Energy:
Definition Of Energy:
―Energy is an agent which is responsible to do work.‖
OR
―The capacity or ability of doing some work is known as energy.‖
Kinds OR Types Of Energy:
i) Kinetic energy: The energy due to motion of a body is called Kinetic Energy.
Example: i) Moving ball can break a glass window ii) A striking hammer can drive a nail.
ii) Potential Energy: the energy which is possessed by a body by means of its position is known
as potential energy.
iii) Mechanical Energy: Energy of an object due to its motion or position
OR
A combination of kinetic and potential energy resulting from the force of gravity or the
movement or release of a machine component, such as a spring, clamp, or wheel.
iv) Chemical energy: energy in a substance that can be released by a chemical reaction. For
example: coal, petroleum are the source of chemical energy.
v) Electrical energy: energy made available by the flow of electric charge through a conductor.
vi) Heat energy: a form of energy that is transferred by a difference in temperature.
vii) Solar energy: Radiant energy emitted by the sun.
viii) Hydropower energy: The energy in flowing water is called Hydropower Energy.
ix) Nuclear energy: The energy released by a nuclear reaction, especially by fission or fusion.
Energy Resources:
Energy resources can be divided into two categories.
1) Renewable Resources Of energy
2) Non-Renewable Resources Of energy
Renewable Resources Of Energy:
Renewable energy is energy which is generated from natural sources i.e. sun, wind, rain, tides
and can be generated again and again as and when required. They are available in plenty and by
far most the cleanest sources of energy available on this planet. For e.g.: Energy that we receive
from the sun can be used to generate electricity. Similarly, energy from wind, geothermal,
biomass from plants, tides can be used this form of energy to another form.
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OR
The resources of energy which can be used again and again are known as renewable resources.
These are:
i) Solar energy: Solar energy is the energy derived from the sun through the form of solar
radiation.
ii) Wind energy: Wind power is the conversion of wind energy into a useful form of energy,
such as using wind turbines to make electricity, wind mills...
iii) Hydropower energy: Energy in water can be harnessed and used. Since water is about 800
times denser than air, even a slow flowing stream of water, or moderate sea swell, can yield
considerable amounts of energy.
iv) Tidal energy: Tidal power, also called tidal energy, is a form of hydropower that converts the
energy of tides into useful forms of power - mainly electricity.
v) Geothermal energy: Geothermal energy is power extracted from heat stored under the earth‘s
crust. This power source is generally cost effective, usually reliable, mostly sustainable, and
generally environmentally friendly.
Non-Renewable Resources Of Energy:
Renewable energy is energy which is taken from the sources that are available on the earth in
limited quantity and will vanish fifty-sixty years from now. Non-renewable sources are not
environmental friendly and can have serious effect on our health. They are called non-renewable
because they can be re-generated within a short span of time. Non-renewable sources exist in the
form of fossil fuels, natural gas, oil and coal.
OR
The resources of energy which can be used for a particular period of time, after that they may not
be available for the use of man. These include:
i) Coal: Coal is a combustible black or brownish-black sedimentary rock formed from fossilized
plants. Coal consists of amorphous carbon with various organic and some inorganic compounds
and is normally occurring in rock strata in layers or veins called coal beds.
ii) Gas: Natural gas is a combustible mixture of hydrocarbon gases that occurs with petroleum
deposits consisting primarily of methane. It is found with other fossil fuels and in coal beds and is
created by the decay of methanogenic organisms in marshes, bogs, and landfills. Lower
temperatures are likely to produce more petroleum, and higher temperatures are likely to produce
more natural gas.
iii) Oil: Petroleum, also known as crude oil, is a naturally occurring toxic combustible liquid
primarily made up of hydrocarbons. Petroleum is the result of partial decay of living organisms
occurring in the rock strata of certain geological formations.
iv) Nuclear fuels: Nuclear power is produced by controlled nuclear fission (splitting atoms). In
most cases nuclear power plants use nuclear fission reactions to heat water, using the steam to
produce electricity. Uranium, specifically, uranium -235, is one of the few elements easily
fissioned.
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v) Wood: Wood and wood products used as fuel, including round wood (cord wood), limb wood,
wood chips, bark, sawdust, forest residues, charcoal, pulp waste, and spent pulping liquor.
