
Answer:

Ionosphere:

The particular portion of thermosphere which contains several gaseous ions is known as ionosphere.

Cosmic radiation, X-rays, and gamma rays coming from the Sun ionizes the gases (mainly nitrogen and oxygen) of this region. As a result, this particular region contains large number of ions and free electrons. Due to the high concentration of ions in this region, this is called ionosphere.

Question 8. What is meant by ‘aurora’? What are ‘aurora Borealis and ‘aurora australis’?
Answer:

‘Aurora’:

Cosmic radiations, X-rays, gamma rays coming from the sun ionizes the gases present in ionosphere (a specific portion of thermosphere) and produce large number of ions as well as free electrons.

These charged particles undergo interactions with the magnetic field of the earth. As a result of this interactions, bright lights appear in the sky of polar regions. These polar lights or natural light displays in the earth’s sky is commonly known as aurora.

The aurora formed in the sky of north pole is known as aurora borealis and the aurora formed in the sky of south pole is called aurora australis.

Question 9. Give a brief description of the exosphere layer of atmosphere.
Answer:

The exosphere layer of atmosphere:

The atmospheric layer situated at a height of more than 500 km with respect to the surface of earth is called exosphere. It extends up to an altitude of about 1000 km. The temperature in this region is more than 1200°C. This layer contains hydrogen and. helium gases. Artificial satellites and space stations are located at this layer.

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Question 10. How does atmospheric pressure change with the increase in altitude?
Answer:

As we move up from the sea level, density of air decreases, and hence, atmospheric pressure also decreases.

Generally, with every 110 m rise in height, air pressure decreases by 1cm. However, the rate of change of pressure is not uniform at the upper layer of the atmosphere.

Question 11. Discuss how temperature change in different layers of the atmosphere as the distance from the earth’s surface increases.
Answer:
1. The troposphere gets colder with the increase in altitude. With each km rise in altitude, the temperature falls by 6.5°C. The top layer of troposphere has a temperature of about -56°C.

2. With increasing altitude, the temperature of stratosphere gradually increases and temperature becomes 0°C at the top.

3. Mesosphere is the coldest region of atmosphere. Temperature decreases as we move upward along this layer.

4. In the thermosphere, temperature gradually increases with increasing height. This layer absorbs cosmic radiation coming from the Sun and is heated up. ConseQuestionuently, its temperature reaches up to 1200°C. The temperature of exosphere is higher than 1200°C.

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Question 12. Why does temperature increase with increasing height at the stratosphere?
Answer:

The oxygen molecules present in stratosphere is dissociated into atomic oxygen by absorbing the UV rays of the sun. These oxygen atoms then combine with molecular oxygen to form ozone (O₃) molecules.

The last step is highly exothermic in nature and produces a large amount of heat. As a result, the temperature of this layer increases gradually with increase in height and reaches at a temperature around 0°C at the top of the layer.

Question 13. What is convection? What is convection current?
Answer:

Convection: The process by which the heated molecules of a liquid or a gas move from a region of higher temperature to a region of lower temperature thus carrying heat energy, is called convection.

Convection current: When a liquid or gas is heated, its density decreases due to expansion The heated liquid or gas thus becomes lighter and moves upward. Comparatively colder and heavier liQuestionuid or gas from the surroundings then rushes towards that region to fill up the vacuum. Such circulation of gaseous or liQuestionuid layer results in the formation of a convection current.

Question 14. How is convection current formed in air?
Answer: If the earth’s surface becomes hot the air adjacent to the earth’s surface also gets heated up. Hence it becomes lighter and rises up. This creates a low-pressure zone in that region. Cold air from surroundings then rushes towards that region to fill up the vacuum. This creates a convection current.

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Question 15. Give two natural phenomena where a convection current is observed. When do they have maximum intensity?
Answer:

Convection current is observed in land breeze and sea breeze. The inland breeze blows during the night and intensifies around the dawn. On the other hand, sea breeze blows at the morning and intensifies around dusk.

Question 16. Describe the formation of land breeze.
Answer:

The formation of land breeze:

At night, the landmass in the coastal area loses heat at a faster rate than the sea water. Hence, the water remains comparatively warmer at night. ConseQuestionuently, warm air above the sea becomes lighter and rises up while cold and dense air from the landmass starts moving towards the sea. This is known as land breeze.

Question 17. Describe the formation of the sea breeze.
Answer:

The formation of the sea breeze:

The specific heat of water is high, due to this the land in the coastal areas get heated up in a Questionuicker manner compared to the seawater. As a result, the air above the landmass becomes lighter and rises up, thereby creating a low-pressure zone. The cold, denser air from the sea then flies into this region resulting in the sea breeze.

Question 18. How is a storm formed?
Answer:

Formation Of Storm

Wind blows from a higher-pressure region to a lower pressure region. The earth surface under certain circumstances get heated up so Questionuickly that the air adjacent to the earth’s surface becomes warmer and lighter. Hence it goes upward creating a vacuum. As a result a low pressure zone is created in that region.

The air from the surroundings then rushes towards that region. Greater the difference in air pressure, the faster the air blows from higher to the lower-pressure region. When wind blows above a specified speed, it is termed as a storm.

Chapter 1 Environmental Topic A Atmosphere Very Short Answer Type Questions Choose The Correct Answer:

Question 1. The layer of the atmosphere having the highest density is
1. Troposphere
2. Stratosphere
3. Mesosphere
4. Thermosphere

Answer: 1. Troposphere

Question 2. The layer of atmosphere in which natural phenomena such as storms, rains, and lightning occur is
1. Thermosphere
2. Troposphere
3. Stratosphere
4. Mesosphere

Answer: 2. Troposphere

Question 3. In the atmosphere, the percentage (by mass) occupied by the troposphere is
1. 25
2. 50
3. 75
4. 60

Answer: 3. 75

Question 4. The layer which is characterized by its calmness is
1. Troposphere
2. Stratosphere
3. Mesosphere
4. Thermosphere

Answer: 2. Stratosphere

Question 5. The temperature at the topmost level of the stratosphere is
1. 50°C
2. -50°C
3. 0°C
4. -30°C

Answer: 3. 0°C

Question 6. The atmospheric layer that absorbs ultraviolet rays is
1. Troposphere
2. Ozonosphere
3. Thermosphere
4. Mesosphere

Answer: 2. Ozonosphere

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Question 7. The hottest layer of the atmosphere is
1. Exosphere
2. Ozonosphere
3. Ionosphere
4. Thermosphere

Answer: 1. Exosphere

Question 8. In which atmospheric region does aurora form?
1. Ozonosphere
2. Ionosphere
3. Tropopause
4. Mesosphere

Answer: 2. Ionosphere

Question 9. The atmospheric layers where temperature increases with increasing altitude are
1. Troposphere and thermosphere
2. Mesosphere and stratosphere
3. Thermosphere and mesosphere
4. Stratosphere and thermosphere

Answer: 4. Stratosphere and thermosphere

Question 10. The atmospheric layer in which the radio waves get reflected is
1. Stratopause
2. Ozonosphere
3. Ionosphere
4. Mesosphere

Answer: 3. Ionosphere

Question 11. For each kilometer rise in altitude from the earth’s surface, the troposphere gets colder by
1. 5.6°C
2. 6.5°C
3. 3.5°C
4. 4.6°C

Answer: 2. 6.5°C

Question 12. Artificial satellites and space stations are located at the
1. Eexosphere
2. Thermosphere
3. Mesosphere
4. Stratosphere

Answer: 1. Eexosphere

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Question 13. Which layer of the atmosphere controls temperature and water cycle?
1. Stratosphere
2. Thermosphere
3. Troposphere
4. Mesosphere

Answer: 3. Troposphere

Question 14. The intensity of land breeze increases
1. Around dawn
2. Around noon
3. Around dusk
4. At night

Answer: 1. Around dawn

Question 15. The layer of the atmosphere that can be called as ‘Natural Solar Screen’ is
1. Troposphere
2. Ozonosphere
3. Thermosphere
4. Exosphere

Answer: 2. Ozonosphere

Wbbse Class 10 Physical Science And Environment

Question 16. Several ions are present in
1. Troposphere, stratosphere
2. Troposphere, mesosphere
3. Mesosphere, thermosphere
4. Stratosphere, exosphere

Answer: 3. Mesosphere, thermosphere

Question 17. The average height of the troposphere from earth’s crust
1. 18 km
2. 15 km
3. 12 km
4. 20 km

Answer: 3. 12 km

Question 18. In which layer of the atmosphere the amount of water vapor is the highest
1. Troposphere
2. Stratosphere
3. Thermosphere
4. Mesosphere

Answer: 1. Troposphere

Question 19. X-ray is absorbed in the layer called
1. Troposphere
2. Mesosphere
3. Ionosphere
4. Exosphere

Answer: 3. Ionosphere

Question 20. Gases that are present in the exosphere are
1. He, H₂
2. N_2, O₂
3. N₂, H2
4. H₂, O₂

Answer: 1. He, H₂

Question 21. The coldest region of the atmosphere is
1. Stratosphere
2. Exosphere
3. Mesosphere
4. Thermosphere

Answer: 3. Mesosphere

Chapter 1 Environmental Concern Topic A Atmosphere Answer In Brief

Types of Environmental Pollution

Question 1. State the range of troposphere in the polar region and eQuestionuatorial region.
Answer: In the polar region, troposphere extends from sea level up to a height of 8-9 km and in the eQuestionuatorial region it extends up to 16-18 km.

Question 2. What is tropopause?
Answer:

Tropopause

The narrow region, at a height of 12km from the earth’s surface, where troposphere meets stratosphere is known as the tropopause. In this region, the temperature remains unaltered with the increase in height.

