Chapter 1 – Concerns about our Environment

Concerns about our Environment
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Book Name : Physical Science and Environment
Subject : Physical Science
Class : 10 (Madhyamik)
Publisher : Oriental Book Company Private Limited
Chapter Name : Concerns about our Environment

Part 1.1

Physical Science and Environment

In-text Questions

Question 1.1.1

What are the major atmospheric layers?

Answer

The Earth’s atmosphere is divided into five major layers, which are:

  1. Troposphere: This is the lowest layer of the atmosphere, extending from the Earth’s surface to an altitude of about 7-20 kilometres.
  2. Stratosphere: This layer extends from the top of the troposphere to an altitude of about 50 kilometres.
  3. Mesosphere: This is the third layer of the atmosphere, extending from the top of the stratosphere to an altitude of about 85 kilometres.
  4. Thermosphere: This layer extends from the top of the mesosphere to an altitude of about 600 kilometres.
  5. Exosphere: This is the uppermost layer of the atmosphere, extending from the top of the thermosphere to the edge of space.

Question 1.1.2.

Name three gases present in the troposphere.

Answer

The troposphere is the lowest layer of the Earth’s atmosphere and it contains several gases, but three of the most abundant gases in the troposphere are:

  • Nitrogen (N2)
  • Oxygen (O2)
  • Argon (Ar)

Question 1.1.3.

Why the tropospheric atmosphere is turbulent?

Answer

The tropospheric atmosphere is turbulent for several reasons, including:

  1. Heating from the sun: The Earth’s surface is heated unevenly by the sun, which causes warm air to rise and cooler air to sink. This creates convection currents that stir the atmosphere and create turbulence.
  2. Atmospheric pressure differences: The air in the troposphere is constantly moving due to differences in pressure caused by temperature and humidity changes.
  3. Friction: Friction between the Earth’s surface and the air can cause turbulence, especially in areas with high wind speeds.

All of these factors contribute to turbulence in the tropospheric atmosphere. This turbulence can have important effects on weather patterns, air quality, and the distribution of pollutants and other substances in the atmosphere.

Question 1.1.4.

How does the density of air vary with an increase in altitude?

Answer

The density of air decreases as altitude increases. This is because the pressure in the Earth’s atmosphere decreases as altitude increases, and air density is directly proportional to atmospheric pressure.

Question 1.1.5.

In the stratosphere why there is a trend of increasing temperature with increasing altitude?

Answer

In the stratosphere, there is a trend of increasing temperature with increasing altitude due to the presence of the ozone layer. When sunlight enters the stratosphere, it is absorbed by ozone molecules, which causes the temperature of the surrounding air to increase.

Question 1.1.6.

Which is the coldest region of the atmosphere?

Answer

The coldest region of the Earth’s atmosphere is the mesosphere. The mesosphere is the third layer of the atmosphere, located above the stratosphere and below the thermosphere, and it extends from about 50 to 85 kilometres (31 to 53 miles) above the Earth’s surface.

Question 1.1.7.

What is the position of the ozone layer above the earth?

Answer

The ozone layer is located in the Earth’s stratosphere, specifically in the lower portion of the stratosphere. It extends from about 10 to 50 kilometres (6 to 31 miles) above the Earth’s surface.

Question 1.1.8.

Mention the manmade cause of ozone layer depletion.

Answer

The primary manmade cause of ozone layer depletion is the emission of chlorofluorocarbons (CFCs) and other halogenated organic compounds into the atmosphere. These chemicals were commonly used as refrigerants, solvents, and propellants in aerosol cans.

Question 1.1.9.

How the lives on the earth’s surface are protected from UV-ray from sun?

Answer

Life on Earth is protected from the harmful effects of ultraviolet (UV) radiation from the sun by the ozone layer, which is present in the Earth’s stratosphere. The ozone layer acts as a natural shield that absorbs most of the UV radiation from the sun, particularly the most harmful UV-C and a portion of UV-B radiation.

Question 1.1.10.

What may happen if there is no ozone layer above the earth’s surface?

Answer

In absence of the ozone layer entire UV radiations from the sun fall on the earth’s surface and mark the atmosphere near the earth’s surface as highly hot, as a result, biofurnance of the earth becomes a blast furnace.

