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Physics Chapter – 8 : Our Environment

13 August, 2024

Our Environment

Natural Resources – A Resource which exists in nature is called a Natural Resource. It is not produced by any human being; rather it is available in nature itself. Human beings and other animals depend upon these resources for their existence.

Natural Resources present on the earth are:

  • Air – The atmosphere which contains different gases such as Oxygen, Nitrogen and carbon dioxide which are required for the survival of life on earth.
  • Water – The hydrosphere which covers almost 75% of the Earth surface. It is a home to an abundance of animals and plants and is also required for the survival of life on earth.
  • Land – The upper crust of the earth is called Lithosphere where different kinds of soils are found which are necessary for the growth of plants and are a home to several vitamins and minerals.
  • Biosphere – Life on Earth is possible because of the presence of these three major sources. A zone where the lithosphere, the atmosphere and the hydrosphere intersect and the life sustains is called the Biosphere.

The biosphere can be divided into two parts:

  • Abiotic Components – The non-living things such as air, water and land
  • Biotic Components – The living things such as plants and animals

Air


An atmosphere is a layer of gases that surrounds a planet. Atmospheric air has 78% nitrogen, 21% oxygen and, 1% of other gases by volume.

Role of atmosphere
The atmosphere keeps the average temperature of earth steady. It slows down the escape of heat into outer space during the night and prevents a sudden increase in temperature during the day.

Air pollution

  • It  is caused by the introduction of pollutants, organic molecules, or other unsafe materials into Earth’s atmosphere
  • Causes: Man-made sources include combustion of fuel, smoke from industries, Burning crackers etc. Natural sources include forest fires, volcanoes, etc.
  • Effects: Respiratory diseases, Global warming, Acid Rain, etc.

Ozone layer
The ozone layer is a thin part of the Earth’s atmosphere, which functions as a shield over the Earth’s stratosphere and absorbs the greatest amount of the Sun’s ultraviolet (UV) radiation.  The ozone layer comprises high concentrations of ozone (O3) in relation to other parts of the atmosphere.

Ozone layer depletion
it is the reduction of the amount of ozone in the stratosphere which results in greater UV radiations reaching the earth surface.

CFCs-
Chlorofluorocarbon (CFC) is an organic compound that contains carbon, chlorine and fluorine

Greenhouse effect-
The greenhouse effect is the natural phenomenon, which occurs when the greenhouse gases present in the Earth’s atmosphere trap solar radiation. Carbon dioxide (CO2), methane (CH4), ozone (O3), chlorofluorocarbons (CFCs), nitrous oxide (N2O) and water vapour (H2O) are called greenhouse gases.

Global Warming
The temperature of the earth rises due to the presence of greenhouse gases in it such as carbon dioxide and methane.

Water


Role of water in everyday life: Water forms two-thirds of our body, it keeps the body’s temperature normal. It is also used for agricultural purposes, Domestic Purposes, Industrial Purposes, etc. Distribution of water on earth: Only 3% of the water on the surface is fresh, the remaining 97% resides in the ocean.

Water pollution-Water pollution is the contamination of water bodies, caused by discharging pollutants directly or indirectly into the fresh and clean water bodies without adequate treatment.

The main causes of water pollution are

  • Urbanisation.
  • Industries
  • Agriculture
  • Religious and Social Practices
  • Withdrawal of water and drying up of water bodies

Water cycle
The water cycle, also known as the hydrologic cycle, is the continuous movement of water from the earth’s surface to the atmosphere and then back to the ground.

Transpiration
Transpiration is the biological process by which water is lost in the form of water vapour from the aerial parts of the plants called stomata.

Evaporation
it is a process by which a liquid or solid is transformed into vapour.

Biochemical Cycles-
it refers to the natural cycle of the earth through which a chemical substance or matter moves through the biotic and abiotic components of the earth. These components always interact with each other and form a stable system in the biosphere.