Question 3. What is the air pressure at the lowest part of the troposphere?
Answer: The air pressure at the lowest part of the troposphere is eQuestionual to the pressure of 76 cm Hg column.

Question 4. What is stratopause?
Answer:

Stratopause

The thin layer between the stratosphere and mesosphere where. the change in temperature becomes almost negligible is known as the stratopause.

Question 5. Which part of the atmosphere is the coldest?
Answer: Mesosphere.

Question 6. Which gases are predominantly found in thermo sphere?
Answer: Nitrogen and oxygen.

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Question 7. The temperature gradually decreases at a definite rate as we move upward in the atmosphere from the earth’s surface. What is this phenomenon called?
Answer: Normal lapse rate.

Question 8. What is the temperature at the upper end of the troposphere?
Answer: At the upper end of the troposphere, the temperature ranges between -56°C to -60°C.

Question 9. Give examples of local winds.
Answer: Land breeze and sea breeze.

Question 10. Name the lowest layer of atmosphere.
Answer: Troposphere

Question 11. In which layer of the atmosphere do storms and rain occur?
Answer: Troposphere.

Question 12. The living world of the earth’s crust remains in direct contact with which layer of the atmosphere?
Answer: Troposphere.

Question 13. In which layer of the atmosphere does the strongly moving ‘Jet stream’ flow?
Answer: The ‘Jet Stream’ flows in the tropopause region.

Question 14. Through which layer of the atmosphere can a jet plane fly?
Answer: Jet planes can fly through stratosphere.

Question 15. How does the temperature change with an increase in height of the stratosphere?
Answer: The temperature increases with increase in height in the stratosphere.

Question 16. Name some gaseous components present in stratosphere.
Answer: Nitrogen, oxygen, and ozone.

Question 17. What is the temperature of the mesopause part of the mesosphere?
Answer: -92°C.

Question 18. Aurora Borealis is found in which region of the atmosphere?
Answer: Ionosphere region of thermosphere.

Wbbse Class 10 Physical Science And Environment

Question 19. Mention some components of the mesosphere and thermosphere.
Answer:
Some components of the mesosphere: N_2, O_2,
Some components of thermosphere: of, O ^⊕ NO ^⊕

Causes and Effects of Climate Change

Question 20. Which layer is used for communication with the help of radio waves?
Answer: Ionosphere of thermosphere .

Question 21 Mention the maximum temperature of thermosphere.
Answer: Almost 1200°C.

Question 22. Which layer of the atmosphere is suitable for the installation of artificial satellites?
Answer: Exosphere.

Chapter 1 Environmental Concern Topic A Atmosphere Fill In The Blanks:

Question 1. The _________ is the most dense layer of the atmosphere.
Answer: Troposphere

Question 2. The layer separating troposphere stratosphere is called ____________.
Answer: Tropopause

Question 3. When a meteorite enters the earth’s atmosphere, it burns due to it’s collision with the air of __________ layer.
Answer: The Mesosphere

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Question 4. The lower part of the ___________ ionosphere.
Answer: Thermosphere

Question 5. Due to the presence of excess amount of _________ gas in the stratosphere, the temperature of this region rises with altitude.
Answer: Ozone

Question 6. As the distance from the earth surface increases, the __________ of air decreases.
Answer: Density

Question 7. _______ breeze helps in sailing ships offshore.
Answer: Land

Question 8. The term troposphere was first used by the scientist 
Answer: Teisserenc de Bort.

Question 9. The word troposphere means __________ region.
Answer: Turbulent

Question 10. The temperature of the troposphere ___________ with increases in height.
Answer: Turbulent

Question 11. The air layer above the troposphere is called ____________
Answer: Stratosphere

Question 12. The temperature of stratosphere _______ with increase in height.
Answer: Increases

Question 13. The layer of the atmosphere in which Aurora can be seen is _______
Answer: Thermosphere

Question 14. The effect of charged molecules in the ionosphere of atmosphere results in the formation of _________
Answer: Aurora

Question 15. The water cycle of the earth is controlled by ________
Answer: Troposphere

Chapter 1 Environmental Concern Topic A Atmosphere State Whether True Or False:

Question 1. In troposphere, with increase in height, the pressure decreases.
Answer: True

Question 2. Stratosphere is the most dense layer of the atmosphere.
Answer: False

Question 3. Convection currents are formed in solid, liquid, and gaseous states of matter.
Answer: False

Question 4. Heterosphere starts from a height of 85 km. relative to the surface.
Answer: True

Wbbse Class 10 Physical Science And Environment

Question 5. Air pressure decreases with increase in height in troposphere.
Answer: True

Question 6. Water vapour, clouds, etc. do not exist in troposphere.
Answer: False

Question 7. Due to the presence of dust particles in troposphere, the sky looks blue.
Answer: True

Question 8. Aurora can be seen in ozonosphere.
Answer: False

Question 9. The maximum temperature of thermosphere is around 1200°C.
Answer: True

Question 10 Atmospheric pressure in Darjeeling is greater than that in Kolkata.
Answer: False

Chapter 1 Environmental Concern Topic B Ozone Layer, Greenhouse Effect and Global Warming Synopsis

Ozonosphere: The harmful UV rays of the Sun are absorbed by the ozone layer or ozonosphere present in the stratosphere. In this way, the ozone layer protects living organisms from their harmful effects.

Ozone hole: Increased use of chemicals and technology for the development of civilization has adverse effects on the ozone layer. Due to the constant decomposition of ozone molecules, ozone holes are found to be formed at different parts of the ozone layer.

Compounds responsible for ozone layer depletion: Chlorofluorocarbons (CFCs) and oxides of nitrogen (mainly NO) are mainly responsible for the depletion of the ozone layer.

Greenhouse effect: Gases like CO₂, CH₄, N₂O, CFC, and water vapor traps the retransmitted infrared radiations of higher wavelengths. This helps to keep the earth’s surface warm and thus a favorable environment is created for the survival of living beings. This is called the greenhouse effect.

Global warming: Gradual increase in the average temperature of the earth’s atmosphere . due to several natural phenomena as well as man-made activities is called global warming. Greenhouse effect plays an important role to create global warming.

Causes of global warming: Unlimited use of fossil fuels, emission of harmful gases by industries, and deforestation enhance the amount of several greenhouse gases like CO₂, CH₄, CFC, etc. in the atmosphere. The increased amount of such greenhouse gases is one of the main reasons of global warming.

Chapter 1 Environmental Concern Topic B Ozone Layer, Greenhouse Effect and Global Warming Short And Long Answer Type Questions

Importance of Environmental Awareness

Question 1. What is ozonosphere? Why is this layer so essential for us?
Answer:

Ozonosphere:

Stratosphere contains an ozone gas layer which is extended from 16 km to 30 km with respect to the earth’s surface and the concentration of ozone gas is maximum in this layer. This particular layer is called ozonosphere.

The harmful UV rays of the Sun are absorbed by ozone layer. The ozone layer in the stratosphere prevents the UV rays from reaching the earth’s surface and thus, protects living organisms from its harmful effects. That is why ozonosphere is so essential.

Question 2. What is ozone hole?
Answer:

Ozone hole:

Excessive use of different chemicals and technological devices for the development of human civilization leads to a gradual depletion of the ozone layer. The rate of decomposition of ozone is much higher than the rate of its formation of it. As a result, hole is formed in certain regions of the ozone layer which is known as the ozone hole.

Question 3. Name some man-made chemical substances which are responsible for ozone layer depletion.
Answer: Chlorofluorocarbons (CFCs) and some oxides of nitrogen such as nitric oxide (NO) and nitrogen dioxide NO₂ are mainly responsible for depletion of the ozone layer.

Question 4. What is the unit used to measure concentration of ozonosphere? Define the unit.
Answer: The concentration of ozone layer is measured in Dobson unit. At 0°C temperature and 760 mm of Hg pressure, the density of 0.01 mm thick ozone gas layer is called 1 Dobson Unit (1 DU).

Question 5. Describe the significance of ozone layer on the environment.
Answer:

The significance of ozone layer on the environment:

Ozone layer in stratosphere acts as a protective shield for the earth. If the ozone layer was not present in the stratosphere, the ultraviolet rays would reach the earth surface.

As a result- the overall temperature of the earth surface would increase. The increased temperature would lead to extinction of plants and animals on the earth. direct exposure to ultraviolet rays may cause a number of diseases including skin cancer, premature cataract etc.

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Question 6. How is ozone layer formed?
Answer: UV-C (wavelength: 100-280 nm) along with some UV-B. (wavelength: 280-315 nm) decomposes oxygen molecules present in the stratosphere into atomic oxygen. These oxygen atoms then combine with molecular oxygen to form ozone (O3) molecules. The last step is highly exothermic in nature, i.e., large amount of heat is produced in this step.

\(\mathrm{O}_2 \stackrel{(\text { UV-C or UV-B) }}{\longrightarrow} \mathrm{O}+\mathrm{O}\) \(\mathrm{O}_2+\mathrm{O} \longrightarrow \mathrm{O}_3\)

Question 7. Discuss the natural causes that decompose the ozone present in ozone- sphere. How is the total amount of ozone gas maintained in the ozone layer?
Answer: Dissociation of ozone molecules in the stratosphere occurs simultaneously with its formation. Ultraviolet rays of larger wavelength (UV-A; wavelength: 315-400 nm) decompose ozone molecules into molecular oxygen and atomic oxygen.

