CBSE Class 8 Social Science Minerals And Energy Resources Notes

CBSE Class 8 Social Science Minerals and Energy Resources Notes Learning the important concepts is very important for every student to get better marks in examinations. The concepts should be clear which will help in faster learning. The attached concepts made as per NCERT and CBSE pattern will help the student to understand the chapter and score better marks in the examinations.

MINERALS AND ENERGY RESOURCES

IMPORTANT TERMS AND CONCEPTS

• Minerals Natural inorganic substances, which consist of one or more elements.

• Ductility : It is the ability of a metal to be drawn into thin wire without breaking.

• Smelting : The process of separating of metals from their ores by the use of heat.

• Mining : Extracting commercially valuable minerals from the earth.

• Quarrying : Mining of ores from the surface of the land.

• Shaft Mining : Mining of ores at great depths below the ground.

• Open Cast Mining : Mining of ores from shallow depth by removing the overlying rocks.

• Recycling : Using discarded materials once again.

• Mineral Fuels (fossil) : Non-metallic minerals used as power resources or fuel such as coal and petroleum.

• Drilling : The process of digging wells and extracting mineral oil.

• Grid : Transmission of electricity through network of power lines.

• Fossils : Decomposed marine creatures, minute plants, and animals buried and sedimented millions of years ago.

• Reservoir Rocks : The rocks that contain large deposits of oil and gas.

• Rock : Exposed hard substance of the lithosphere is known as the rock. It consists of one or more minerals but with no definite mineral composition.

• Metallic Minerals : Metallic minerals contain metals and are good conductors of heat and electricity.

Metals have the characteristics of shine and lustre.

• Non-Metallic Minerals : Non-metallic minerals do not contain metals and are bad conductors of heat and electricity. Non-metals lack shine and lustre.

• Robber Industry : The extraction of mineral resources from the earth is called ‘Robber Industry’. It is called so because indirectly the planet is getting robbed of its mineral resources.

• Conventional Sources : Conventional sources of energy are those sources which have been in use for quite sometime and got exhausted. For example–coal, petroleum, natural gas, etc.

• Non-Conventional Sources of Energy : Non-conventional sources of energy are replenishable in nature. They are a result of progress in the field of science and technology. Solar, wind tidal, geo-thermal energy are the examples of non-conventional sources of energy

• Black Gold : Petroleum and its derivatives are called Black Gold.

• CNG : It signifies Compressed Natural Gas. It is Eco-friendly automobile fuel. It causes less pollution.

• Biogas : It is a fuel for cooking and lighting obtained from organic waste of dead plants and animal material.

Fact File

* Salt and graphite are also treated as minerals.
* All rock minerals are rocks but all rocks are not minerals.
* Sometimes rock looks blue because its contains copper minerals. There is no well known minerals in Switzerland.
* The rarest available diamond is the green diamond.
* Petroleum is the combination of two Latin words
* Petra means – Rock and
* Oleum means – Oil.
* The first country to develop hydroelectricity was Norway.
* Scotland is the site of the first world’s solar and wind powered bus shelter.

Mineral : A naturally occuring substance that has a definite chemical compocition is called Mineral.

Importance of Minerals :

• Mineral are not evenly distributed

• Some minerals are formed in area which are not earily accessible such that the Artic Ocean bed and Antarctica.

• Mineral can be identified on its basis of their physical properties such as colour, density, hardness, and chemical properly.

CLASSIFICATION OF MINERALS

• Metallic Minerals : We get metals from these minerals metallic minerals further be divided into ferrous and non-ferrous.

(i) Ferrous minerals : The minerals which contain Iron ore are called ferrous minerals. e.g. Iron Ore, Nickel, Cobalt etc.

(ii) Non Ferrous : Minerals containing metals other than iron ore are known as non-ferrous minerals. Gold, Silver, Platinum etc.

(iii) Precious Mineral : The minerals which have very high economic value are known as Precious minerals e.g. Gold, Silver etc.

(iv) Energy Minerals : The minerals which provide energy or power are known as energy minerals. e.g. Coal, Petroleum, Natural gas etc.

1. Mining : The process of taking out minerals from rocks buried under the earth surface is called mining.

• Open Cast Mining :- Mineral that lies at shallow depths are taken out by removing the surface layer. This is open Cast Mining.