Question 1.1.11.

Name two atmospheric gases of which one is responsible for the greenhouse effect and the other is not.

Answer

One atmospheric gas responsible for the greenhouse effect is carbon dioxide (CO2). An atmospheric gas that is not responsible for the greenhouse effect is nitrogen (N2).

Exercise Questions

Multiple-Choice Questions

Question 1.

For the protection of the environment from pollution, the involvement necessary of 

  1. Only local government
  2. Pollution control board
  3. Environmentalist
  4. All people including masses at the grass root level

Answer

(d) All people including masses at the grass root level

Question 2.

Which of the following subjects may be included under physical science?

  1. Zoology 
  2. Genetics
  3. Biotechnology
  4. Chemistry

Answer

(d) Chemistry

Question 3.

Our atmosphere extends up to how much height over the earth.

  1. 1200 km
  2. 500 km
  3. 800 km
  4. 16 km

Answer

(b) 500 km

Question 4.

Which of the following gases is responsible for ozone layer depletion?

  1. Troposphere
  2. Stratosphere
  3. Mesosphere
  4. Thermosphere

Answer

(a) Troposphere

Question 5.

Which of the following gases is responsible for ozone layer depletion?

  1. O2
  2. NO
  3. N2
  4. All of these

Answer

(b) NO

Very Short Answer (VSA)

Question 1.

  1. What is the temperature of the atmosphere layer at a height of 50 km?
  2. The coldest temperature of the atmosphere is at which region of the atmosphere?
  3. In the atmosphere, where ozone layer present?
  4. Which gas is not a greenhouse gas?
  5. Does manmade gas destroy the ozone layer?

Answer

  1. The temperature attains a maximum of -2oC (271 K).
  2. The coldest region of the Earth’s atmosphere is the mesosphere.
  3. The ozone layer is present in the Earth’s stratosphere.
  4. Nitrogen (N2)
  5. Chlorofluorocarbons (CFCs)
Question 2.

Fill up the blanks: 

  1. The ozone layer shields the earth from ___________ radiation.
  2. Ozone hole first detected over the _____________.
  3. Nitrogen is not a ____________ gas.
  4. ___________ is a branch of physical science.

Answer

  1. The ozone layer shields the earth from harmful ultraviolet (UV) radiation.
  2. Ozone holes were first detected over the Antarctic.
  3. Nitrogen is not a greenhouse gas.
  4. Physics is a branch of physical science.

Question 3.

Supply the missing word from these in brackets: 

  1. N2 and O2 are present in ____. (Troposphere, Mesosphere)
  2. Atmospheric pressure with ____ increase of altitude (increases, decreases)
  3. Ozone is an ____ of oxygen. (isotope, allotrope)
  4. N2 and O2 ____ solar radiations on the earth. (allow, do not allow)

Answer

  1. N2 and O2 are present in Troposphere.
  2. Atmospheric pressure with decreases increases of altitude.
  3. Ozone is an allotrope of oxygen.
  4. N2 and O2 do not allow solar radiation on the earth.
Question 4.
Indicate which of the following statements is true and which is false: 
  1. In Troposphere atmospheric pressure decrease exponentially with the increase in altitude.
  2. In the stratosphere temperature rise with an increase in height due to the presence of ozone.
  3. The stratospheric atmosphere is calm and quiet.
  4. The increase in cases of skin cancer in south Australia is due to the ozone hole.

Answer

  1. False,
    The correct statement is that atmospheric pressure decreases linearly with the increase of altitude in the troposphere.
  2. True
  3. False,
    The stratospheric atmosphere is not calm and quiet. It is turbulent and contains strong winds, particularly in the region of the polar vortex.
  4. True

Short Answer Type Questions:

Question 1.

What are the subdivisions of the atmosphere?

Answer

The atmosphere is divided into five main subdivisions or layers, based on differences in temperature and other physical properties. These layers, listed from the surface of the Earth upward, are:

  1. Troposphere: This is the lowest layer of the atmosphere, extending from the Earth’s surface to an average height of about 7 to 20 kilometres (4 to 12 miles) depending on the location.
  2. Stratosphere: This layer extends from the top of the troposphere up to an average height of about 50 kilometres (31 miles).
  3. Mesosphere: This layer extends from the top of the stratosphere up to an average height of about 85 kilometres (53 miles).
  4. Thermosphere: This layer extends from the top of the mesosphere up to an altitude of about 600 kilometres (373 miles).
  5. Exosphere: This is the outermost layer of the atmosphere, extending from the top of the thermosphere up to an altitude of about 10,000 kilometres (6,200 miles) or more.