\(\mathrm{O}_3 \stackrel{\mathrm{UV}-\mathrm{A}}{\longrightarrow} \mathrm{O}_2+\mathrm{O}\)

In stratosphere, formation of ozone molecules and decomposition of ozone molecules occur simultaneously in a cyclic manner and a dynamic equilibrium is maintained between these two processes. As a result, the amount of ozone gas in the stratosphere remains constant.

Question 8. Ozone gas present in stratosphere is important but presence of ozone gas in to- posphere is harmful-justify the statement.
Answer: The harmful UV rays of the Sun are absorbed by ozone layer present in the stratosphere. Hence, this stratospheric ozone is protecting the earth from UV rays and their harmful effects as a natural umbrella.

On the other hand, ozone gas present in troposphere acts as a greenhouse gas (it contributes about 7-8% to the greenhouse effect). The greenhouse effect plays an important role in the gradual increase of the average temperature of the earth.

Question 9. How is the dynamic equilibrium maintained in the stratosphere during the formation and depletion of the ozone layer?
Answer:
Formation of ozone layer: Oxygen molecules. present in the stratosphere absorbs UV rays and are dissociated to form oxygen atoms.

\(\mathrm{O}_2+\text { UV-rays } \rightarrow \mathrm{O}+\mathrm{O}\)

This atomic oxygen combines with molecular oxygen to form ozone molecules-

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\(\mathrm{O}_2+\mathrm{O} \rightarrow \mathrm{O}_3\)

Depletion of ozone layer: Ozone decomposes to 0.12 Discuss the harmful effects of ozone oxygen molecules by absorbing UV rays.

\(\mathrm{O}_3+\text { UV-ray } \rightarrow \mathrm{O}_2+\mathrm{O} ; \mathrm{O}_3+\mathrm{O} \rightarrow 2 \mathrm{O}_2\)

Formation of ozone molecules and decomposition of ozone molecules-these two opposite processes continue in cycles at the ozone layer and an equilibrium is established. It is for this equilibrium that the amount of ozone gas in the stratosphere remains constant.

Question 10. Discuss the role of chlorofluorocarbons (freons) in the depletion of ozone layer.
Answer:

The role of chlorofluorocarbons (freons) in the depletion of ozone layer:

Chlorofluorocarbons (CFCs) act as catalysts in the depletion of ozone layer in the stratosphere. In presence of ultraviolet rays, CFCs dissociate to form active chlorine atoms (CI).

Active chlorine atom reacts with ozone molecule to form oxygen and chlorine monoxide. Chlorine monoxide further reacts with ozone molecules to form oxygen and active chlorine. This process continues in a cyclic manner. As a result, the density of ozone layer decreases.

\(\mathrm{CFCl}_3 \stackrel{\mathrm{UV} \text {-ray }}{\longrightarrow} \dot{\mathrm{C}} \mathrm{FCl}_2+\dot{\mathrm{C}}\) \(\dot{\mathrm{Cl}}+\mathrm{O}_3 \longrightarrow \dot{\mathrm{C}} \mathrm{OO}+\mathrm{O}_2\) \(\dot{\mathrm{ClO}}+\mathrm{O}_3 \longrightarrow 2 \mathrm{O}_2+\dot{\mathrm{C}}\)

Question 11. How are supersonic jet planes responsible for depletion of ozone layer?
Answer: Supersonic jet planes flying through the stratosphere emits large amount of nitric oxide. Nitric oxide (NO) reacts with ozone to form nitrogen dioxide (NO₂) and oxygen.

On the other hand in stratosphere, ozone molecules are decomposed by the UV rays to produce atomic oxygen, which reacts with NO₂ to produce back NO. Thus, the amount of NO never decreases and causes gradual destruction of ozone molecules. As a result depletion of ozone layer takes place.

\(\mathrm{NO}+\mathrm{O}_3 \longrightarrow \mathrm{NO}_2+\mathrm{O}_2\) \(\mathrm{O}_3 \stackrel{\mathrm{UV}}{\longrightarrow} \mathrm{O}_2+\mathrm{O}\) \(\mathrm{NO}_2+\mathrm{O} \longrightarrow \mathrm{NO}+\mathrm{O}_2\)

Question 12. Discuss the harmful effects of ozone layer depletion.
Answer:

The harmful effects of ozone layer depletion:

1. Ozone layer in the atmosphere absorbs harmful UV rays which would otherwise, reach the earth’s surface. This would cause an increase in the earth’s temperature resulting in melting of snow-caps in polar regions. Thus the water level of the seas and oceans would increase and flood the coastal regions.

Exposure to UV rays may cause skin cancer and premature cataract in the eye, and natural immunity also decreases. These rays are
responsible for formation of photochemical Ozone layer in the atmosphere absorbs. harmful UV rays which would otherwise, reach the earth’s surface.

This would cause an increase in the earth’s temperature resulting in the melting of snow-caps in polar regions. Thus the water level of the seas and oceans would increase and flood the coastal regions.

2 Exposure to UV rays may cause skin cancer and premature cataract in the eye, and natural immunity also decreases. These rays are responsible for the formation of photochemical smog.

3 UV rays inhibit the process of photosynthesis in plants, hence production of crop gets reduced.

Question 13. What are greenhouse gases?
Answer:

Greenhouse gases:

Some gases present in the atmosphere absorb radiations of comparatively greater wavelengths (re-radiated from the earth surface) and reflects back the remaining radiations, thus they keep the earth’s atmosphere warm. These gases are known as greenhouse gases.

Some examples of greenhouse gases are carbon dioxide (CO₂), methane ( CH₄), chlorofluorocarbon (CFC), ozone (O₃), nitrous oxide (N₂O), water vapor etc.

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Question 14. What is greenhouse effect?
Answer:

Greenhouse effect:

Infrared (IR) light coming from the Sun accounts for the heating of earth. As it has a smaller wavelength the gases present in the atmosphere are unable to absorb this incident radiation. The IR light re-radiated from the earth surface is of longer wavelengths.

Greenhouse gases like CO₂, CH₄, CFC, N₂O, O₃ etc. absorb these re-radiated wavelengths and thus prevent the heat of the Sun to escape from the earth’s atmosphere. As a result the earth’s atmosphere stays warm and thus a favourable environment is created for the survival of living beings. This phenomenon is known as greenhouse effect.

Question 15. Discuss the importance of greenhouse effect.
Answer:

The importance of greenhouse effect:

Greenhouse gases prevent the reflected radiations to escape from the earth. As a result, the earth’s atmosphere stays warm and thus a suitable environment is created for the survival of living beigns.

If there were no greenhouse gases in the atmosphere, there would have been no greenhouse effect and the earth’s average temperature would fall to -30°C.

Question 16. How do greenhouse gases increase the temperature of the atmosphere?
Answers: IR rays (of shorter wavelengths) of the Sun can easily penetrate the lining of the greenhouse gases (CO₂, CH₄,O₃, N₂O, CFC etc.) present in the atmosphere. The earth’s surface absorbs some part of this radiation and becomes heated. Remaining part of this radiation is retransmitted.

IR rays radiated from the heated earth’s surface is of greater wavelengths and got absorbed by the screen of greenhouse gases. Thus the layer of greenhouse gases maintains the warmth of the atmosphere within a certain range by trapping the retransmitted IR rays. But the amount of greenhouse gases in the atmosphere is gradually increasing due to human activities as well as by natural causes.

As a result greater amount of surface radiated IR rays (of longer wavelengths) getting trapped in the atmosphere which in turn increases the mean [temperature of the earth. Thus greenhouse effect influences rather accelerates the phenomenon of global warming.

Common Environmental Problems and Solutions

Question 17. Name the sources of CO₂ in atmosphere. Discuss its role in creating greenhouse effect.
Answers:
Sources of CO₂ in the atmosphere:
1. Large quantities of CO₂ is added to the atmosphere due to uncontrolled use of fossil fuels in automobiles and factories.
2. In different industries, mainly in case of cement production, a large amount of CO₂ is produced.
3. Cutting down of trees in indiscriminate manner results in the rise of the amount of CO₂ in atmosphere.

Role of CO₂ in creating greenhouse effect:
Amount of CO₂ in atmosphere is maximum, so it has the highest contribution in creating greenhouse effect. Its contribution in greenhouse effect is more than 50%.

Wbbse Class 10 Physical Science Solutions

Question 18. Name the sources of methane gas. Discuss the role of methane gas in greenhouse effect.
Answer:
Sources of methane gas:
1. Methane gas is produced in wetlands due to anaerobic decomposition of dead plants and animals by the action of methanogenic bacteria (methanococcus, methanobacterium).
2. Methane gas is found in oil mines.
3. Decomposition of several organic wastes and the excreta of different animals release methane to the atmosphere

Role In greenhouse effect: The capability of a molecule of methane to trap the re-radiated heat energy is 25 times greater than that of a molecule of CO₂. But the amount of methane in the atmosphere is much lower than that of carbon dioxide. Hence the contribution of methane in greenhouse effect is lower than that of CO₂ which is nearly around 19-20%.

Question 19. What are the sources of chlorofluorocarbons? Discuss their role in causing greenhouse effect?
Answer:
Sources of chlorofluorocarbons: Chlorofluorocarbons are extensively used in refrigerator as refrigerant, fire extinguishers,
1. Aerosol sprays as propellant,
2. Foam and plastic productions etc. Chlorofluorocarbons from these sources are added to the atmosphere.

Role of CFCs in creating greenhouse effect: The capacity of a CFC molecule to trap the retransmitted heat energy is 15000-20000 times greater than that of a CO₂ molecule. These compounds are highly stable and remain in the atmosphere for a long period of time. Contribution of CFCs towards greenhouse effect is nearly around 16%.