There are four main biogeochemical cycles

  • The Water Cycle
  • The Nitrogen Cycle
  • The Carbon Cycle
  • The Oxygen Cycle

Carbon cycle-
The circulation and transformation of carbon between living things and the environment is called the Carbon Cycle

Nitrogen Cycle
The nitrogen cycle is the recycling and reusing of nitrogen in different forms to meet the demands for various environmental activities.

Nitrogen fixation –
For nitrogen to be available to make proteins, DNA, and other biologically important compounds, it must first be converted into a different chemical form. The process of converting N2 into biologically available nitrogen is called nitrogen fixation.

Denitrification-
it is the process that converts nitrate to nitrogen gas, thus removing bioavailable nitrogen and returning it to the atmosphere.

Oxygen Cycle

  • It is a biological process which helps in maintaining the oxygen level.
  • Photosynthesis is a biological process used by plants to prepare their food with the help of sunlight and energy

Green Revolution –
The introduction of modern technology and equipment, usage of fertilizers and high-quality seeds.

White Revolution –
Increasing the growth of milk production by introducing dairy development programs.

Composting-
The process of recycling farm waste material by decomposing it is called Composting. The product formed on decomposition is called Compost.

 The composed has a high variety of nutrients and organic matter. The material used in the preparation of compost is animal excreta, sewage waste, vegetable waste and weeds.

Compost Vermicompost 
A manure prepared from waste materials such as cow dung, sewage, vegetable wastes and domestic wasteA manure that is prepared by using Earthworms
Takes around 3 to 6 months in formation Takes around 1 to 2 months in formation
The microbes decay the matter and manure is formedEarth worms reduce the matter and compost is formed

Green Manure –
sometimes specific plants are grown and then ploughed again in the soil. These plants decay and turn into manure which enriches the soil, mainly with nitrogen and phosphorus. Plants that are used in the production of green manure are hemp, clover, peas grass mixtures

How are fertilizers and manure different

ManureFertilizers
Manure provides humus to the soil Fertilizers do not provide humus to the soil
Manures are less rich in nutrients Fertilizers are highly rich in nutrients
Long term usage of manure leads to increment in the
 fertility of the soil
Long term usage of fertilizers can lead to decrease
 in the soil fertility

Rain Water Harvesting

Rainwater Harvesting- 
Instead of just letting the rainwater flow away farmers often store it in the reservoir tank. This water can we for the used for irrigational purposes. 

Water harvesting-

  • Water harvesting encourages soil and water conservation in order to sustain and increase biomass.
  • Increases income for the local community but also alleviates floods and droughts.
  • Examples: Rajasthan’s tanks, Khadins, and Nadis, Maharashtra’s Tals and Bandharas, Madhya Pradesh’s and Uttar Pradesh’s Bundhis, Bihar’s Pynes and Ahars, Himachal Pradesh’s Kulhs, Kattas in Karnataka, ponds in the Kandi belt of Jammu region, and Eris (tanks) in Tamil Nadu, Kerala’s Surangams.
  • Water harvesting constructions are crescent-shaped earthen embankments/concrete check dams built in areas that are seasonally flooded
  • The main purpose is to recharge groundwater.

Law of conservation of energy-

  • Energy can neither be created nor destroyed; rather, it transforms from one form to another.
  • In biological systems, it gets passed from one organism to another across trophic levels.

Energy flow-

  • Transfer of energy from one trophic level to another depicting its direction and amount.
  • Can be represented by the pyramid of energy.
  • In any food chain, only 10% of the energy is transferred from one trophic level to another.

Food chain-
A series of organisms each dependent on the next as a source of food.

Food web-

  • Is formed by interconnections of different food chains.
  • Is a graphical representation of ‘Who eats Whom’ in an ecosystem.

Characteristics of ecosystem-

•Includes the summary of trophic levels.

•Their energy flow and pyramids.

Environment-

•Includes all living and non-living things.

•Unlike ecosystem, there need not be any necessary interaction between them.

Garbage management-

•Involves all the activities and actions required to manage waste from its inception to its final disposal.