Question 2.

What are the chemical species present in the troposphere?

Answer

The troposphere is the lowest layer of the atmosphere, and it is where most of the Earth’s weather occurs. The major chemical species present in the troposphere are:

  • Nitrogen (N2): This is the most abundant gas in the troposphere, making up about 78% of the atmosphere.
  • Oxygen (O2): This is the second most abundant gas in the troposphere, making up about 21% of the atmosphere.
  • Water vapor (H2O): This is the third most abundant gas in the troposphere, and its concentration varies with altitude and location.
  • Carbon dioxide (CO2): This gas makes up about 0.04% of the troposphere, but its concentration is increasing due to human activities.
  • Other gases: The troposphere also contains small amounts of other gases, such as argon, ozone, methane, and nitrous oxide.

Question 3.

Why the atmosphere of the troposphere is turbulent?

Answer

The atmosphere of the troposphere is turbulent due to the uneven heating of the Earth’s surface by the Sun. As the Sun warms different areas at varying rates, it creates temperature gradients, causing warm air to rise and cool air to sink. This constant movement of air leads to turbulence. Additionally, factors like topography, friction, and weather systems further contribute to the turbulence in this layer of the atmosphere, shaping weather patterns and natural processes.

Question 4.

What is the reason for the increasing warming tendency with increasing altitude in the stratosphere?

Answer

The presence of ozone (O3) in the stratosphere is the primary reason for the increasing warming tendency with increasing altitude. Ozone absorbs incoming UV radiation from the sun, releasing heat that warms the surrounding air, making the stratosphere warmer than the layers below it.

Question 5.

Give equations for ozone formation.

Answer

Ozone formation involves a series of chemical reactions between oxygen molecules, ozone molecules, and atomic oxygen. Here are the basic equations for ozone formation:

  1. O2 + photon (UV ray) → 2O
  2. O + O2 → O3 (ozone)
  3. O3 + photon (UV ray) → O2 + O

The net reaction for ozone formation is:

3O2 + photon (UV radiation) → 2O3

This reaction shows that three molecules of oxygen (O2) and a photon of UV radiation combine to produce two molecules of ozone (O3).

Question 6.

Give two reasons for the ozone layer depiction.

Answer

The depletion of the ozone layer is primarily caused by:

  1. Man-made chemicals such as chlorofluorocarbons (CFCs), halons, and other ozone-depleting substances (ODSs).
  2. Natural phenomena such as polar stratospheric clouds, can provide a surface for chemical reactions that convert benign forms of chlorine and nitrogen into ozone-destroying forms.

Question 7.

Mention two harmful effects of ozone layer destruction.

Answer

Destruction of the ozone layer can cause :

  1. Cancer to human skin.
  2. Damage the cornea of the eyes and develops a premature cataract.

Long Answer (LA) type Questions :

Question 1.

How environmental protection can be achieved?

Answer

Environmental protection can be achieved in the following ways :

  1. Reduction in the use of fossil fuel.
  2. Ban the extensive use of CFCs.
  3. Conservation of forest.
  4. Effective check on the growth of the population.
  5. To develop environmentally compatible technologies.

Question 2.

Give two examples of environmental pollution that can be explained by physical science.

Answer

The two environmental pollutions which can be explained by physical science are:

  1. Greenhouse effect: The buildup of greenhouse gases, such as carbon dioxide (CO2), in the atmosphere leads to the greenhouse effect. Physical science principles such as radiative transfer, thermodynamics, and atmospheric chemistry explain how greenhouse gases trap heat, how their concentrations are changing, and how they interact with other components of the Earth’s climate system.
  2. Ozone layer depletion: Physical science principles such as atmospheric chemistry and thermodynamics can be used to explain the depletion of the ozone layer.

Question 3.

Explain the reason for turbulent air circulation in the troposphere.