Question 20. Discuss the consequences of greenhouse effect.
Answer:

Detrimental consequences of greenhouse effects are

1. Average temperature of earth’s surface and troposphere is constantly increasing which may result in melting of polar ice and snow caps of mountains. Water level of the seas and oceans would thus increase and flood the coastal regions. Saline water will make agricultural land infertile and crop production will significantly decrease.
2. Frequent drought will take place in the countries of northern hemisphere.
3. Frequency and intensity of super cyclones and tornadoes will increase.
4. Living organisms will gradually become extinct due to the intense heat. This will destroy the ecosystem.

Question 21. State some precautionary measures that should be taken to stop global warming.
Answer:
1. Use of fossil fuels has to be controlled.
2. Deforestation should be stopped immediately.
3. Use of non-conventional energy should chlorofluorocarbon carbons have to be banned.
4. Nitrogenous fertilizers should be used in a controlled manner. This will reduce the possibility of mixing nitrogenous oxides in air.
5. Awareness of common people regarding greenhouse effect and global warming will surely reduce the extent of global warming.

Wbbse Class 10 Physical Science Solutions

Question 22. Mention the name of an organic and an inorganic greenhouse gas and their percentage contributions towards global warming.
Answer: An organic greenhouse gas is methane (CH₄) and an inorganic greenhouse gas is carbon dioxide CO₂. The contributions of methane and carbon dioxide towards global warming are 19% and 50% respectively.

Question 23. Why are O₂ and N₂ not considered as greenhouse gases?
Answer: Gases that can absorb infrared radiations of longer wavelengths emitted from the earth’s surface are called greenhouse gases. O₂ and N₂ gases are unable to absorb these retransmitted IR radiations of longer wavelengths, so they do not cause the greenhouse effect. That is why they are not considered as greenhouse gases.

Question 24. What is global warming?
Answer:

Global warming:

Global warming is defined as the gradual increase in the average temperature of the earth’s atmosphere mainly due to the greenhouse effect caused by the uncontrolled increase of several greenhouse gases ( CH₄, CO₂, CFC, etc.) in the atmosphere.

Question 25. Why will the crop production be disrupted as a result of global warming? Or, Mention a detrimental effect of global warming.
Answer: Average temperature of the earth’s atmosphere is gradually increasing which may result in melting of polar ice and the snow caps of mountains. Water level of the seas and oceans would thus increase and flood the coastal regions. The saline water of seas will thus make the fertile agricultural lands unsuitable for cultivation. As a result, crop production will be severely disrupted.

Chapter 1 Environmental Concern Topic B Ozone Layer, Greenhouse Effect and Global Warming Choose The Correct Answer:

Question 1. The coldest region of the atmosphere is
1. Tropopause
2. Mesopause
3. Stratopause
4. Thermopause

Answer: 3. Stratopause

Question 2. Heat reaches the earth surface from the Sun by
1. Conduction
2. Convection
3. Radiation
4. All of these

Answer: 3. Radiation

Question 3. The depletion of ozone layer over the Antarctic region is maximum in the month of
1. March-August
2. September-November
3. January-March
4. April-June

Answer: 3. January-March

Question 4. Oxides of which element is responsible for the decomposition of ozone molecules?
1. Carbon
2. Nitrogen
3. Hydrogen
4. Sulfur

Answer: 2. Nitrogen

Question 5. CFC dissociates in the presence of ultraviolet rays to produce
1. Active carbon atoms
2. Active chlorine atoms
3. Active fluorine atoms
4. Active hydrogen atoms

Answer: 2. Active chlorine atoms

Wbbse Class 10 Physical Science Solutions

Question 6. Which oxide of nitrogen emitted from the supersonic jet planes causes depletion of ozone layer?
1. NO₂
2. N₂O
3. NO
4. N₂O₄

Answer: 3. NO

Question 7. The concentration of ozone in ozonosphere Stain is around
1. 30 ppm
2. 10 ppm
3. 40 ppm
4. 20 ppm

Answer: 2. 10 ppm

Question 8. Which of the following is a greenhouse gas?
1. O₂
2. N₂
3. O₃
4. H₂

Answer: 3. O₃

Question 9. Which of the following is not a greenhouse Jotolygas?
1. CO₂
2. NO₂
3. CH₄
4. N₂O

Answer: 2. NO₂

Question 10. The contribution of the CO₂ Greenhouse effect is almost
1. 30%
2. 20%
3. 50%
4. 60%

Answer: 3. 50%

Wbbse Class 10 Physical Science Solutions

Question 11. Naturally, ozone gas is produced due to the reaction between
1. CFC and O₂
2. UV rays and O₂
3. IR rays with O2ollatay
4. O₂ and water vapor

Answer: 2. UV rays and O₂

Question 12. The correct order of contribution of the given gases towards greenhouse effect is
1. CO₂>CH₄>CFC>O₃
2. CFC>O₃>CH₄>CO₂
3. O₃>CH₄> CFO>CO₂
4. CH₄>CO₂>O₃>CFC

Answer: 1. CO₂>CH₄>CFC>O₃

Question 13. Which would inhibit photosynthesis if it reaches the earth’s surface?
1. Infrared radiation
2. Ultraviolet radiation
3. Radio radiation
4. None of these

Answer: 2. Ultraviolet radiation

Question 14. Source of CFC is
1. A refrigerator
2. Vehicles
3. Agricultural fields
4. Water-bodies

Answer: 1. A refrigerator

Question 15. Which of the following greenhouse gas has the maximum contribution in increasing the temperature of the earth?
1. N₂O
2. CO₂
3. CH₄
4. H₂O vapour

Answer: 3. CH₄

Wbbse Class 10 Physical Science Solutions

Question 16. Dissociation of ozone molecules is done by
1. CI radical
2. OH radical
3. I radical
4. CH₃ radical

Answer: 1. CI radical

Question 17. Which of the following is required to form ozone layer?
1. Ultraviolet ray
2. Visible light
3. Microwave
4. Radiated heatwave

Answer: 1. Ultraviolet ray

Question 18. The ozone layer of the atmosphere absorbs y-Raya-ray UV-ray B-ray 19 The main greenhouse gas is
1. γ-ray
2. α-ray
3. UV-ray
4. β-ray

Answer: 3. UV-ray

Question 19. The main greenhouse gas is
1. CH₄
2. CO₂
3. CFC
4. NO₂

Answer: 2. CO₂

Question 20. Which one of the following plays the key role in depletion of ozone layer?
1. NO₂
2. O₂
3. NO
4. CFC

Answer: 4. CFC

Question 21. Mars gas formed in water-bodies is
1. CO₂
2. CO
3. CH₄
4. C₂H₂

Answer: 3. UV-ray

Wbbse Class 10 Physical Science Solutions

Question 22. Which of the following is responsible for greenhouse effect?
1. γ-ray
2. UV-ray
3. IR-ray
4. X-ray

Answer: 3. IR-ray

Question 23. The full name of CFC is
1. Chlorofluorocarbon
2. Cold fluorinated carbon
3. Carbonfluro chloride
4. Chlorofluoro carbonate

Answer: 1. Chlorofluorocarbon

Question 24. Which of the following does not deplete the ozone layer?
1. NO
2. N₂O
3. CO₂
4. DCFC

Answer: 3. CO₂

Question 25. The ozone layer is formed in the atmosphere due to
1. Chemical reactions
2. Photochemical reactions
3. Nuclear reactions
4. Electrochemical reactions

Answer: 2. Photochemical reactions

Chapter 1 Environmental Concern Topic B Ozone Layer, Greenhouse Effect and Global Warming Answer In Brief

Question 1. Give an example of a gas which is responsible for the gradual increase of atmospheric temperature.
Answer: Carbon dioxide.

Question 2. What percentage of ozone gas found in the atmosphere is present in ozonosphere?
Answer: Ozonosphere contains almost 90% of total ozone gas present in the atmosphere.

Question 3. What happens when ozone molecules absorb ultraviolet rays?
Answer: They decompose to form oxygen molecules.

Question 4. How are UV rays harmful to the eyes?
Answer: Ultraviolet (UV) rays damage the retina of the eyes and may cause premature cataracts.

Question 5. Which instrument is used to measure the density of the ozone gas in atmosphere?
Answer: Dobson spectrometer.

Question 6. How many ozone molecules can be destroyed by an active chlorine atom?
Answer: Over 100,000 ozone molecules.

Question 7. What would be the average temperature of the earth if the greenhouse gases were not present in atmosphere?
Answer: In absence of the greenhouse gases, the average temperature of the earth would have been -30°C.

Question 8. What is the average temperature of the atmosphere due to the presence of greenhouse gases?
Answer: Due to the presence of greenhouse gases, the average temperature of the atmosphere is maintained around 15°C.

Question 9. Which diseases may flourish due to global warming?
Answer: Diseases like dengue, malaria, encephalitis may flourish due to global warming.

Question 10. What do you mean by global warming?
Answer:

Global warming

The phenomenon of gradual increase of earth’s temperature due to greenhouse effect is known as global warming.

Wbbse Class 10 Physical Science Solutions

Question 11. What is the ‘natural sunscreen’ or ‘natural solar screen’ or the ‘umbrella of the earth’?
Answer: The ozonosphere of the stratosphere.

Question 12. Incidence of which ray from the Sun is prevented by the ozone layer?
Answer: UV-ray.

Question 13. Which layer absorbs the Sun’s ultraviolet rays?
Answer: Ozone layer present in the stratosphere.

Question 14. Write down the full form of ODS.
Answer: Ozone Depleting Substances.

Question 15. What is ‘Chapman Cycle’?
Answer:

‘Chapman Cycle’

The cycle of creation and destruction of ozone in the stratosphere is called the Chapman Cycle.