• Shaft Mining :- Extraction of Minerals from deep bores i.e. shaft of deep depth is called shaft mining.

2. Drilling : The process of digging wells and extracting mineral oil is known as 'drilling'. In this deep wells are dug for extracting oil and natural gas.

3. Quarrying : It is the process used to extract mineral that lie near the surface. In this an open pit is dug. Such an open pit mine is called a 'quarry'.

FERROUS MINERALS

• Iron Ore :
(i) Iron ore is the basic minerals.
(ii) India is rich in good quality iron ores.
(iii) Magnetite : This is the best quality of iron ore and contains about 72% iron. It has excellent magnetic qualities, especially valuable in the electrical industry.
(iv) Hematite : It is most important industrial iron ore in terms of quantity used. It contains 60% to 70% of pure Iron.
(v) The major iron ore belts in India are :

MANGANESE

• Uses : (i) It is mainly used in the manufacturing of steel and ferro-mangnese alloy.
(ii) It is also used in manufacturing bleaching powder, insecticides and paints.
(iii) It increases the strength of steel.
(iv) It is also used for making glass and chemical.

• Importance :
(i) India is one of the leading producer of Manganese.
(ii) Manganese of India is of high quality and is in great demand.
(iii) Japan is the leading importer of India's Manganese. 

• Production: Maharashtra, M.P., Orissa, Karnataka and Andhra Pradesh.

COPPER

• Properties :
(i) The physical properties of copper make it valuable to industry.
(ii) Being malleable, ductile and a good conductor, It is mainly used in electrical cables, electronics and chemical industry.
(iii) India is critically deficient in the reserve and production of Copper.

• Uses :
(i) It is useful in cooking utensils, radiation and refrigerators.
(ii) It is used in ranging from rain gauges to electronic system for rockets.
(iii) Large amount of Copper wires are used in various kind of electrical equipment. 

• Production : Orissa, Gujarat, Maharashtra

BAUXITE

Bauxite is the main ore of aluminium. Bauxite deposits are formed by the decomposition of rock rich in aluminium silicates.

• Uses :
(i) It is a good conductor of heat and electricity.
(ii) It is used to make cans for various beverages.
(iii) It can be pressed into a thin foil.
(iv) Because it is light and strong, it is used in space craft.
(v) The bodies and parts of some automobilies are made from aluminium alloy.

• Production :
(i) Orissa – 45%
(ii) Gujarat – 17%
(iii) Jharkhand – 14%
(iv) Maharashtra – 11%
(v) Other – 13% (Chattisgarh etc.) 

India is the largest producer of bauxite in South Asia.

NON-METALLIC-MINERALS

• Mica :
It is a non metallic mineral. India is the largest producer of mica and it produces more than 60% word's mica.

• Main Properties and Uses of Mica :
(i) It is made up of a series of plates or leaves.
(ii) It can be converted into thin sheets.
(iii) It can be black, green, red yellow or brown.
(iv) It has excellent di-electric strength, low powerless factor, insulating properties and high resistance.
(v) It is indispensable minerals used in electric and electronic industries.

• Production : 

Northern edge : Chotta Nagpur Plateau Koderma Gaya-Hazaribagh belt of Jharkhand.
Rajasthan : Ajmer
Andhra Pradesh : Nellore Mica belt.

ROCK MINERALS

• Lime stone :
Uses and Properties
(i) It is associated with rocks composed of either calcium carbonate of magnesium, or mixture of these two.
(ii) It is found in sedimentary rocks.
(iii) It is used for variety of purposes.
(iv) It is a basic input in cement Industry.
(v) It is also used by chemical, iron and steel industry.

• Distrubition : 

Madhya Pradesh, Andhra Pradesh, Rajasthan, Tamil Nadu and Gujarat.

CONSERVATION OF MINERALS

Minerals are considered back bone of of an economy. Most of the mineral are non-renewable. So there is urger need to conserve them.

• Measures to conserve the minerals :
(i) Minerals should be used in a planned and judicious way.
(ii) Wastage of minerals should be minimised.
(iii) Modern technology should be used for the exploitation of minerals.
(iv) Export of minerals should be minimised.
(v) We should think about the use of substitutes in order to save minerals.
(vi) We should encourage recycling of metals.

ENERGY RESOURCES

• Energy resources : The resources which are used for generating energy are known as energy resources e.g. Coal, Petrolem etc.