Non-Conventional Sources Of Energy:
Non-conventional sources of energy are those sources of energy which are not in common use at
this time but are being considered or explored to bring to routine use in the future. With the
exhaustion of conventional sources of energy the search for non-conventional sources of energy
have been intensified.
Conventional sources of energy are coal, gas, oil, wood and nuclear fuels. These sources are in
routine use nowadays.
Non-conventional sources of energy are solar energy, geothermal energy. Wind energy, tidal
energy and ocean thermal gradient.
Solar Energy:
The energy of the sun is called solar energy. It has been estimated that on the average 180,000
kilowatts solar energy is falling per square kilometre of the earth. Solar energy is utilized in two
ways.
A solar furnace contains thousands of mirrors to focus the sun rays. In this solar heater produces
heat used in industry or houses. The heaters heat up water or air. Solar energy can also be used
indirectly. Solar cells made up of panels of semi-conductors (usually silicon) are used which
when illuminated by sun generate electricity. These kinds of cells have frequently been used in
space probe. They have not become popular in domestic side due to high cost.
Wind Energy:
Energy obtained from wind by using wind mills is called wind energy. The wind rotates
generated which produce electricity.
Previously wind mills were used for grinding grains. The rotating wings of a wind mill can be
attached to a magnet which gives an electric current with rotation. Low power, high cost and
uncertainties of weather had not made power generation through wind power.
Geothermal energy:
Heat energy obtained from the hot molten metals inside the earth crust serves as the source of
thermal energy. This type of energy is present in the form of hot water and steam. Geothermal
electricity plants change the geothermal energy into electricity. Hot water of springs is being used
for power generation particularly in USA , Italy , and Japan etc. furthermore;hot springs are used
as geysers for heating the houses.
Nuclear Energy:
The most concentrated form of energy is in the atomic nuclei. This energy can be released by the
processes of fission or fusion.
Fusion reactions have been producing electricity in commercial quantities for about 30 years. In
megawatt of power to meet ur future domestic and industrial needs, we will have to generate
electricity from nuclear plants using (Uranium U-235) and plutonium s fuel.
Tidal Energy:
Energy which is obtained through the tidal waves of the sea is called tidal energy. Tidal waves of
sea strike the shore constantly. These waves are used to run electric generators which produce
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electricity. The kinetic energy of the tides is also used to produce other forms of mechanical
work. Tidal power station traps high tides behind a barrage. The water flows through turbines.
Greenhouse Effect:
The heating that occurs when gases such as carbon dioxide trap heat escaping from the Earth
and radiate it back to the surface; so-called because the gases are transparent to sunlight but
not to heat and thus act like the glass in a greenhouse.
OR
The overall warming of the earth's lower atmosphere primarily due to carbon dioxide and
water vapour which permit the sun's rays to heat the earth, but then restrict some heat-energy
from escaping back into space.
Greenhouse Gases:
i) Carbon dioxide CO2
ii) Methane
iii) Water Vapour
iv) Chloro Fluoro-Carbon (CFC)
v) Nitrous oxide
Mechanism OF Greenhouse Effects:
• Our Earth receives most of its energy, called radiation, from the Sun.
• This energy is electromagnetic radiation in the form of Visible light, with small amounts of
Infrared (IR) and Ultraviolet (UV).
• The incoming Visible solar energy has a very short wavelength and passes right through the
atmosphere.
• The Earth's surface absorbs the solar energy and releases it back to the atmosphere as
Infrared (IR) radiation, some of which goes right back into space.
• But some of the IR radiation emitted by the Earth is absorbed by greenhouse gases in the
atmosphere and sent back towards the Earth's surface.
• That warms the Earth's surface. Three main gases in our atmosphere that contribute to the
greenhouse effect are carbon dioxide, methane, and water.
• These gases absorb the infrared radiation emitted by the Earth and re-radiate the energy as
heat back towards the Earth, causing a warming known as the greenhouse effect.
• The warming due to greenhouse gases is expected to increase as humans add more
greenhouse gases to the atmosphere.
Sources Of Greenhouse Gases:
Carbon dioxide (CO2) is a colourless gas that's a by-product of the combustion of organic
matter. Today human activities are pumping huge amounts of CO2 into the atmosphere,
resulting in an overall increase in carbon dioxide concentrations.