Question 16. What is the full form of ODP?
Answer:

Full form of ODP

Ozone Depletion Potential.

Question 17. Which atom of CFC is responsible for the destruction of the ozone layer?
Answer: The cl atom of CFC is responsible for this.

Question 18. Which gas breaks down the ozone layer during lightning?
Answer: Nitric oxide (NO) gas.

Question 19. What is the role of NO in the depletion of ozone layer?
Answer: NO reacts with O₃ to form NO₂ and O₂ and thus decomposes O_3. As a consequence depletion of ozone layer occurs.
NO + O₃→ NO₂+O₂+hγ

Question 20. In which year was the Montreal Protocol signed?
Answer: Montreal Protocol was signed in 1987.

Question 21. Write the name of an organic greenhouse gas.
Answer: Methane (CH₄).

Question 22. Which is the main greenhouse gas?
Answer: Carbon dioxide (CO₂).

Question 23. Write the full form of GWP.
Answer: Global Warming Potential.

Question 24. Mention a detrimental effect of global warming.
Answer: As global warming increases, polar ice caps will melt and as a result, coastal areas will be flooded.

Chapter 1 Environmental Concern Topic B Ozone Layer, Greenhouse Effect and Global Warming Fill In The Blanks

Question 1. Ozonosphere is present in the  _______.
Answer: Stratosphere

Question 2. ________ was the first to observe the formation of holes in the ozone layer.
Answer: Joe Farman

Question 3. The full form of CFC is a ___________
Answer: Chloroflurocarbon

Question 4. Ozone is a gas with pale blue, _________ Color and a smell.
Answer: Pungent

Question 5. Ozone gas is an allotrope of _______ gas.
Answer: Oxygen

Question 6. The density of ozone gas in atmosphere is measured in the_______ unit.
Answer: Dobson

Question 7. Nitrous oxide and water vapor are _______ gases.
Answer: Greenhouse

Question 8. _______ layer of the atmosphere is also known as the ‘earth’s protective umbrella’.
Answer: Ozone

Question 9. The capacity of a molecule of methane to retain the absorbed heat energy is ______ times more than that of a CO₂ molecule.
Answer: 25

Question 10. The wavelength of infrared radiation______ with decreasing energy.
Answer: Increases

Question 11. The rate of increase of CFC gas in the atmosphere per year is ______
Answer: 5%

Question 12. The gas emitted by supersonic aircraft breaks down the ozone layer is _______
Answer: Nitric Oxide

Question 13. The destruction of the ozone layer can cause diseases like ________
Answer: Skin cancer

Question 14. An inorganic greenhouse gas is _________
Answer: Carbon dioxide

Question 15. The _____________ present in the body spray is a greenhouse gas.
Answer: Chloroflurocarbon

Question 16. The greenhouse effect is causing ____________
Answer: Global Warming

Chapter 1 Environmental Concern Topic B Ozone Layer, Greenhouse Effect and Global Warming State Whether True Or False:

Question 1. Nitrogen is a greenhouse gas.
Answer: True

Question 2. Supersonic jets release huge amount of nitric oxide.
Answer: False

Question 3. Scientist Joe Farman first noticed the formation of the ozone hole over Antarctica.
Answer: False

Question 4. Under the influence of UV rays, CFC splits and produces methane gas.
Answer: True

Question 5. The Montreal Protocol was signed in the year 1987.
Answer: False

Question 6. Damage to the ozone layer will increase the chance of cataracts.
Answer: False

Question 7. It would have been easier for the fauna to survive if there were no greenhouse gases in the atmosphere.
Answer: True

Question 8. The two gases responsible for the greenhouse effect are nitrogen and oxygen.
Answer: True

Question 9. Among all greenhouse gases the contribution of carbon dioxide is maximum in creating greenhouse effect.
Answer: False

Question 10. If there were no greenhouse gases, the temperature of the earth would be 50°C.
Answer: True

Chapter 1 Environmental Concern Topic C Proper Uses of Energy and Sustainable Development Synopsis

Calorific value: Heat energy produced due to the complete combustion of 1 kg of a fuel is known as its calorific value. Unit: kJ • kg-1 (in SI).

The necessity of conservation of fossil fuels:
The incessant use of fossil fuels (coal, petroleum, natural gas) is gradually depleting the reserve of these fuels. To conserve these fuels, we must encourage the use of alternative fuels which are basically non- conventional renewable energy sources.

Alternative fuels: Alternative fuels are those which are being used to restrict the use of fossil fuels in order to conserve their sources as these are gradually running out. Examples: Solar energy, wind energy, tidal energy etc.

Sustainable development: Controlled and systematic use of natural resources to meet the need of present generation as well as sustaining them for future generation is called sustainable development. First step of sustainable development is to encourage the use of alternative sources of energy that are renewable and eco-friendly.

Purposes of sustainable development: Social welfare, Economic development and Ecological development are the major three purposes of sustainable development.

Conventional/non-renewable sources of energy: These sources are gradually exhausting due to their prolonged uses and these sources cannot be renewed.
Examples: Coal, petroleum, natural gases etc.

Non-conventional/renewable sources of energy: These sources have presently been used as alternative energy sources and these are inexhaustible and renewable.

Examples: Solar energy, wind energy, biomass energy, tidal energy etc.

Chapter 1 Environmental Concern Topic C Proper Uses of Energy and Sustainable Development Short And Long Answer Type Questions:

Question 1. What is sustainable development?
Answer:

Sustainable development:

The controlled and systematic use of natural resources to meet the need of present generation as well as sustaining resources for the future generation is called sustainable development.

Question 2. Discuss the purposes of development’.
Answer:
Purposes of sustainable development are Social welfare:
Major goal of sustainable development is to establish social equality and eradicate the differences that arise from social misconceptions, superstitions, backward traditions etc.

Economic development: No society can prosper without economic development. It is required in the field of education, health, agriculture and industries. Hence, one of the major goals of sustainable development is to achieve economic development.

Ecological development: Ecology of earth depends on the constant interaction between living and non-living things. Sustainable development also aims at maintaining proper balance in nature and building a stronger relationship between living & non-living world. of ‘sustainable

Role of Government in Environmental Protection

Question 3. Why is sustainable development considered to be of utmost importance for the present as well as a future generations?
Answer: The aim of sustainable development is to use natural resources without affecting the environment. This will enable both present and future generations to preserve natural resources and utilize them for a long time.

It gives importance not only to economic development but also to cultural, social & geopolitical development have been able to control the decline of environmental conditions as it encourages to decrease the use of conventional sources of energy and increases the use of alternative resources.

Question 4. What are fossil fuels?
Answer:

Fossil fuels:

Fossil fuels are natural fuels formed due to the action of geothermal heat, pressure, and bacterial degradation of the dead plants and animals buried beneath the earth’s crust for many years. Coal, petroleum, natural gas are examples of fossit fuels. These are exhaustible and non¬ renewable sources of energy.

Question 5. What do you mean by conventional or non-renewable sources of energy? Give examples.
Answer:

The sources of energy which- are gradually exhausting due to their prolonged uses and which cannot be renewed are called conventional or non-renewable sources of energy.

These have been used as the major energy source till date and hence their reserves are gradually running out. Coal, petroleum, natural gases are examples of conventional or non-renewable sources of energy.

Question 6. What are non-conventional? orrenewable sources of energy? Give examples.
Answer:

The sources of energy that have presently been used as alternative energy sources to minimize the uses of fossil fuels and which are in exhaustible and renewable are known as non-conventional or renewable sources of energy. Solar energy, wind energy, biomass energy, tidal energy, etc. are examples of non-conventional or renewable sources of energy.

Question 7. Write three differences between conventional and non-conventional sources of energy.
Answer:

The major differences are listed below:

Conventional sources of energy	Non-conventional sources of energy
1. These sources of energy are extensively used and their reserves are gradually exhausting. Examples—are coal,    petroleum, natural gas, etc.	1. These sources of energy are not being used extensively. These sources are exhaustible and they are mostly reusable in nature. Example-wind energy, are solar energy, tidal energy, etc.
2. These sources of energy cause pollution.	2. These sources are non-polluting in nature.
3. The sources of energy are not evenly distributed throughout the world.	3. Non-conventional energy sources are almost evenly distributed.

Question 8. Why should fossil fuels?
Answer:

The natural reserves of fossil fuels are gradually running out. The sources of such fuels are abruptly exhausting due to their indiscriminate usage. As a result, the world may face a severe energy crisis and development of human civilization may cease in near future.

These sources of energy are non-renewable. Combustion of fossil fuels produces several greenhouse gases. Hence controlled use of these fuels will minimize the chances of global warming.

Question 9. How is electricity generated from wind energy?
Answer:

Practically, the kinetic energy of the wind is harnessed to obtain wind energy. Using windmills, wind energy can be converted into electrical energy.

The blades of the windmills are connected to the turbines of an electrical generator. When the blades rotate by the action of wind, the turbines also rotate and electricity is generated.

Question 10. How is electricity generated using tidal energy?
Answer:

During high tides, the surging water is stored in a dam and during the low tides this stored water is released, which comes down with a high velocity.

Turbines of electrical generators are placed in the path of moving water and thereby the kinetic energy of water can be converted into electrical energy.

Question 11. How is electricity generated using geothermal energy?
Answer:

During volcanic eruptions, most of the magma coming out from the earth, gets stuck in the rocks near the earth surface at a depth of 5 to 10 km. These rocks, in contact with the magma, gets heated up.

When water passes through these hot rocks, it vaporizes to form steam. The steam is piped out directly from the underground wells to the power plants. The kinetic energy of the steam rotates the turbines and generates electricity.