•Ensures environmental best practices are followed along with proper monitoring and regulation.

Steps involved:
1. Segregation of waste
2. Collection
3. Transport
4. Treatment
5. Processing & Recycling
6. Disposal

Reduce, recycle and reuse-

The 3 Rs to save the environment can be performed by each individual in our society:

  • Reduce:
    Reducing our usage and wasteful habits. Eg. Not wasting food, turning off the switches to save electricity, repairing leaky taps, reducing the amount of water used for bathing, etc.
  • Reuse:
    Using things again instead of discarding them. For example, reusing plastic utensils and bottles. Many things cannot be recycled or require a lot of energy, instead, we can utilize them for other purposes.

Recycle:
Collecting discarded paper, plastic, glass or metal objects to manufacture different products rather than synthesizing them from scratch. Must have a mechanism to segregate and dispose of each type of waste separately.

Sustainable development-

  • Sustainable development needs all stakeholders of forest resources to be satisfied.
  • In reality, industries use forests at rates far below the market rates which causes conflict between local dwellers and industrialists.

Chipko movement-

  • The Chipko Andolan (‘Hug the Trees Movement’) is one such case of conflict between the industrialist and local dwellers in the 1970s.                                                                             
  • Originated in Reni Garhwal, high up in the Himalayas.

The conflict between local villagers and logging contractor → Women of the village stopped felling of trees by hugging them → Contractor had to reverse the action.

  • The movement quickly gained popularity and media attention and forced the government to rethink the management of forest resources.
  • Involvement of local people is equally important in the management of forest resources.

Fuels: Materials that are burnt and used to store energy are defined as fuels. For Example, Wood, Coal etc.

Features of Good Fuel-

  • It should have high calorific value.
  • It should not produce smoke while burning.
  • Cheap and easily available.
  • Easy to handle and safe to transport.
  • Convenient in storage.

Sources of Energy 
There are two types of Sources of Energy – Conventional Sources of Energy and Non-conventional Sources of Energy.

Conventional sources of energy include the fossil fuels such as coal and petroleum. Non-conventional sources include solar cooker, solar cell panel etc.

Fossil Fuels-

  • These fuels are developed from fossils.
  • They are present in limited amount.
  • They are non-renewable sources of energy.
  • These fuels cause pollution. They release different oxides which causes acid rain which damages plants, animals, houses etc. Excessive release of carbon-dioxide also causes global warming.
  • Pollution by the fossil fuels can be controlled by increasing the efficiency of combustion process and using other techniques to escape the harmful gases.

Thermal Power Plants-

  • Thermal power plant is used to generate electricity using heat. Burning of fossil fuels produces the steam which is used to run the turbines. This method helps in efficient transmission of electricity.

Hydro Power Plants-

  • Use to convert potential energy of falling water into electricity. They are associated with dams. They do not cause any pollution. Dam construction also prevents flooding of rivers and also provide water for irrigation.
  • But there are certain disadvantages associated with hydro power plants. Large areas are needed for hydro power plants. Human settlement is affected as well as large ecosystems are destroyed.

Biomass

  • Biomass is the source of energy derived from living things (organic matter). For a long time, we relied on wood for the source of heat energy. In India, we make fuel out of biowaste such as cow dung due to the availability of a thriving population of livestock.
  • When wood is burnt in a limited supply of oxygen and water until volatile materials are removed, the residue left behind is charcoal. Charcoal has good heat generating efficiency. It also burns without flames.

Bio-gas plant-

  • In India cow dung, sewage waste, plant matter are decomposed in absence of oxygen to produce biogas. Since it has cow dung it is often termed as gobar gas.
  • A biogas plant is a dome-like structure built with bricks where cow dung and other biowaste are mixed with water to form a slurry and put into a digester.
  • The digester is a sealed chamber with anaerobic bacteria which breaks down the slurry.
  • This decomposition process releases gases like methane, CO2, hydrogen sulfide and hydrogen.
  • These gases are drawn via pipes which are transmitted to a turbine for the production of electricity.