Answer

The turbulent air circulation in the troposphere is mainly caused by differences in temperature and pressure across the Earth’s surface. The Sun’s energy is absorbed unequally by the Earth’s surface, causing some areas to become warmer than others. This creates temperature and pressure gradients that drive the movement of air masses.

Warmer air is less dense than cooler air, so it rises and creates areas of low pressure. Cooler air is denser than warmer air, so it sinks and creates areas of high pressure. As air moves from high-pressure areas to low-pressure areas, it creates winds and generates turbulence. The rotation of the Earth also affects the movement of air, creating different wind patterns in the Northern and Southern hemispheres.

Question 4.

Describe the formation of the ozone layer.

Answer

The ozone layer forms in the Earth’s stratosphere primarily through the interaction of solar ultraviolet (UV) radiation with oxygen molecules (O2). UV radiation breaks apart O2 molecules into individual oxygen atoms, and some of these oxygen atoms then react with other O2 molecules to create ozone (O3). This ozone absorbs and scatters a significant portion of the incoming harmful UV radiation, providing vital protection for life on Earth. This process is known as the ozone-oxygen cycle and plays a critical role in maintaining the ozone layer’s stability and its role in shielding us from harmful UV rays.

Ozone formation involves a series of chemical reactions between oxygen molecules, ozone molecules, and atomic oxygen. Here are the basic equations for ozone formation:

  1. O2 + photon (UV ray) → 2O
  2. O + O2 → O3 (ozone)
  3. O3 + photon (UV ray) → O2 + O

Question 5.

Describe the causes of ozone layer destruction.

Answer

The destruction of the ozone layer is primarily caused by the emission of human-made chemicals known as ozone-depleting substances (ODSs), which include chlorofluorocarbons (CFCs), halons, and other compounds. These substances can rise into the stratosphere where they are broken down by UV radiation, releasing chlorine and bromine atoms that can react with ozone molecules, breaking them down and reducing the overall amount of ozone in the atmosphere. This process is known as ozone depletion. Other factors such as volcanic eruptions and changes in solar radiation can also affect the amount of ozone in the atmosphere, but human-made ODSs are the primary cause of ozone layer destruction.

Question 6.

What is an ozone hole? Where it is found and mention its consequence.

Answer

Ozone hole:  An ozone hole refers to a region of severe ozone depletion that occurs over Antarctica during the Southern Hemisphere spring (September-November).

Consequences of ozone hole: The creation of an ozone hole will allow the harmful ultraviolet rays of the sun to enter the earth’s atmosphere. This will cause several diseases like skin cancer, damage to the cornea of the eyes, infertility, skin diseases, death of fishes and other aquatic life, wilting of leaves of plants, etc.

Part 1.2

Rational Use of Energy

In-text Question

Question 1.2.1

What are fossil fuels?

Answer

Fossil fuels are a non-renewable energy source formed from the remains of dead plants and animals that lived millions of years ago. These fuels include coal, oil, and natural gas.

Question 1.2.2

Why the dependence on fossil fuels should be reduced?

Answer

The dependence on fossil fuels should be reduced for the following reasons

  • Fossil fuels have negative impacts on the environment, including air and water pollution, greenhouse gas emissions, and climate change
  • They are a finite resource and will eventually run out, creating energy security concerns
  • There are cleaner and more sustainable alternatives, such as renewable energy sources, that can be used to reduce dependence on fossil fuels

Question 1.2.3

What are sustainable sources of energy?

Answer

Sustainable sources of energy are renewable and clean sources of energy that can be replenished naturally and do not emit harmful pollutants or greenhouse gases. These sources include solar, wind, geothermal, hydro, and biomass energy, as well as new technologies like wave and tidal power.

Question 1.2.4

Between biomass and petroleum which is the renewable source of energy?

Answer

Biomass is a renewable source of energy, while petroleum is a non-renewable source of energy. Biomass is derived from organic matter such as plants, trees, and agricultural waste that can be replenished over time, while petroleum is a fossil fuel formed from the remains of dead organisms that lived millions of years ago and is a finite resource that cannot be replenished within a human time scale.

Question 1.2.5

Which forms of energy is the permanent solution of our energy crisis?

Answer

Forms of energy solution for our energy crisis:

  1. Solar cells
  2. Wind energy
  3. Tidal energy
  4. Geothermal energy
  5. Biomass energy
  6. Bio-gas

Question 1.2.6

What are the main materials needed to prepare a solar cell?