Methane occurs naturally when organic material decomposes. Man-made processes produce
methane in several ways:
• By extracting it from coal
• From large herds of livestock (i.e., digestive gases)
• From the bacteria in rice paddies
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• Decomposition of garbage in landfills
Importance Of Greenhouse Effect:
Following is the importance of greenhouse effect.
i) Without greenhouse effect, the Earth would not be warm enough for humans to live.
ii) Without greenhouse gases, heat would escape back into space and Earth‘s average
temperature would be about 600 F colder.
Global Warming:
A gradual increase in the overall temperature of the earth's atmosphere generally attributed to the
greenhouse effect caused by increased levels of carbon dioxide, CFCs, and other pollutants
Causes Of Global Warming:
The main causes of global warming, in order of the magnitude of their impact, are:
1. Carbon Dioxide from:
A. Fossil Fuel
B. Deforestation
C. Failing Sinks
2. Methane from:
A. Cattle and Rice Paddies
B. the Arctic Tundra
C. Clathrates
3. Nitrogen Oxides from Farming
4. Other Gases
Effects OF Global Warming:
When it comes to global warming, harmful effects like melting polar ice caps, weather changes,
and an increase in diseases are changing the world and will ultimately affect your life. Below is
the list of effects that global warming is having on environment, climate and human kind.
1. Melting of glaciers: The melting of glaciers will create plethora of problems for human kind
and the animals living in the earth. Due to increased global warming, the level of the sea will rise
which will lead to flooding and this will in turn create havoc in human life. Apart from raising the
sea levels, it will also endanger several species of animals and thus will hamper the balance of the
ecosystem. Moreover these large glaciers reflect light back into the space and with meltdown of
these glaciers, earth will be further warmed.
2. Climate Change: Irregular weather patterns have already started showing results. Increased
precipitation in the form of rain has already been noticed in polar and subPolar Regions . More
global warming will lead to more evaporation which will cause more rains. Animals and plants
cannot easily adapt to increase rainfall. Plants may die due to it and animals may migrate to other
areas, which can cause entire ecosystem out of balance.
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3. Droughts: Large scale evaporation will be the major cause of droughts in many places
particularly Africa . Although, it is reeling under the huge pressure of water crisis, increased
global warming would further make the situation worse and will cause malnutrition.
4. Diseases: As the temperature becomes warmer, it will have an effect on the health of humans
and the diseases they are exposed to. With the increase in the rainfall, water borne diseases are
likely to spread specially malaria. The earth will become warmer and as a result heat waves are
likely to increase that will cause a major blow to the people particularly in Europe.
5. Hurricanes frequency: As the temperature of the oceans rises, hurricanes and other storms are
likely to become stronger. With the increase in the global warming the water in the ocean warms
up and it heats up the surrounding air, creating hurricanes. More water evaporation means more
hurricanes.
6. Agriculture: Global warming will affect agriculture. Although the results are not visible yet,
but it may show its colours in years to come. As the global temperature will increase plants will
find it harder to survive and will die. Plants are the major source of food for human beings and as
a result food shortage will occur. The shortage of the food may lead to war and conflicts in some
countries.
Steps To Control Global Warming:
i) Use Public Transport:
ii) Use Renewable Energy Like Wind Power:
iii) Burn Methane:
iv) Use Smart Cooler, Heater & Air Conditioner
v) Tune up and maintain vehicles properly
vi) Reduce electricity usage to the maximum
vii) Prefer recycling.
Ozone Depletion:
Ozone:
Ozone is a highly reactive and unstable gas, which is formed by the recombination of oxygen
(O2) atoms in the presence of intense radiation. Its symbol is O3.
Ozone Layer:
The ozone layer is a naturally occurring zone found in the stratosphere, situated between 10-15 kms above the surface of the Earth. The main function of the ozone layer is to act as a
shield against ultraviolet (UV) radiations from the Sun because these rays are harmful to life.
Ozone Depletion:
Destruction of the stratospheric ozone layer which shields the earth from ultraviolet radiation
harmful to life. ...
Causes Of Ozone Layer Depletion:
The Main Ozone-Depleting Substances (ODS)
• Chlorofluorocarbons (CFCs)
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• The most widely used ODS, accounting for over 80% of total stratospheric ozone depletion.