Question 12. What are methanogenic bacteria? Give examples.
Answer:

Methanogenic bacteria

Methanogenic bacteria can be defined as microorganisms that produce methane gas by the anaerobic decomposition of biomass. Some examples of methanogenic bacteria are Methanococcus, Methanobacterium etc.

Question 13. Discuss the role of methanogenic bacteria in increasing the amount of methane in the atmosphere.
Answer:

Methanogenic bacteria decompose dead plants in wetlands, rain forests etc. to produce methane gas. Thus, the amount of methane in atmosphere increases.

Question 14. What is biomass energy? What are the disadvantages of using biomass energy?
Answer:

Biomass energy:

Biomass refers to dead plants and plant remains, domestic wastes, agricultural wastes, animal excreta, animal carcasses etc. Energy stored in biomass is known as biomass energy.

Biomass energy is considered to be one of the major alternative sources of energy to replace fossil fuels. However, it has some harmful effects on environment as the combustion of biomass causes air pollution.

Question 15. What is biogas? What are its constituents?
Answer:

Biogas:

Biomass refers to dead plants and plant remains, domestic wastes, agricultural wastes, animal excreta, animal carcasses, etc. The biomass is enclosed in a large chamber and decomposed by the action of methanogenic bacteria to produce a combustible gas, known as biogas.

The major components of biogas is methane (CH₄). Apart from methane, carbon dioxide CO_2, and traces of H₂, N₂, CO, O_2, H₂S, and water vapor are also present in it.

Question 16. Write some uses of biogas.
Answer:

Some uses of biogas:

Biogas can be used as a fuel to light lamps, to heat water, and for cooking purposes. In many countries, it is used to dry bricks, ceramic tiles, tobacco etc. Electricity generated from biogas can be used to run small pumps and small-scale industries.

Question 17. What is biofuel? Give examples.
Answer:

Biofuel:

The fuel produced from biomass is known as biofuel. Bioethanol produced by fermentation of corn or sugar cane is an example of biofuel. It is mixed with petrol and used as automobile fuel.

Question 18. What is methane hydrate?
Answer:

Methane hydrate:

Methane hydrate is a crystalline solid substance (clathrate compound) in which a large amount of methane molecules are trapped inside the cage-like lattice of ice. It is represented by the formula 4CH₄ 23H₂O. It exists only under suitable temperatures and pressure.

Question 19. How is methane present in coal mines?
Answer: Due to bacterial action or geothermal heating, methane gas is produced in coal seams. The coal seams are saturated by ground water and the produced water pressure causes methane gas to get absored in the coal seam.

Question 20. Why is methane gas extracted before the mining of coal?
Answer: Before the mining of coal, methane gas should be extracted as much as possible from the coal bed. This is because- it will reduce the probability of catching fire and chances of accidents can be averted, the extracted methane gas can be used as a potential fuel.

Question 21. Why is methane hydrate considered as an important source of energy?
Answer: Recent discovery of methane hydrate explores a new dimension of energy resources. Scientists have estimated that methane hydrate contains more carbon than all the fossil fuel available on the earth, combined together.

1 Litre of methane hydrate is found to contain 170 Litre of methane gas in STP. When the world is facing an energy crisis due to exhaustion of fossil fuels, methane hydrate provides a complete new direction towards energy resources.

Question 22. State the concerns of using methane?
Answer:

Concerns of using methane

Methane hydrate is not as stable as other minerals. Due to increase in temperature or decrease in pressure, it may be transformed into water and methane gas may be released from the mineral. This may cause landslide beneath the earth surface. Methane is a major greenhouse gas. Heating methane hydrate may release methane gas to the atmosphere which may lead to global warming.

Question 23. Discuss some advantages of using solar energy.
Answer:

Some advantages of using solar energy:

Solar energy is inexhaustible and renewable. Scientists consider it as the most important source of alternative energy. Unlike fossil fuels, solar energy does not cause pollution. source of energy is very effective in less populated areas and in those regions where the .conventional sources of energy are not widely available. The production of solar energy requires minimum natural resources.

Question 24. Mention some disadvantages of using solar energy.
Answer:

Some disadvantages of using solar energy:

Production cost of solar energy is very high as it requires complex technological support. So, under-developed countries find this energy unsuitable for use.

The initial cost of installing solar panels is very high. This is one of the major disadvantages of solar energy. Areas which do not get sufficient sunlight, are not suitable for utilising solar energy. Solar energy centers produce solar energy in limited quantities which can satisfy only the local need.

Question 25. Mention some advantages of wind energy.
Answer:

Some advantages of wind energy:

Wind energy is renewable and is source is inexhaustible. Even it’s incessant use will not create energy crisis. Even though initial cost of installation is somewhat high, regular cost is very create energy crisis. Recurring cost is very low. This energy source does not cause pollution.

Question 26. Mention some advantages of tidal energy.
Answer:

Some advantages of tidal energy:

Tidal energy is renewable and is source is inexhaustible. Even it’s incessant use will not create energy crisis. Recurring cost is very slow. This energy sorce does not cause pollution.

Question 27. Discuss some advantages of geothermal energy.
Answer:

Some advantages of geothermal energy:

1. This source of energy is inexhaustible.
2. Being inexhaustible, it can be supplied continuously throughout the day.
3. Direct use of this energy inhibits the release of greenhouse gases into the atmosphere, thereby preventing pollution.

Question 28. Mention some advantages of biomass energy.
Answer:

Some advantages of biomass energy:

Biomass energy is a renewable source of energy. The residue left after production of biogas from biomass can be used as fertilizers.

Biogas can be used as fuels and for the generation of electricity. Pollution caused by the waste material during biomass production can be controlled by using them for production of biogas.

Question 29. How is electricity produced from domestic wastes?
Answer: Initially, substances that can be recycled are separated from the domestic wastes. Remaining wastes are then placed into a furnace through a hopper. These are then burnt in the combustion chamber. The heat so produced vapourises the water taken in a tank above the furnace.
The vapour is used to rotate the turbine which in turn generates electricity.

Question 30. Mention some uses of coalbed methane (CBM).
Answer:

Some uses of coalbed methane (CBM)

Coalbed methane (CBM) can be used as a fuel for domestic as well as industrial purposes. It can be used as a substitute of natural gas in power stations. It can be liquefied by applying pressure. The liquefied gas can be used in automobiles.

Question 31. Classify biofuel. Give example of each Characteristics of each type?
Answer:

Biofuel:

The fuel produced from biomass is called biofuel. It is classified into three groups- solid biofuel, liquid biofuel and gaseous biofuel. Solid biofuel: Wood, straw, domestic wastes etc., are examples of solid biofuels.

Liquid biofuel: Bioethanol (produced by fermentation of corn or sugarcane), biodiesel (produced by transesterification of oil or fat) are examples of liquid biofuels.

Gaseous biofuel: Biogas or gobar gas is an example of gaseous biofuel.

Question 32. How is methane gas extracted from coal mines?
Answer: A vertical hole is drilled through the ground into coal seam. Coal seam remains saturated in When the water is pumped out, the pressure over the coal seam decreases and methane gas is released from the coal seam. The gas then comes out through the hole and its collected and supplied through pipelines.

Question 33. What is ignition point of a fuel? What are the characteristics of a good fuel?
Answer:

The ignition point of a fuel can be defined as the lowest temperature at which the fuel catches fire and undergoes combustion.

Characterisitics of a good fuel:

1. It should possess a high calorific value.
2. It should have a proper ignition temperature. The ignition temperature of the fuel should neither be too low or too high.
3. It should not produce poisonous products during combustion. In other words, it should not cause pollution during the time of combustion.
4. It should have a moderate rate of combustion. Combustion should easily be controlled i.e.
5. It should be easier to start or stop the combustion of the fuel when required. Combustion of the fuel should not produce. much ash.
6. It should be cheap and well available. The transportation and handling of the fuel must be easier.

Question 34. What do you mean by calorific value of fuel? Which one of coal and diesel has higher calorific value?
Answer:

Calorific value of fuel

The amount of heat produced due to the complete combustion of 1 kg of a fuel is known as its calorific value. Its value is represented in It is actually a metal box with a heat-insulating kl. kg^-1 unit in Sl.

The calorific value, of diesel (44800 kJ. kg^-1) is greater than that of coal (15000-34000 kJ.kg^-1).

Question 35. What are the uses of solar energy?
Answer:

Solar energy is a renewable, inexhaustible, and affordable form of energy.

It can be used in following ways-

1. Solar electricity can be generated through solar panels and is used to light streets, houses, health centres etc.
2. Solar water heaters are used to heat water by Solar water heater is used to heat water using using solar energy.
3. Solar space heating systems include radiant floors or a Force Hot Air (FHA) system to heat a home thus reduces the overall electricity cost.
4. Solar ventilation solution such as solar attic fans can reduce the burden of HVAC by helping to cool the home during summer.
5. Solar cookers can be used for cooking purposes.
6. Solar powered vehicles (e.g. buses, small cars etc.) are used in many cities.

Question 36. Mention the uses of solar cells.
Answer:

In a solar cell, solar energy is converted into electrical energy and the generated electricity can be stored in batteries or can be used directly.

1. Water can be pumped up with the help of this energy.
2. Motor cars can be driven by installing solar panels.
3. This energy can be used in artificial satellites, space ships or space stations.
4. Radio stations and TV relay stations can use this energy.
5. This energy can be used to supply powers to traffic signals, solar calculators etc.