Wind energy-

  • Environment-friendly efficient source of energy.
  • Wind is the natural phenomenon caused by pressure differentials due to unequal heating of land and water masses on the surface of the earth. It is harnessed in the form of kinetic energy.

Windmill-

  • Wind Energy is harnessed by rotatory structures known as windmills.
  • They have huge blades or fans attached very high on a rigid support that is attached to turbines that rotate due to high speeds of wind and generate electricity.
  • A single windmill has a low output and therefore, the wind farms are built that comprises of several windmills.

Solar energy-

  • Light energy and heat energy from the sun are known as solar energy.
  • Sun has been radiating energy from the past 5 billion years and will continue to do so at the same rate for another 5 billion years or more.
  • We must find ways to harness the energy with maximum efficiency, although only a small fraction of the solar energy reaches the earth’s surface.

Solar cell-

  • A device that converts solar energy into electricity is known as a solar cell.
  • A typical solar cell produces a voltage of 0.5 1 V and 0.7 W of electrical power. A large number of such cells can combine to form a solar panel which can generate power large enough for practical uses.
  • Advantages: (i) no moving parts (ii) require little maintenance (iii) can be set up in remote areas without the hassle and expenses of transmission lines.
  • Disadvantages: (i) Requires a special grade silicon which is not easily available (ii) Usage of silver for interconnections makes it expensive.
  • Uses: traffic signals, calculators, artificial satellites and space probes

Energy from sea-
The seas and oceans and other water bodies are a source of kinetic and potential energy due to the immense volume of water and the motion of waves.

Tidal energy-

  • Tides are variations in the level of water due to the gravitational pull of the moon.
  • The phenomenon of rise and fall of water level or high and low tide gives tidal energy.
  • Tidal energy is obtained by constructing dams near the narrow openings of the sea. When the tide sets in, it moves the turbine which directly produces electricity. It is limited to places near the sea.

Wave energy-

  • Waves possess a lot of kinetic energy that can be harnessed to produce electricity.
  • Waves are produced by strong winds blowing over the sea.
  • Limited to places with strong winds. Devices have been designed to capture this energy.

Ocean thermal energy-

  • The difference in surface temperatures of water and water at a certain depth in oceans is exploited to harness this form of energy.
  • Temperature difference must be 20∘ between the surface and water up to depths of 2 km.

Warm water is used to boil volatile ammonia to form vapours that move the turbine. Cold water is used to condense the vapour back to liquid.

Geothermal energy-

  • There is a huge amount of heat trapped inside the earth. Molten rocks from Earth’s core sometimes come up due to geological changes and get trapped in hotspots. Harnessing this heat energy is called geothermal energy.
  • Any underground water present gets heated due to the hotspots and gets converted to steam which escapes from the surface of the earth as hot springs.
  • This steam is used to rotate turbines and generate electricity.

Nuclear energy-

  • Nuclear energy can be used to generate electricity by means of nuclear fission.
  • In a nuclear reactor, the nuclear fuel is used to carry out sustained fission chain reaction to produce electricity at a controlled rate.

Nuclear fission
It is the process where a heavy atom (uranium or plutonium) is bombarded with neutrons that split the atom to give lighter nuclei. This process releases tremendous amounts of energy. For example, Fission of 1 atom of uranium gives 10 million times the energy of combustion of 1 atom of carbon from coal.

Disadvantages of using nuclear energy-

  • Nuclear waste is hazardous as heavy atoms decay into harmful subatomic particles.
  • High setup and maintenance cost
  • Limited availability of uranium
  • Can be used for destructive purposes

Nuclear fusion-

  • Fusion means combining lighter nuclei to produce a  heavier nucleus, usually hydrogen or hydrogen isotopes to create helium.
  • It releases a huge amount of energy. The mass deficit between the product and reactants are given by Einstein’s Equation. E = MC2

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