CLASSIFICATION OF ENERGY RESOURCES

• Conventionial Resource : Conventional power resources are those which are exhautible.
(i) Once they have been used up, they cannot be replaced e.g. coal, petrolem
(ii) They are very costly and causes pollution.
(iii) These are going to last just for 100 – 200 years.
(iv) These are non-renewable source of energy e.g. coal, petrolem, uranium.

• Non-Conventional Resource : There are resources of energy which can be renewed in a short period.
(i) They are known as renewable resources.
(ii) They are free of cost.
(iii) They do not cause any pollution.
(iv) They are going to last forever.
(v) e.g. wind, water, solar energy, geothermal energy.

CONVENTIONAL SOURCES OF ENERGY

• Coal :
(i) Coal provides a substantial part of the Nation's energy need. It is used for power generation.
(ii) India is highly dependent on coal for meeting its commerical energy requirements.
(iii) Coal is formed due to compression of plant material over million of years.
(iv) Coal is formed in a variety of forms depending on the degrees of compression and the depth and time of burial.

• Varieities of Coal and its availability :

1. Anthracite Coal :
(i) This is the best quality of Coal and contain over 80% carbon.
(ii) It is very hard, compact jet black Coal having a semi metallic lustre.
(iii) It has the highest heating value and burns without smoke or root, which make it suitable for domestic use.
(iv) It is found only in Jammu Kashmir and that too is small quantity.

2. Bituminous coal :
(i) This is the most widely used coal and contain 60 to 80% carbon.
(ii) It is dense, compact, bittle and is usually of black colour.
(iii) It has the highest heating value and burns without smoke or root, which make it suitable for domestic use.
(iv) It is found only in Jammu Kashmir and that too in small quantity.

3. Lignite :
(i) This is the most widely used coal and conbtain 60 to 80% carbon.
(ii) Lignite is a lower grade coal which is soft with high moisture content and contain about 60% carbon
(iii) Its colour varies from dark to black brown.
(iv) It is found in Plana of Rajasthan, Naveli of Tamil Nadu, Hakhimpur of Assam and Karewa of Jammu & Kashmir.

4. Peat :
(i) This is the first state of transformation of wood into coal.
(ii) It contains 50-60% carbon.
(iii) It burns like wood, gives less heat, emits more smoke and leaves a log of ash after burning.

• Classification of Coal field in India :

Gondwana Coal Field :
Gondwana coal is over 200 millions years in age gondwana coal metallurgical coal is located in Damodar valley (Weat Bengal Jharkhand). Jharia, Raniganj, Bokaro, Godavari, Mahanadi, Son and Wardha Valleys.

Tertiary Coal Field :
The Tertiary rock system bears coals of younger age which are only about 55 million years old and are minaly confined to the extre peninsula. Important area of tertiary coal include parts of Assam Meghalaya, Arunchal Pradesh, Nagaland.

PETROLEUM

The word 'petroleum' has been derived from two Latin words, Petra (meaning rock) and oleum (meaning oil).Thus petrolem is oil obtained from rocks, particularly sedimentary rocks of the earth. Therefore, its also called mineral oil. Petroleum is an inflamble liquid that is composed of hydrocarbons.

• Use of Petroleum :
(i) It is the major source of power for vehicles.
(ii) It provides the most important lubricating agents and is used as important raw material.
(iii) Petroleum refineries act as a 'nodel industry' for many industries like textile, fertilizer and chemical industry.

• Formation :
(i) In regions of folding, anticlines or dams, oil is trpped in the crest of the upfold.
(ii) Gas, being lighter usually occurs above the oil.
(iii) 63% of India's petroleum production is from Mumbai high, 18% from Gujarat and 16% from Assam.
(iv) Ankeleshwar is the most important field of Gujarat. Assam is the oldest oil producing state of India.

NATURAL GAS

• Advantages of Natural gas :
(i) It can be used both as source of energy and also as a industrial raw material in petro-chemical industry.
(ii) Natural gas is found in association with or without petroleum.
(iii) It takes less time to built a power plant based on natural gas.
(iv) It is easy to transport gas through gas pipes line.
(v) It is considered an environment friendly fuel because of low carbondioxide emission.
(vi) It is the fuel for the present century.

