Coal and Petroleum Notes of class 8

Notes of NCERT Class 8th Sc. Chapter 5 – Coal and Petroleum

Q 1: What are natural resources?

A 1: Air, water, soil, sunlight, coal, petroleum, natural gas and minerals obtained from nature are called natural resources.

Q 2: Give examples of man-made materials.

A 2: Plastics, synthetic fibres, paints, drugs, explosives are all man made materials.

Q 3: Define resource.

A 3: Anything in the environment which can be used is called a resource.

Q 4: What are the types of natural resources?

A 4: All the natural resources can be classified into two main groups:

i). Inexhaustible natural resources – Cannot be used up completely and will continue to last forever. Examples are: Sunlight, Air and Water.

ii). Exhaustible natural resources – Resources which are present in a limited quantity in nature and can be exhausted by human activities. Examples are: Coal, Petroleum, Natural gas, Minerals, Forests and Wildlife etc.

Q 5: What are fossils?

A 5 : Fossils are the remains of the pre-historic plants or animals, buried under the Earth millions of years ago.

Q 6: What are fossil fuels?

A 6: The natural fuels formed from the remains of living organisms buried under the Earth long, long ago are called fossil fuels. Coal, Petroleum and natural gas are fossil fuels.

Q 7: How were fossil fuels formed?

A 7: Fossil fuels were formed from the dead remains of living organisms (plants and animals) buried under the Earth millions of years ago.

The plants and animals which died millions of years ago were gradually buried deep in the Earth and got covered with sediments like mud and sand, away from the reach of air. In the absence of air, the chemical effects of heat, pressure and bacteria, converted the buried remains of plants and animals into fossil fuels like coal, petroleum and natural gas.

Note: The buried remains of large land plants were converted into coal whereas those of tiny marine plants and animals were converted into petroleum and natural gas.

Q 8: What is coal and where is it found in India?

A 8: Coal is hard, black combustible mineral that consists mainly of carbon.

Coal is found in deep coal mines under the surface of the earth. In India, coal is found mainly in Bihar, West Bengal, Orissa and Madhya Pradesh.

Q 9: How coal was formed?

A 9: Coal was formed by the decomposition of large land plants and trees buried under the Earth about 300 million years ago.

About 300 million years ago, the Earth had dense forests in low-lying wet land areas. Due to natural processes like earthquakes, volcanoes and floods etc., these forests were buried under the surface of Earth. As more soil deposited over them, they were compressed. The temperature also rose as they sank deeper and deeper. Due to high pressure and high temperature inside the Earth and in the absence of air, the wood of buried forest plants and trees were slowly converted into coal.

Q 10: What is carbonisation?

A 10: The slow process by which the dead plants buried deep under the Earth have become coal is called carbonisation.

Q 11: What are the uses of coal?

A 11: The uses of coal are:

1. Used as a fuel in homes and industry.
2. Used as a fuel in Thermal Power Plants for generating electricity.
3. Used to make coal gas which is an important industrial fuel.
4. Used to make coke.
5. For making steam to run steam engines of trains.
6. As a source of organic chemicals.

Q 12: What are the products of coal?

A 12: The products of coal are Coal gas, Coal tar and Coke.

Q 13: What is coal gas and what are it uses?

A 13: Coal gas is a gaseous fuel which is obtained by the strong heating of coal in the absence of air during the processing of coal to get coke. Coal gas is mainly a mixture of methane and hydrogen with some carbon monoxide.

All the gases present on coal gas can burn to produce heat, due to which coal gas is an excellent fuel. Coal gas is used as a fuel in industries which are situated near the coal processing plants.

Nowadays, however, coal gas is used as a source of heat rather than light.

Q 14: What is Coal tar?

A 14: Coal tar is a thick, black liquid having an unpleasant smell which is obtained by heating coal in the absence of air. Coal tar is a mixture of about 200 carbon compounds. The useful carbon compounds present in coal tar include benzene, toluene, naphthalene, anthracene, phenol and aniline.

Q 15: What are the uses of products of coal tar?

A 15: The products of coal tar are used to make synthetic fibres, drugs (medicines), plastics, synthetic dyes, perfumes, paints, varnishes, pesticides, photographic materials, roofing materials and explosives etc.

Q 16: Which petroleum product is used these days for metalling the road surfaces?

A 16: Bitumen is used these days for metalling the road surfaces.

Q 17: What is coke and how is it prepared?