• Used as coolants in refrigerators, freezers and air conditioners in buildings and cars
manufactured before 1995.
• Found in industrial solvents, dry-cleaning agents and hospital sterilants.
• Also used in foam products — such as soft-foam padding (e.g. cushions and mattresses) and
rigid foam (e.g. home insulation).
• Halons
• Used in some fire extinguishers, in cases where materials and equipment would be
destroyed by water or other fire extinguisher chemicals. In B.C., halons cause greater damage
to the ozone layer than do CFCs from automobile air conditioners.
• Methyl Chloroform
• Used mainly in industry — for vapour degreasing, some aerosols, cold cleaning, adhesives
and chemical processing.
• Carbon Tetrachloride
• Used in solvents and some fire extinguishers.
• Hydro fluorocarbons (HCFCs)
• HCFCs have become major, ―transitional‖ substitutes for CFCs. They are much less
harmful to stratospheric ozone than CFCs are. But HCFCs they still cause some ozone
destruction and are potent greenhouse gases.
OR
The cause of ozone depletion is the increase in the level of free radicals such as hydroxyl radicals,
nitric oxide radicals and atomic chlorine and bromine. The most important compound, which
accounts for almost 80% of the total depletion of ozone in the stratosphere are
chlorofluorocarbons (CFC). These compounds are very stable in the lower atmosphere of the
Earth, but in the stratosphere, they break down to release a free chlorine atom due to ultraviolet
radiation. A free chlorine atom reacts with an ozone molecule (O3) and forms chlorine monoxide
(ClO) and a molecule of oxygen. Now chlorine monoxide reacts with an ozone molecule to form
a chlorine atom and two molecules of oxygen. The free chlorine molecule again reacts with ozone
to form chlorine monoxide. The process continues and the result is the reduction or depletion of
ozone in the stratosphere.
Effects Of Ozone Depletion
Following are the major effects of ozone layer depletion.
i) It will increase the risk of skin cancer
ii) It has resulted in melanomas, a kind of tumour.
iii) It greatly affects eyes and produces disease of vision.
iv) It suppresses immunity system of human beings.
v) UV rays damage various crops.
vi) It kills plankton and fish larvae.
vii) It causes sunburn in human beings.
viii) It causes spotting of leaves in plants and trees, thus decreases productivity of the plants.
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Acid Rain:
―The rainwater which contains a large amount of poisonous acids like sulphuric acid,
sulphurous acid, nitrous acid and other pollutants is known as the Acid Rain.‖
Formation of Acid Rain
Acid rain is caused by a chemical reaction that begins when compounds like sulphur dioxide
and nitrogen oxides are released into the air. These substances can rise very high into the
atmosphere, where they mix and react with water, oxygen, and other chemicals to form more
acidic pollutants, known as acid rain. Sulphur dioxide and nitrogen oxides dissolve very
easily in water and can be carried very far by the wind. As a result, the two compounds can
travel long distances where they become part of the rain, sleet, snow, and fog that we
experience on certain days.
Causes Of Acid Rain:
Human activities are the main cause of acid rain. Over the past few decades, humans have
released so many different chemicals into the air that they have changed the mix of gases in
the atmosphere. Power plants release the majority of sulphur dioxide and much of the
nitrogen oxides when they burn fossil fuels, such as coal, to produce electricity. In addition,
the exhaust from cars, trucks, and buses releases nitrogen oxides and sulphur dioxide into the
air. These pollutants cause acid rain.
OR
The main causes of acid rain are…
Natural Sources:
• Lightning strikes (cause nitrogen molecules to be oxidized)
• Combustion of hydrogen sulphide (hydrogen sulphide is formed from the breakdown of
sulphates in organic matter in the absence of oxygen- anaerobic conditions). This reaction forms
sulphur dioxide.
Human Sources:
• Combustion engines (car, airplanes etc.)
• Burning of fossil fuels and coal
• Some mineral ores contain sulphur dioxide, and this is released when the minerals are
processed.
Effect Of Acid Rain:
i) Kills flora and fauna
ii) Damages the buildings
iii) Causes skin cancer
iv) Increases the acidity of the soil
v) Kills fish and other aquatic animals
vi) Pollutes the water
vii) Causes spotting of leaves
viii) Causes corrosion of metal, painted surfaces and even stone buildings and monuments.
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