• Gas pipe lines :
1700km long Hazira-Bijapur-Jagdishur cross country gas pipe line links mumbai-high and Bassin with fertilizer, power and industrial complex in Western and Northern India.

ELECTRICITY

Electricity is generated mainly in two ways
(i) By running water which drives hydro turbines to generate hydro electricity.
(ii) By burning of other fuels such as coal, petroleum and natural gas to drives turbines to produce thermal power.

1. Hydro Electricity :
(i) It is generated by fast flowing water.
(ii) It is a renewable resource of energy.
(iii) India has a number of multi puopose project like the Bhakra Nangala, Damodar Valley Corporation, the Kopili Hydel Power Porject etc. Producing hydro electricity.
(iv) These do not cause any pollution.
(v) These should be near the sources of energy.

2. Thermal Power :
(i) It is generated by coal, petroleum and natural gas.
(ii) These are exhaustible resources of energy.
(iii) These causes pollution.
(iv) These can be set at any place.

3. Nuclear or Atomic Energy :
(i) It is obtaining by altering the structure of atoms energy is released in the form of heat and his is used to generate electric power.
(ii) Uranium and Thorium, which are available in Jharkhand and the Aravali ranges of Rajasthan are used for nuclear power.
(iii) The monazite sand of Kerala is also rich in Thorium.
(iv) It has vest potential for furture development.
(v) It is very economical.

NON-CONVENTIONAL ENERGY SOURCES.

(i) These are non exhaustible.
(ii) They are renewable sources of energy.
(iii) They do not cause environment pollution and are freely available.
(iv) They energy resources are in great demand but production of fossil fuels is limited so non conventional sources of energy are hope of the furture.

• Solar Energy :
(i) Photovolaic technology converts sunlight directly into electricity.
(ii) It is expected that solar energy plant will be able to minimise the dependence of rural households on firewoods and dung cake, which is turn will contribute to environmental conservation and adequate supply of manure in agriculture.
(iii) The largest solar plant of India is located at Madhopur, near Bhuj, to sterilise milk cans.

• Wind Power :
(i) India now ranks as a 'wind super power' in the world.
(ii) The cost inputs are only at the initial stage and the power generation starts immediately after commissioning.
(iii) Once the generation starts, cost free power is available for about 20 years.
(iv) The largest wind forms cluster is located in Tamil Nadu from Nagarcoil to Madurai. Apart from these andhra Pradesh, Karnataka, Gujrat, Kerala, Maharashtra and Lakshdweep have important wind farms.

• Biogas :
(i) Shrubs, farms waste, animal and human waste are used to produce biogas.
(ii) Decomposition of organic matter yields gas, which has higher thermal efficiency in comparison to kerosene dung cake and charcoal.
(iii) Biogas plant are setup at municipal, cooperative and individual level.
(v) The plants using cattle dung are known as 'Gobar gas plant'. These provide twin benefits to the farmers in the form of energy and improved quality of manure.
(vi) It burns wit5hout smoke cheapest gaseous fuel.

• Tidal Energy :
Oceanic tides can be used to generate electricity. Flood gate dams are built across the inlets. During high tide water flows into the inlet and gets trapped when the gate is closed. After the tides falls our side the flood gate, teh water retained by the food gate flows back to the sea via a pipe that carries it through a power generating turbine. In India, the Gulf of kucch, provides ideal conditions for utilising tidal energy.
Two experimental project have been set up in India one is located in te Parvati Valley near Manikaram in Himachal Pradesh and the other is in the Puga Valley, Ladakh.

CONSERVATION OF ENERGY RESOURCES

Energy is the basic requirement for economic development. Consumption of energy in all forms has been steadily rising all over the country.
There is an urgent need to develop a sustainable path of energy development. Promotion of energy conservation and increased use of renewable energy sources are the twin planks of sustainable energy.We have to adopt a cautious approach for the judicious use of our limited energy resources.

MINERALS AND POWAR RESOURCES 

Q1. Define mineral. Give example also.

A1. Mineral- A naturally occurring substance that has a definite chemical composition is a mineral ex iron, diamond and petroleum etc.

Q2. How minerals are formed?

A2. Minerals are formed in different types of geological environments, under varying conditions. They are created by natural processes without any human interference.

Q3. Classify minerals on the basis of composition?

A3. On the basis of composition minerals can be classified into metallic and non metallic minerals.