A 17: Coke is a tough porous black solid substance.

It is prepared by heating coal in the absence of air. When coal is heated in the absence of air, then coal gas and coal tar are eliminated, and coke is left behind as a black residue. Thus, coal minus volatile constituents is coke. Coke is an almost pure form of carbon. It is 98 per cent carbon.

Q 18: What are the uses of coke?

A 18:  The uses of coke are:

1. Used as a reducing agent in the extraction of metals like iron, zinc etc.
2. Used in the manufacture of steel.
3. Used as a fuel.

Q 19: Which is a better fuel – Coal or Coke?

A 19: Coke is a better fuel than coal because it produces more heat on burning than an equal amount of coal.

Q 20: Write in brief (5-10 sentences) about petroleum.

A 20: Petroleum is a dark coloured, thick crude oil found deep below the ground in certain areas. It has an unpleasant odour. The name ‘petroleum’ means ‘rock oil’ (petra = rock; oleum = oil). It is called petroleum because it is found under the crust of Earth trapped in rocks.

Petroleum is not a single compound but a complex mixture of compounds known as hydrocarbons. Hydrocarbons are compounds made up of only two elements – carbon and hydrogen.

Petroleum is insoluble in water. It is a natural resource obtained from deep oil wells which are dug in certain areas of the Earth. Just like coal, petroleum is also a fossil fuel. Petroleum is also called “crude oil” or “mineral oil”.

Q 21: How petroleum was formed?

A 21: Petroleum was formed by the decomposition of the remains of tiny plants and animals buried under the sea million of years ago. It is believed that millions of years ago, the tiny plants and animals which lived in the sea, died. Their dead bodies sank to the bottom of sea and were soon covered with mud and sand. Due to high pressure, heat and action of bacteria and in absence of air, the dead remains of tiny plants and animals were slowly converted into petroleum. The petroleum  thus formed got trapped between two layers of impervious rock (non porous rocks), forming an oil deposit.

Q 22: How petroleum is extracted?

A 22: Petroleum is extracted by drilling holes (called oil wells) in the Earth’s crust, where the presence of oil has been predicted by survey.

Q 22: Where was the first petroleum oil well drilled?

A 22: The first petroleum oil well was drilled in Pennsylvania (USA) in 1859.

Q 22: Where is petroleum found in India?

A 22: Petroleum is found in Assam, Gujarat, Mumbai High (off-shore area) and the near the basins of Godavari and Krishna rivers.

Q 23: What is petroleum refining and where is it done?

A 23: The process of separating crude petroleum (mixture) oil into more useful fractions is called refining.

The refining of petroleum is carried out in oil refinery.

Q 24: Which products are obtained from refining of petroleum?

A 24: The useful fractions obtained by the refining of petroleum are: Petroleum gas, Petrol, Kerosene, Diesel, Lubricating oil, Paraffin wax and Bitumen.

Q 25: Write uses of various fractions of Petroleum.

A 25: The following table shows the various uses of fractions of petroleum:

S.No.	Name of the fraction of Petroleum	Uses
1.	Petroleum Gas	Used as a fuel in homes and industry. Used as a fuel in the form of Liquefied Petroleum Gas (LPG).
2. 3.	Petrol Kerosene	Used as a fuel in light motor vehicles such as car, motorcycles and scooters etc. Used as a solvent for dry cleaning. Used as a fuel in wick stoves and pressure stoves to cook food. Is also used in lanterns for lighting purposes. A special grade of kerosene oil is used as aviation fuel in jet aeroplanes.
4.	Diesel	Used as a fuel in heavy motor vehicles such as buses, trucks and diesel train engines. Used to run pump sets for irrigation in agriculture and in electric generators to produce electricity on a small scale.
5.	Lubricating oil	Used for lubrication in machines and engines.
6.	Paraffin wax	Used for making candles, vaseline, ointments, wax paper and grease.
7.	Bitumen	Used for road surfacing. Used for water proofing the roofs of buildings. Used for making black paints.

Q 26: Are petroleum gas, petrol, kerosene and diesel fossil fuels?

A 26: Yes, petroleum gas, petrol, kerosene and diesel are fossil fuels as they are obtained from a major fossil fuel called petroleum.

Q 27: Which is the most common fuel used in homes?

A 27: The most common fuel used in homes is Liquefied Petroleum Gas (LPG). The gas used for domestic cooking is called liquefied petroleum gas because it is obtained from petroleum and it is liquefied by compression before filling into the gas cylinders.