Answer

Thin wafers of semiconductor materials like silicon and gallium are used as the main material for the preparation of solar cells.

Question 1.2.7

Tidal energy is converted to which energy for use?

Answer

Tidal energy is typically converted into electrical energy for use.

Question 1.2.8

How geothermal energy is converted to electric energy?

Answer

Concerns about our Environment

Geothermal energy is converted into electrical energy using a geothermal power plant. The process involves drilling deep wells into the Earth’s crust to access hot water and steam that is heated by the Earth’s geothermal heat. The hot water and steam are then used to drive turbines, which generate electricity. There are several types of geothermal power plants, including dry steam, flash steam, and binary cycle power plants, each with different methods of capturing and utilizing geothermal energy to generate electricity.

Question 1.2.9

What do you mean by bio-mass? Is it a renewable energy source?

Answer

Organic matter used as a fuel, especially in a power station for the generation of electricity is called biomass. Yes, it is a renewable source.

Question 1.2.10

Mention some advantages of the use of biogas.

Answer

Advantages of the use of Biogas :

  1. It is clean, non-polluting and cheap.
  2. It is used directly from the plant and there is no storage problem.
  3. It contains 75% methane, which has a high calorific value and acts as good fuel.

Question 1

List four forms of energy that you use from morning to night when you go to bed.

Answer

Four forms of energy that a person may use from morning to night when going to bed include:

  1. Electrical energy
  2. Chemical energy
  3. Mechanical energy
  4. Thermal energy

Question 2

What are the sources of these forms of energy?

Answer

  1. Electrical energy:
  • Fossil fuels such as coal, natural gas, and oil
  • Nuclear power
  1. Chemical energy:
  • Food and beverages
  • Biofuels
  1. Mechanical energy:
  • Fossil fuels such as gasoline and diesel used in cars and other vehicles
  • Renewable energy sources such as wind, hydro, and tidal power used to generate electricity
  1. Thermal energy:
  • Fossil fuels such as coal, natural gas, and oil used for heating and cooling
  • Renewable energy sources such as solar and geothermal power used for heating and cooling

Activity 1.2.3.

Question 1 

Out of various fuels which will be your option for cooking your food?
(a) What are the criteria when you categorise it as a good fuel?
(b) What would be your choice when you are in
(i) a forest
(ii) remote village
(iii) Mumbai
(iv) five centuries ago.

Answer

It is generally recommended to use cleaner and more sustainable forms of fuel for cooking, such as LPG, electric cooktops.

(a) Criteria for a good fuel :

  1. It should have a high calorific value to ensure efficient cooking.
  2. It should burn cleanly and produce minimal or no harmful emissions.
  3. It should be readily available, affordable, and easy to use.
  4. It should be sustainable and renewable to reduce its impact on the environment.

(b) The choice of fuel for cooking will depend on the availability, accessibility, and cultural preferences of the region. Here are some examples:

  1. In a forest, dry wood or plant materials like dried leaves and twigs can be used as fuel for cooking. However, it is essential to be mindful of the environmental impact and potential fire hazards of collecting wood from the forest.
  2. In a remote village, a good choice could be biogas or biomass, such as dried animal dung or agricultural waste, which can be easily converted into fuel.
  3. In a city like Mumbai, a common choice for cooking fuel is LPG (Liquefied Petroleum Gas), which is clean, efficient, and readily available.
  4. Five centuries ago, the most common cooking fuel was wood, dried animal dung, and other biomass. Coal was also used in some regions. However, the environmental impact and efficiency of these fuels were not as well understood as they are now.

Question 2

How are the factors different in different cases?

Answer

Availability, cost, and safety were likely the main factors considered in the choice of fuel.

Exercise Questions

Multiple choice questions (MCQ) :

Question 1.

Which of the following energy sources is not responsible for global warming?

  1. Fossil fuels
  2. Solar energy
  3. Methane hydrate
  4. All

Answer

(b) Solar energy

Question 2.

Among the following fuels whose quality is most bad?

  1. Coal
  2. Petrol
  3. LPG
  4. Methane

Answer

(a) Coal

Question 3.