Q4. What is the importance of power resource ?

A4. Power or energy plays a vital role in our lives. We also need power for industry, agriculture, transport, communication and defense.

Q5. How fossil fuels are formed ?

A5. Remains of plants and animals which were buried under the earth for millions of years got converted by the heat and pressure into fossil fuels.

Q6. Why coal is referred to as buried sunshine ?

A6. Coal is referred to as buried sunshine because of the following reasons :-

1) It produces energy.

2) It is buried under the layers of the earth.

Q7. What is thermal power ?

A7. This is the most abundantly found fossil fuel. It is used as a domestic fuel, in industries such as iron and steel, steam engines and to generate electricity. Electricity from coal is called thermal power.

Q8. Name the leading producer of coal in the world and India ?

A8. The leading coal producers of the world are China, USA, Germany, Russia, South Africa and France. The coal producing areas of India are Raniganj, Jharia, Dhanbad and Bokaro in Jharkhand.

Q9. Where petroleum is found ?

A9. It is found between the layers of rocks and is drilled from oil fields located in off-shore and coastal areas.

Q10. What are the by products of petroleum ?

A10. The byproducts of petroleum are diesel, petrol , kerosene, wax, plastic And lubricants.

Q11. Why petroleum is referred to as black gold ?

A11. Petroleum is referred to as black because:-

1) Its derivatives like diesel, kerosene and petrol are very expensive.

2) It is black in colour when drilled.

Q12. Name the petroleum producing countries ?

A12. The chief petroleum producing countries are Iran, Iraq, Saudi Arabia and Qatar. The other major producers are USA, Russia, Venezuela ,Algeria and India.

Q13. Name the leading producers of petroleum in India ?

A13. The leading producers in India are Digboi in Assam, Bombay High in Mumbai and the deltas of Krishna and Godavari rivers.

Q14. Where natural gas is found and what are its uses ? Name the two types of natural gas?

A14. Natural gas is found with petroleum deposits and is released when crude oil is brought to the surface.

It can be used as a domestic and industrial fuel. The two types of natural gas are:-

1) LPG- Liquified petroleum gas.used in cooking gas etc.

2)CNG- Compressed natural gas used in running vehicles.

Q15. Name the producers of Natural gas in the world and India ?

A15. Russia, Norway, UK and the Netherlands are the major producers of natural gasin the world. In India Jaisalmer, Krishna Godavari delta, Tripura and some areas off shore in Mumbai have natural gas resources.

Q16. How hydro electricity is produced ?

A16. Rain water or river water stored in dams is made to fall from heights. The falling water flows through pipes inside the dam over turbine blades placed at the bottom of the dam. The moving blades then turn the generator to produce electricity. This is called hydro electricity.

Q17. Name the leading producers of hydel power in the world and India ?

A17. The leading producers of hydel power in the world are Paraguay, Norway, Brazil, and China. Some important hydel power stations in India are BhakraNangal, Gandhi Sagar, Nagarjunsagar and Damodar valley projects.

Q18. What are the uses of Wind mill ?

A18. Wind mills have been used for grinding grain and lifting water since times immemorial. In modern time wind mills, the high speed winds rotate the wind mill which is connected to a generator to produce electricity.

Q19. What is Wind farm and where it is located ?

A19. Wind farms having clusters of wind mills are located in coastal regions and in mountain passes where strong and steady winds blow. Wind farms are found in Netherlands, Germany, Denmark, UK, USA and Spain are noted for their wind energy production.

Q20. How is nuclear power obtained ?

A20. Nuclear power is obtained from energy stored in the nuclei of atoms of naturally occurring radio active elements like uranium and thorium. These fuels undergo nuclear fission in nuclear reactors and emit power.

Q21. Name the producers of Nuclear power in the world and India ?

A21. The greatest producers of nuclear power are USA and Europe. In India Rajasthan and Jharkhand have large deposits of Uranium. Thorium is found in large quantities in the Monozite sands of Kerala.

Q22. Name the nuclear power stations in India ?

A22. The nuclear power stations in Indiaare located in Kalpakkam in Tamilnadu, Tarapur in Maharastra, RanapratapSagar near Kota in Rajasthan, Narora in Uttar Pradesh and Kaiga in Karnataka.

Q23. What is Geo-thermal energy ?