Q 28: Why is Liquefied Petroleum Gas (LPG) a good fuel?

A 28: LPG is a good fuel because of its following advantages:

i). LPG burns easily

ii). LPG has a high calorific value. Due to this, a given amount of LPG produces a lot of heat.

iii). LPG burns with a smokeless flame and hence does not cause air pollution.

iv). LPG does not produce any poisonous gases on burning.

v). LPG does not leave behind any solid residue on burning.

Q 29: What does natural gas consist of?

A 29: Natural gas consists of methane with small quantities of ethane and propane.

Q 30: Is natural gas a fossil fuel?

A 30: Yes, natural gas is a fossil fuel.

Q 31: What is CNG?

A 31: CNG is Compressed Natural Gas which is obtained by applying pressure to the natural gas.

Q 32: What are the advantages of CNG?

A 32: The advantages of CNG are:

i). CNG burns easily and is a good fuel as it produces a lot of heat. Moreover, natural gas burns with a smokeless flame and causes no air pollution. It also does not produce any poisonous gases on burning. Natural gas does not leave any solid residue on burning. Natural gas is therefore a clean fuel as compared to fossil fuels.

ii). CNG is a complete fuel in itself and can be used directly for heating purposes in homes and industry. There is no need of adding anything to it.

iii). A great advantage of natural gas is that it can be supplied to homes and factories through a network of underground pipes and this eliminates the need for additional storage and transport.

Q 33: Where in India is the network of CNG pipes for its supply?

A 33: In India, the network of CNG pipelines is in Vadodara (in Gujarat), in some parts of Delhi and a few other places.

Q 34: What are the uses of Natural Gas or CNG?

A 34: The advantages of CNG are:

i). Used as a domestic and industrial fuel.

ii). Used as a fuel in Thermal Power Stations for generating electricity.

iii). Used as a fuel in transport vehicles like cars, buses etc. in place of petrol and diesel. CNG is a cleaner fuel and does not cause much air pollution.

iv). Used as a source of hydrogen gas needed to manufacture fertilisers.

v). Used as a starting material for the manufacture of a number of chemicals which are called petrochemicals.

Q 35: What are petrochemicals? Give examples.

A 35: Chemicals obtained from petroleum and natural gas are called petrochemicals. Some examples are: methyl alcohol, ethyl alcohol, formaldehyde, acetone, acetic acid, ethylene, benzene, vinyl chloride and hydrogen.

Q 36: What are the uses of petrochemicals? 

A 36: Petrochemicals are very important because they are used to manufacture a wide range of useful materials such as : Detergents, Synthetic fibres (like Polyster, Nylon, Acrylic etc.), Plastics (such as Polythene, Polyvinyl chloride, Bakelite etc.),  Synthetic rubber, Drugs, Dyes, Perfumes, Fertilisers, Insecticides and Explosives etc.

Q 37: Which is other name for petroleum?

A 37: Black gold is the other name for petroleum.

Q 38: For how much time approximately fossil fuels will last?

A 38: The amount of coal, petroleum and natural gas in the Earth is limited. The known reserves of coal, petroleum and natural gas will last only for about 100 years.

Q 39: Why should we use fossil fuels only when absolutely necessary?

A 39: We should use fossil fuels only when absolutely necessary because:

i). It will ensure the availability of fossil fuels for a longer period of time.

ii). It will reduce air pollution and lead to a cleaner environment.

iii). It will reduce the risk of global warming.

Q 40: Can fossil fuels such as coal, petroleum and natural gas be prepared in the laboratory?

A 40: No, fossil fuels such as coal, petroleum and natural gas cannot be prepared in the laboratory from dead organisms (dead plants and animals). This is because the formation of fossil fuels is a very, very slow process and the conditions for their formation cannot be created in the laboratory.

Q 41: What is the full form of PCRA?

A 41: PCRA stands for Petroleum Conservation Research Association.

Q 42: What tips should be followed for minimising the wastage of petrol and diesel while driving vehicles?

A 42: Following tips should be followed for saving petrol and diesel while driving vehicles:

i). Drive the vehicle at a constant and moderate speed as far as possible.

ii). Switch off the vehicle’s engine at traffic lights or at a place where the wait time is more than two minutes.

iii). Ensure correct air pressure in the tyres of the vehicle. Low tyre pressure consumes more fuel.

iv). Ensure regular maintenance of the vehicle including engine tuning.