Which one of the following is not a renewable energy source?

  1. Tidal energy
  2. Biomass energy
  3. Pertrol
  4. Solar energy

Answer

(c) Petrol

Question 4.

Which one is the source of all energy?

  1. Solar
  2. Coal
  3. Petroleum
  4. Electric

Answer

(a) Solar

Question 5.

The minimum wind speed requires for running a windmill is-

  1. 50 km/hr
  2. 15 km/hr
  3. 25 km/hr 
  4. 10 km/hr

Answer

(b) 15 km/hr

Very Short Answer Type Questions (VSA) :

1. Answer the following questions:

Question 1.

Why do high and low tides occur in the sea?

Answer

High and low tides occur in the sea due to the gravitational pull of the Moon and the Sun on Earth’s oceans.

Question 2.

Tidal energy is converted to what form of energy for use?

Answer

Tidal energy is typically converted into electrical energy for use.

Question 3.

Where in the world geothermal energy is used to generate electricity?

Answer

In hot springs.

Question 4.

Name a petrocrop.

Answer

Coal, oil, and natural gas

Question 5.

What is the name of the anaerobic bacteria used for the fermentation of biomass?

Answer

Methanogenic bacteria.

Question 2.

Fill in the blanks :

  1. Natural gas contains ____ % CH4.
  2. Forest wood is a ____ source of energy.
  3. The main constituent of gobar-gas is ____.
  4. Wind farms are located in ____ regions.

Answer

  1. Natural gas contains 70-90% CH4.
  2. Forest wood is a renewable source of energy.
  3. The main constituent of gobar gas is methane (CH4).
  4. Wind farms are located in windy regions.

Question 3.

Supply the missing word from these in the brackets:

  1. The material needs to prepare solar cell _____ [silicon/ sodium]
  2. Biogas contains mainly _____ [CH4/C2H5]
  3. The calorific value of methane is _____ KJ/g. [55/100]
  4. Carbon black is prepared from _____ [methane/coal]

Answer

  1. The material need to prepare solar cells is silicon.
  2. Biogas contains mainly CH4.
  3. The calorific value of methane is 55 KJ/g.
  4. Carbon black is prepared from Coal.

Question 4.

Indicate which of the following statements is true and which is false:

  1. The calorific value of fuel determines its quality.
  2. The calorific value of coal is higher than that of L.P.G.
  3. The burning of fossil fuels is responsible for global warming.
  4. Wind energy is a source of renewable energy.

Answer

  1. True
  2. False. Liquefied Petroleum Gas (L.P.G.) has a higher calorific value than coal.
  3. True
  4. True

Question 5.

Match the columns (left with right)

Left Column Right Column
1.  Renewable source of energy
2. Petroleum
3. Natural gas
4. Fire ice
5. Greenhouse effect
(a) Fossil fuel
(b) Tidal energy
(c) Methane hydrate
(d) Methane
(e) coal mine
Answer
  1. Renewable source of energy – (b) Tidal energy
  2. Petroleum – (a) Fossil fuel
  3. Natural gas – (e) coal mine
  4. Fire ice – (c) Methane hydrate
  5. Greenhouse effect – (d) Methane

Short Answer Type Questions. 

Question 1

Define calorific value. Between petrol and LPG whose calorific value is higher?

Answer

The amount of heat released when one gram of fuel is burnt in a sufficient supply of oxygen is called the calorific value of that fuel.

LPG has a higher calorific value.

Question 2

What are fossil fuels? Mention the harmful effects of their burning.

Answer

Fossil fuels are non-renewable energy sources that are formed over millions of years from the remains of plants and animals that lived long ago.

Harmful effects:

  1. It is a non-renewable source of energy.
  2. Excess burning of fossil fuels causes air pollution and global warming.
  3. The health of organisms also gets affected due to the burning of excess fuels.

Question 3

Classify the natural sources of energy with examples

Answer

Natural sources of energy:

  1. Renewable sources: For example, forests, wildlife, wind energy, bio-mass energy, tidal energy, hydropower, and solar energy.
  2. Non-renewable sources: For example, coal and petroleum.

Question 4

What is a solar cell and how much electricity it produces?

Answer

A solar cell is an electronic device that converts sunlight into electricity through the photovoltaic effect. Generally, a typical solar panel of around 1 square meter can produce between 200 to 400 watts of power under direct sunlight.