A23. Heat energy obtained from the earth is called geothermal energy.

Q24. How Geo-thermal energy is produced ?

A24. The temperature in the interior of the earth rises steadily as we go deeper. Some times this heat energy may surface itself in the form of hot springs. This heat energy can be used to generate power.

Q25. What are the different uses of Geo-thermal energy ?

A25. Geothermal energy in the form of hot springs has been used for cooking, heating and bathing for several years.

Q26. Name the largest Geo-thermal power plants in the world and India ?

A26. USA has the world’s largest geothermal power plants followed by New Zealand, Iceland, Philippines and Central America. In India, geothermal plants are located in Manikaran in Himachal Pradesh and PugaValley in Ladakh.

Q27. What is tidal energy and how it is harnessed ?

A27. Energy generated from tides is called tidal energy. Tidal energy can be harnessed by building dams at narrow openings of the sea. During high tide the energy of the tides is used to turn the turbine installed in the dam to produce electricity.

Q28. Where tidal mill farm are found ?

A28. Russia, France and the Gulf of Kachchh in India have huge tidal mill farms.

Q29. What is Bio-gas ?

A29. Organic waste such as dead plant and animal material, animal dung and kitchen waste can be converted into a gaseous fuel called biogas.

Q30. What are different uses of solar energy ?

A30. Solar energy is also used in solar heaters, solar cookers, solar dryers besides being used for community lighting and traffic signals.

Q31. What are the uses of Bio-gas ?

A31. Biogas is an excellent fuel for cooking and lighting and produces huge amount of organic manure each year.

Q32. How energy can be conserved ?

A32 Energy can be conserved by the following way :-

1) Using energy resources rationally and judiciously.

2) Energy saved is energy generated.

Q33. How minerals can be conserved ?

A33. Minerals can be conserved by the following ways :-

1) Reduce wastage in the process of mining.

2) Recycling of metals.

3) Export of minerals should be minimum.

4) To save the minerals their substitute should be used.

3 R – Reuse, reduce and recycle

Q34. Differentiate between :-

1) Ferrous and non –ferrous minerals.

2) Metallic and non metallic minerals.

Q35. Explain the methods by which minerals are extracted ?

A35. The process of taking out minerals from rocks buried under the earth’s surface is called mining.

There are various ways of extracting minerals, it as follows:-

1) Minerals that lie at shallow depths are taken out by removing the surface layer; this is known as open-cast mining.

2) Deep bores, called shafts, have to be made to reach mineral deposits that lie at great depths. This is called shaft mining.

3) Petroleum and natural gas occur far below the earth’s surface. Deep wells are bored to take them out, this is called drilling

4) Minerals that lie near the surface are simply dugout, by the process known as quarrying.

Q36. Explain the distribution of minerals?

A36. Minerals occur in different types of rocks. Some are found in igneous rocks, some in metamorphic rocks while others occur in sedimentary rocks.

Generally, metallic minerals are found in igneous and metamorphic rock formations that form large plateaus. Iron-ore in north Sweden, copper and nickel deposits in Ontario ,Canada, iron, nickel, chromites and platinum in South Africa are examples of minerals found in igneous and metamorphic rocks.

Sedimentary rock formations of plains and young fold mountains contain non- metallic minerals like limestone

Q37. Complete the following table showing the distribution of minerals in the World:

Q38. Complete the following table showing distribution of minerals in India.

Q39. List the uses of minerals?

A39. 1) Iron ore is used for manufacturing of machines, agriculture implements and items of general use.

2) Minerals which are used for gems are usually hard. These are then set in various styles for jewellery.

3) Copper is another metal used in everything from coins to pipes.

4) Silicon, used in the computer industry is obtained from quartz.

5) Aluminum obtained from its ore bauxite is used in automobiles and airplanes, bottling industry, buildings and even in kitchen cookware.

6) Mica is used in electrical and electronic industries.

7) Manganese ore is used for making iron, steel and preparing alloys.

Q40. Differentiate between conventional and non-conventional sources of energy ?

Q41. List the advantages and disadvantages of the following non-conventional sources of energy :-

1) Wind energy.

2) Solar energy.

3) Tidal energy.

4) Nuclear energy.

5) Bio gas.

6) Geo thermal energy.

A41.

Q42. Differentiate between Natural gas and Biogas.

A42