Question 37. Briefly discuss about solar cooker.
Answer:

The properties of solar cooker are:

1. Solar cooker is a cheap, energy-saving, pollution-free tool used in cooking. the environment i.e. it is completely pollution free.
2. It is actually a mental box with a heat-insulting coating around it.
3. Black color is avery good heat absorber, so the inner surfaces are painted black.
4. With the help of a reflector, the sunlight is concentrated and applied to the box to create high temperature.
5. The surface of the cooker is covered with a glass plate to increase the temperature inside

Question 38. Briefly discuss about solar water heater.
Answer:

The properties of water heater are:

1. Solar water heater is used to heat water using solar energy.
2. A black-painted metal box and a black- painted copper coil are placed inside it.
3. Sun rays are being reflected into the box with the help of a reflector to create a high temperature, which also heats the inner copper coil.
4. The water flowing through the hot copper coil is also heated in this way.

Question 39. Mention a few uses of wind energy.
Answer:

Few uses of wind energy are:

1. Wind power is used to generate electricity by winding the wind turbines.
2. With the help of windmill it is possible to grind different grains or spices, pump water etc.

Question 40. Mention the advantages and disadvantage of using geothermal energy.
Answer:

Advantages of using geothermal energy:

1. The supply of geothermal energy is inexhaustible, i.e., its stock will never run out despite being used repeatedly.
2. Using of geothermal energy causes no harm to the environment i.e. it is completely pollution free.

Disadvantages of using geothermal energy:

1. The construction of geothermal power generation plants is extremely expensive.
2. Due to the use of advanced technology, the cost per unit of this power generation is higher than that of conventional power plant.

Question 41. Write the differences between conventional and non-conventional sources of energy.
Answer:

Differences between conventional and non-conventional sources of energy:

Conventional sources  of energy	Non-conventional Sources of energy
1. Conventional sources of energy (e.g. coal, petroleum, and natural gas) are nonrenewable sources of energy and that is why there is a probability of that such sources might be exhausted by excessive use.	1. Non-conventional sources of energy (e.g. solar energy, wind energy) are renewable sources of energy and thus they can not be exhausted.
Z- These energy sources have been used for a long time. For. example, the use of coal and petrol has been around for a . long time.	2. The use of these energy sources (e.g., solar energy, wind energy, tidal energy) is not very common. Their use has recently become popular.
3. Use of these energy sources causes environmental pollution.	3. Use of these energy sources does not cause environmental pollution at all.
4. The use of these energy sources is not conducive to sustainable development.	4. The use of these energy sources is conducive to sustainable development.
5. A variety of byproducts can be obtained during the extraction of these energies. For example, naphthalene, coal tar, etc. are obtained during the extraction of coal.	5. No by-products can be obtained during the extraction of these energies.

Question 42. In which type of natural environment is methane hydrate found?
Answer: The topography and environment of some parts of the world are favorable to the formation and sustainability of methane hydrate. Those are:

1. Sedimentary rock layers below the frozen soil layer (Permafrost) of the polar region.
2. The sedimentary layer is present at the bottom of large lakes and the seas in the subcontinental region.
3. The bottom region of frozen ice in the polar region.

Question 43. Why is methane hydrate termed as ‘fiery ice’?
Answer:

Methane hydrate is a solid, crystalline substance having the composition of 4CH₄. 23H₂O. A large amount of methane is trapped in these ice-like crystals. Methane is a combustible substance, hence methane hydrate starts to burn on contact with fire. Only water is left after combustion. That is why methane hydrate is termed as ‘fiery ice’.

Chapter 1 Environmental Concern Topic C Proper Uses of Energy and Sustainable Development Choose The Correct Answer:

Question 1. Which of the following is a fossil fuel?
1. Coal
2. Petroleum
3. Natural gas
4. All of these

Answer: 3. Natural gas

Question 2. Among petrol, diesel, kerosene, and LPG, which one has the highest calorific value?
1. Peterol
2. Kerosene
3. Diesel
4. LPG

Answer: 4. LPG

Question 3. Which of the following represents the correct order of calorific values of the corresponding fuels?
1. Coal < diesel < hydrogen < LPG
2. Coal < hydrogen < diesel < LPG
3. Coal < diesel < LPG < hydrogen
4. Coal < LPG < diesel < hydrogen

Answer: 3. Coal < diesel < LPG < hydrogen

Question 4. Which of the following is a fossil fuel?
1. Coal
2. Petroleum
3. Natura! gas
4. All of these

Answer: 4. All of these

Question 5. Fossil fuels need to be conserved because
1. These are very expensive
2. These are not easily available
3. These are non-renewable
4. None of these

Answer: 3. These are non-renewable

Question 6. Which of the following elements is the major constituent of solar cells?
1. Li
2. Na
3. Si
4. Cu

Answer: 3. Si

Question 7. The major source of energy which meets our daily demands is
1. Solar energy
2. Wind energy
3. Tidal energy
4. Fossil fuels

Answer: 4. Fossil fuels

Question 8. Solar energy gets converted into electrical energy in a/an
1. Photo voltaic cell
2. Solar cooker
3. Pressure cooker
4. Electric motor

Answer: 1. Photo voltaic cell

Question 9. The least polluting fossil fuel is
1. Diesel
2. Coal
3. Kerosene
4. Natural gas

Answer: 4. Natural gas

Question 10. Source of non-renewable energy is
1. Wind energy
2. Petroleum
3. Tidal energy
4. Solar energy

Answer: 2. Petroleum

Question 11. The energy stored in coal, petroleum, etc. is
1. Wind energy
2. Solar energy
3. Tidal energy
4. Renewable energy

Answer: 2. Solar energy

Question 12. Which gas found in coal mines is used as a fuel?
1. Ozone
2. Methane
3. Oxygen
4. Nitrogen

Answer: 2. Methane

Question 13. An example of methanogenic bacteria is
1. Methanococcus
2. Methanobacterium
3. Both 1 and 2
4. None of these

Answer: 3. Both 1 and 2

Question 14. Which of the following does work on the principle of the greenhouse effect?
1. Solar cooker
2. Radio station
3. Windmill
4. Biogas plant

Answer: 1. Solar cooker

Question 15. The largest windmill of India is situated in
1. Kanyakumari (approx. 380MW)
2. Surat (approx. 220MW)
3. Haridwar (approx. 460MW)
4. Sagardwip (approx. 410MW)

Answer: 1. Kanyakumari (approx. 380MW)

Question 16. The state with the largest installed wind power generation capacity in India is
1. Tamil Nadu
2. West Bengal
3. Kerala
4. Maharashtra

Answer: 1. Tamil Nadu

Question 17. Which of the following are eco-friendly fuels
(1)Coal,
(2)Kerosene,
(3)Natural gas,
(4)Biogas

1. (1) and (4)
2. (3) and (4)
3. (1) and (2)
4. (1) and (3)

Answer: 3. (1) and (2)

Question 18. Which type of coal has the highest calorific value?
1. Pit
2. Lignite
3. Anthracite
4. Bituminous

Answer: 3. Anthracite

Question 19. The main component of biofuel is
1. Carbon dioxide
2. Ethanol
3. Methanol
4. Ether

Answer: 2. Ethanol

Question 20. Solar cells are formed by
1. Conductors
2. Insulators
3. Semiconductors
4. Superconductors

Answer: 3. Semiconductors

Question 21. Source of the solar energy is
1. Nuclear fission
2. Coal
3. Nuclear fusion
4. Petroleum

Answer: 3. Nuclear fusion

Question 22. Formula of methane hydrate is
1. CH_3.H20
2. 4CH₃-23H₂O
3. CH₃OH
4. 4CH₄-23H₂O

Answer: 4. 4CH₄-23H₂O

Question 23. Fiery ice is
1. CO₂
2. Methane
3. Methane hydrate
4. Methanol

Answer: 3. Methane hydrate

Question 24. For which ray of sunlight does a solar cooker work?
1. Gamma ray
2. Infrared ray
3. Ultraviolet ray
4. Visible ray

Answer: 3. Methane hydrate

Question 25. What should be the minimum wind velocity for proper operation of a wind-power generator?
1. 15 km/h
2. 25 km/h
3. 35 km/h
4. 45 km/h

Answer: 1. 15 km/h

Question 26. The main component of biogas is
1. CO₂
2. CH₄
3. H₂
4. H₂S

Answer: 2. CH₄

Question 27. Which is not a source of biomass energy?
1. Agricultural waste
2. Cow dung
3. Wood
4. Nuclear fission

Answer: 4. Nuclear fission

Question 28. A source of non-conventional energy is
1. Petrol
2. Kerosene
3. Biogas
4. Coal

Answer: 3. Biogas

Question 29. In which of the following states does methane hydrate exists?
1. Solid
2. Liquid
3. Gas
4. Any physical state

Answer: 1. Solid

Question 30. The potential difference formed in solar cells
1. 0 V
2. 0.5 V
3. 220 V
4. 110 V

Answer: 2. 0.5 V

Chapter 1 Environmental Concern Topic C Proper Uses of Energy and Sustainable Development Answer In Brief

Question 1. What do you mean by alternative fuels?
Answer:

Alternative fuels

Alternative fuels are those which are being used to restrict the use of fossil fuels in order to conserve their sources as these are gradually running out.

Examples: solar energy, wind energy, etc.

Question 2. Mention two major sources of energy.
Answer:

Two major sources of energy

1. Conventional sources of energy and
2. Non-conventional sources of energy.

Question 3. Name a conventional and renewable source of energy.
Answer: Wind power.

Question 4. Write the name of a conventional and nonrenewable source of energy.
Answer: Coal (fossil fuel).

Question 5. Write the names of two non-conventional and renewable sources of energy.
Answer:
1. Solar energy,
2. Tidal energy.

Question 6. Write the names of two non-conventional and non-renewable sources of energy.
1. Geothermal energy,
2. Nuclear energy.