Question 5

Mention some uses of solar cells.

Answer

Uses of solar cells:

  1. Extensively used in calculators, toys, electronic watches, and street lighting.
  2. Used in artificial satellites for electricity generation.
  3. Used in remote areas where conventional electricity supply is a problem.

Question 6

What is bio-mass? Mention its uses.

Answer

The waste and dead parts of living beings like plants, tree and animals, is called biomass.

Uses of biogas:

  1. It is pollution-free and uses waste material for the generation of energy.
  2. Biogas is used as a fuel to run engines and for generating electricity.

Question 7

Mention the use of Gobar-gas.

Answer

Uses of Gobar-gas:

  1. Small gobar-gas plants are used for household heating purposes.
  2. It can also be used in a gas engine to produce electricity.
  3. Used as Illuminant for domestic, and street lighting purposes.

Question 8

What is methane hydrate?

Answer

Methane hydrates are white, ice-like solids inside of which methane molecules are trapped.

Long Answer (LA) type Questions :

Question 1

Write notes on calorific value.

Answer

Calorific value is the amount of energy released when a substance is burned. It is a measure of the heating value of a fuel and is typically expressed in units of energy per unit of mass, such as joules per gram (J/g) or kilocalories per gram (kcal/g).

The calorific value of a fuel is an important parameter in determining its usefulness for various applications, such as heating, electricity generation, or transportation. Fuels with a higher calorific value are able to produce more energy per unit of mass, which makes them more efficient and cost-effective.

Question 2

Why use of fossil fuels should be reduced?

Answer

The use of fossil fuels should be reduced for the following reasons:

  1. It is a non-renewable source of energy and is present in a limited amount.
  2. Excess burning of these fuels causes air pollution.
  3. Human health gets affected
  4. Global temperature increases due to the emission of greenhouse gases from fuels.
  5. Drastic weather changes occur due to the pollution caused by fuel which affects agriculture.

Question 3

What do you mean by sustainable development?

Answer

Sustainable development is a principle for sustaining finite resources necessary to provide for the needs of future generations of life on our planet. Sustainable Development is a process that meets the needs of the present without compromising the ability of future generations to meet their own needs. Sustainable development constantly seeks to achieve social and economic progress in ways that will not exhaust all the earth’s finite natural resources.

Question 4

Write the principle to generate electricity using wind energy.

Answer

Wind possesses kinetic energy. This wind flow can be converted to electricity by using turbines. A wind turbine is basically the opposite of a fan. Wind turbines use the wind to make electricity. It has long blades. The wind turns the blades, which spin a shaft that is connected to a generator and electricity is produced.

Question 5

Write the principle to utilize tidal energy to produce electricity.

Answer

The tidal energy is harnessed by constructing a tidal barrage. During high tide, the sea water flows into the reservoir of the barrage and turns the turbine and produces electricity and during low tides, water from the reservoir flows back to the sea producing electricity.

Question 6

How bio-diesel is obtained?

Answer

Biodiesel is a form of diesel fuel derived from plants or animals and consisting of long-chain fatty acid esters. It is typically made by chemically reacting lipids such as animal fat (tallow), soybean oil, or some other vegetable oil with alcohol, producing a methyl, ethyl or propyl ester.

Question 7

Write notes on the production of electricity using urban and municipal solid wastes.

Answer

In many metropolitan cities, solid wastes are being utilized to produce electricity. Solid wastes are burnt and the heat generated is used to produce steam, which ultimately rotates a turbine to produce electricity. However, solid wastes available in metropolitan cities contain a large variety of materials, and some of them can cause serious environmental pollution during their burning.

Question 8

What are methanogenic bacteria? What is their use? Mention the use of biogas

Answer

Methanogenic bacteria are anaerobic microorganisms which generate gases like methane, carbon dioxide, hydrogen and hydrogen sulphide on the decomposition of organic materials to produce biogas.

It is used in the decomposition of organic waste materials of plants and vegetables for the production of biogas.

Uses of biogas:

  1. It is used for domestic heating and cooking purpose.
  2. Slurgy produces after the decomposition and used as fertilizers.

Also checkout: Class 10 Physical Science Formula List

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