Question 7. Why is the inner surface of a solar heater painted black?
Answer: Black surface can absorb more heat from sunlight. So, the inner surface of a solar heater is painted black.

Question 8. Which fuel has the highest calorific value?
Answer: Hydrogen (150000 kJ/kg) has the highest calorific value.

Question 9. Why do the pipelines of natural gas often get blocked?
Answer: The pipelines of natural gas often get blocked due to the formation of solid methane hydrate.

Word Problems Related to Environmental Issues

Question 10. The gas trapped in coal mines is a potential source of energy. Name the gas. Why is it called firedamp? OR, What is firedamp?
Answer:
1. The gas is methane (CH₄).
2. Methane gas accumulated in coal mines forms an explosive mixture when mixed with air and often causes fire in coal mines. So this gas is named as firedamp.

Question 11. How is electricity produced in solar cells?
Answer: When photons present in sunlight are incident on the surface of the solar cell (made up of semiconductors, such as Si), the electrons get excited and ultimately becomes free. These free electrons generate electricity.

Question 12. What is geothermal energy?
Answer:

Geothermal energy

When groundwater passes over hotbeds of rocks, it gets vaporised. These vapours are utilized to move the plates of a turbine thereby producing electrical energy. This is known as geothermal energy.

Question 13. What is tidal energy?
Answer:

Tidal energy

During tides, the kinetic energy of water can be converted into electrical, energy using turbines. This energy is known as tidal power or tidal energy.

Question 14. Which is the major raw material used for the production of biogas?
Answer: Cow dung.

Question 15. What is the calorific value of fuel?
Answer:

Calorific value of fuel

The amount of heat produced due to the complete combustion of 1 kg of a fuel is known as its calorific value. Its value is represented in kJ • kg-1 unit in SI.

Question 16. How is biodiesel produced?
Answer: Biodiesel is produced due to the transesterification of vegetable oil and animal fats.

Question 17. Which seeds are used to produce biodiesel in India?
Answer: The seeds of the jatropha tree are used to produce biodiesel in India.

Question 18. What is ‘methane hydrate’?
Answer:

‘Methane hydrate’

Methane hydrate is a crystalline solid where methane molecules remain trapped inside a cage-like lattice of ice.

Question 19. Write down the unit of calorific value of a fuel.
Answer: The SI unit of calorific value of a fuel is J/kg and the CGS unit is cal/g.

Question 20. The calorific value of LPG is 50 kJ/g —Explain.
Answer: It means that 50 kJ of heat is obtained by the combustion of 1 g of LPG.

Question 21. Arrange in ascending order of calorific value—Kerosene, Wood, Coal, Hydrogen, LPG, Diesel.
Answer: Wood > Coal > Diesel > Kerosene > LPG > Hydrogen

Question 22. Write the name of fossil fuel.
Answer: Coal.

Question 23. Which gas is filled in the gas cylinder used for cooking?
Answer: Liquefied Petroleum Gas (LPG)

Question 24. What is the main component of LPG?
Answer: Butane.

Question 25. What is the main component of CNG?
Answer: Methane.

Question 26. Which of the following is a fossil fuel? Charcoal, Petrol, Ethanol.
Answer: Petrol

Question 27. Which gas is produced during the combustion of fossil fuels?
Answer: CO₂(Carbon dioxide).

Question 28. Write the name of a conventional renewable pollution-free energy source.
Answer: Wind power.

Question 29. Write the name of an environment-friendly non-conventional energy source.
Answer: Geothermal energy.

Question 30. Write the name of an alternative energy source.
Answer: Solar energy.

Question 31. Write the name of a device that uses solar cells.
Answer: Solar calculator.

Question 32. What is generated from the wind power of wind mill?
Answer: Electrical energy.

Question 33. Write the name of a place in West Bengal that has windmills.
Answer: Fraserganj.

Question 34. Name an energy source that does not come directly or indirectly from the sun.
Answer: Geothermal energy.

Question 35. What is available as residue in the controlled construction of wood?
Answer: Charcoal.

Question 36. Methanogenic Bacteria decompose substances to produce methane gas.
Answer: Biomass.

Question 37. Give an example of Methanogenic Bacteria.
Answer: Methanogens—Methanosarcina barkeri

Question 38. Mention the use of Biogas.
Answer: Biogas can be used as a fuel for cooking purposes.

Question 39. Write down the fuel form of CBM.
Answer: Coalbed methane.

Question 40. What is sweet gas?
Answer:

Sweet gas

Methane gas obtained from coal mines is called sweet gas.

Question 41. What is ‘fiery ice’?
Answer:

‘Fiery ice’

Methane Hydrate ((4CH₄• 23 H₂O ) is called ‘fiery ice’.

Question 42. How much volume of methane gas can be obtained from 1 Litre of methane hydrate at NTP?
Answer: Almost 170 Litre of methane gas can be obtained from 1 Litre of methane hydrate at NTP.

Chapter 1 Environmental Concern Topic C Proper Uses of Energy and Sustainable Development Fill In The Blanks:

Question 1. The calorific value of LPG is _________.
Answer:  55000 kJ/kg.

Question 2. The major component of biogas is ________
Answer: Methane

Question 3. Apart, from methane, another gas that is found in biogas is ________.
Answer: CO₂

Question 4. At STP, about __________ of methane is obtained from 1 L of methane hydrate.
Answer: 170L

Question 5. Methane hydrate is a solid _________ compound.
Answer: Clathrate

Question 6. _________ river basin in India has one of the largest reserves of methane hydrate.
Answer: Krishna-Godavari

Question 7. The idea of sustainable development is properly developed in the report of the __________ Commission.
Answer: Brundtland

Question 8. Biogas is produced due to the anaerobic decomposition of cow dung by __________ bacteria.
Answer: Methanogenic

Question 9. The calorific value of methane is _________ than petrol.
Answer: Less

Question 10. In photovoltaic cells, solar energy is directly converted into _________ energy.
Answer: Electrical

Question 11. In artificial satellites, the main source of energy is the energy produced by __________
Answer: Solar Cells

Question 12. The value of solar constant is approximately ________
Answer:  1.4kW/m²

Question 13. Biogas contains _______ of methane gas.
Answer: 50-80%

Question 14. Among wood and methane, the calorific value is more in case of __________
Answer: Methane

Question 15. The substance used to make solar cell is ________
Answer: Silicon

Question 16. Electrical energy is obtained from in solar cells ___________
Answer: Solar energy

Question 17. _________ is generated from wind power in wind mills.
Answer: Mechanical Energy

Question 18. _________ in West Bengal is a region that is rich in geothermal energy.
Answer:  Barkreshwar

Question 19. Vegetable wastes are decomposed by anaerobic bacteria in __________ of air in the biogas plants.
Answer: Absence

Question 20. To produce biogas___________ bacteria is needed.
Answer: Methanogenic

Question 21. The hard coal in the mine contains a large amount of_______ in the absorbed state.
Answer: Methane

Question 22. _____________ is also termed as fiery ice.
Answer: Methane Hydrate

Question 23.  _________ gas is obtained from methane hydrate.
Answer: Methane

Chapter 1 Environmental Concern Topic C Proper Uses of Energy and Sustainable Development State Whether True Or False:

Question 1. The calorific value of kerosene is greater than LPG.
Answer: False

Question 2. Semiconductors like Si, Ge, etc., are used in solar cells.
Answer: True

Question 3. Gasoline is a kind of biofuel.
Answer: False

Question 4. Methanogenic bacteria play a major role in biogas production.
Answer: True

Question 5. C02 gas is trapped inside the coal mines.
Answer: False

Question 6. The quality of fuel is determined by its calorific value.
Answer: True

Question 7. Methane hydrate contains 13.3% methane. Bioethanol is a liquid biofuel.
Answer: False

Question 8. The source of solar energy is the nuclear fission reaction that takes place inside the Sun.’
Answer: False

Question 9. The chemical energy stored in biomass is called biomass energy,
Answer: True

Question 10. Solar panels are used in broadcast relay stations.
Answer: True

Question 11. The most widely used definition of sustainable development was produced by the report of the Brundtland Commission.
Answer: True

Question 12. Windmills usually convert electrical energy into mechanical energy.
Answer: False

Question 13. Bioethanol is a liquid biofuel.
Answer: True

Chapter 1 Environmental Concern Miscellaneous Type Questions Match The Columns:

Question 1

Column A	Column B
Chlorofluro-carbon	1. Non-conventional source of energy
Biofuel	2. Ozone layer depletion
Solar energy	3. Fossil fuel
Petroleum	4. Ethanol

Answer:
Chlorofluro-carbon: 2. Ozone layer depletion
Biofuel: 4. Ethanol
Solar energy: 1. Non-conventional source of energy
Petroleum: 3. Fossil fuel

Question 2

Column A	Column B
Greenhouse gas	1. Tidal energy
Renewable source of energy	2. Photovoltaic cell
Natural gas	3. Global warming
Solar energy	4. Methane

Answer:
Greenhouse gas: 3. Global warming
Renewable source of energy: 1. Tidal energy
Natural gas: 4. Methane
Solar energy: 2. Photovoltaic cell

Question 3

Column A	Column B
Turbulent sphere of atmosphere	1. Mesopause
Aurora borealis	2. Exosphere
The coldest region of the atmosphere	3. Troposphere
Hydrogen and helium gases are present	4. Ionosphere

 

Answer:
Turbulent sphere of atmosphere: 3. Troposphere
Aurora borealis: 4. Ionosphere
The coldest region of the atmosphere: 1. Mesopause
Hydrogen and helium gases are present: 2. Exosphere

WBBSE Solutions for Class 10 Physical Science and Environment