These NCERT Solutions for Class 8 Science Chapter 5 Coal and Petroleum Questions and Answers are prepared by our highly skilled subject experts to help students while preparing for their exams.
Coal and Petroleum NCERT Solutions for Class 8 Science Chapter 5
Class 8 Science Chapter 5 Coal and Petroleum Textbook Exercise Questions and Answers
What are the advantages of using CNG and LPG as fuels?
Following are the advantages of using CNG and LPG as fuels:
- CNG and LPG are the cleanest of all the fossil fuels. They do not leave behind any residue on burning.
- Compressed Natural Gas (CNG) and LPG are less polluting and non-corrosive which can be used for burning.
- Calorific value of these fuels is very high. Hence they are used for cooking purposes.
Name the petroleum product used for surfacing of roads.
These days bitumen, a petroleum product, is used for surfacing the roads in place of coal tar.
Describe how coal is formed from dead vegetation. What is this process called?
Millions of years ago, dense forests and animals got buried under the soil due to natural processes like floods, earthquakes and thunderstorms. When they got buried deep in the soil, they were exposed to very high pressure and temperature. Under these conditions, these slowly got converted into coal. This process of formation of coal is called carbonisation.
Fill in the blanks:
a. Fossil fuels are ………………, ……………… and ………………
b. Process of separation of different constituents from petroleum is called ………………,
c. The least polluting fuel for vehicle is ………………,
a. coal, petroleum, natural gas,
Tick True/False against the following statements:
a. Fossil fuels can be made in the laboratory. (T/F)
b. CNG is more polluting fuel than petrol. (T/F)
c. Coke is almost pure form of carbon. (T/F)
d. Coal tar is a mixture of various substances. (T/F)
e. Kerosene is not a fossil fuel. (T/F)
Explain why fossil fuels are exhaustible natural resources.
Fossil fuels require millions of years to form from the dead vegetation and animals that got buried deep inside the earth. They require high temperature and pressure for their formation, which cannot be provided in the laboratory. Thus, fossils are limited. Therefore, the use of fossil fuels at this rate will lead to their exhaustion. Since, the time taken for the formation of fossil fuels is much higher than the human life span, they are considered as exhaustible natural resources.
Describe characteristics and uses of coke.
Coke is a type of coal. It is a tough, porous and black substance. It is almost pure form of carbon. Coke is much cleaner than coal and provides more energy on burning. It is used in the manufacture of steel and in the extraction of many minerals.
Explain the process of formation of petroleum.
Petroleum is a dark, oily and thick liquid. It is a mixture of various fractions. Petroleum was formed by the decomposition of the remains of tiny plants and animals under the sea. 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, action of bacteria and in the absence of air. the dead remains of tiny plants and animals were slowly converted into petroleum. The petroleum thus formed got trapped between the two layers of impervious rock, forming an oil deposit.
The more volatile component of petroleum formed a gaseous cover over petroleum. Such a gaseous mixture covering the crude oil is known as natural gas.
The following table shows the total power shortage in India from 1991-1997. Show the data in the form of a graph. Plot shortage percentage for the years on the Y-axis and the year on the X-axis.
|S. No.||Year||Shortage (%)|
Scale: Along X-axis: 1 unit = 1 year
Along Y-axis: 1 unit = 1%
NCERT Extended Learning Activities and Projects
Get an outline map of India. Mark the places in the map where coal, petroleum and natural gas are found. Show the places where petroleum refineries are situated.
Do it yourself.
Choose any five families of your neighbourhood. Enquire whether their energy consumption (coal, gas, electricity, petrol, kerosene) has increased or decreased in the last five years. Enquire also about the measures they adopt to conserve energy.
Do it yourself.
Find out the location of major thermal power plants in India. What could be the reasons for their being located at those places?
Do it yourself.
Objective: To classify the resources as natural or man-made.
Materials Required: Pen and paper.
- Observe your surroundings and make a list of various materials used by us in daily life.
- Classify these materials as natural or man-made in a table as shown below.
Conclusion: Natural resources like air, water, sunlight, etc., are present in nature while man-made resources like building, roads, plastics, etc., are synthesised by humans.
Fossil Fuels: Dead remains of organisms (plants or animals) which are more than 10,000 years old are called fossils. The fuels which are formed by the decomposition of fossils over millions of years are called fossil fuels, e.g., coal and petroleum.
Coal: Coal is a hard, black, combustible mineral that consists mainly of carbon. It is formed by the deeply buried remains of vegetation under high pressure and high temperature over millions of years. Since coal contains mainly carbon, the slow process of conversion of dead vegetation into coal is called carbonisation.
Uses of Coal: Coal bums in air to produce heat and carbon dioxide. Coal is used as a fuel because it provides large amount of heat energy.
C + O2 → CO2
- Coal was used as a fuel in steam engines.
- Most of the thermal power plants still use coal as a fuel.
- Coal is still being used as a kitchen fuel in some households, dhabas and restaurants.
- Many useful products, like coke, coal-tar and coal gas, are made by processing coal.
Destructive distillation: When any substance is heated in the absence of air to form a number of different products, the process is known as destructive distillation. The products which are obtained by the process of destructive distillation of coal are coke, coal tar and coal gas.
i. Coke: Coke is an almost pure form of carbon, is tough, porous and black. Coke is used in the manufacture of steel and extraction of many metals.
ii. Coal Tar: It is a black thick liquid with an unpleasant smell. Coal tar is a mixture of about 200 substances. It is used as a raw material for making various items like synthetic dyes, drugs, explosives, perfumes, plastics, paints, photographic materials, roofing materials, naphthalene balls, etc. It is used for making the surface of roads. Bitumen (a petroleum product) has almost replaced coal tar for making road surfaces.
iii. Coal Gas: Coal gas is produced during the processing of coke from coal. Coal gas is used as a fuel in many industries which are situated near coal mines.
Petroleum: Petroleum is a dark oily liquid and has a foul smell. It contains many constituents like petroleum gas, petrol, diesel, lubricating oil, paraffin wax, etc.
Formation of Petroleum: Petroleum was formed from the organisms living in the seas. When these organisms died, their bodies got settled at the bottom of the sea and eventually, layers of sand and clay got deposited over them. After millions of years in the absence of air, the high temperature and high pressure converted them into petroleum and natural gas. Today, we drill down through layers of sand, silt and rock to reach the rock formation that contains oil and natural gas deposits.
Refining of Petroleum: It is the process of separating the various constituents of petroleum and is carried out in a petroleum refinery. The various constituents of petroleum and their uses are as follows:
Various Constituents of Petroleum and their Uses
|Constituents of Petroleum||
|1.||Liquefied Petroleum Gas (LPG)||Fuel for home and industry|
|2.||Petrol||Motor fuel, aviation fuel, solvent for dry cleaning|
|3.||Kerosene||Fuel for stoves, lamps and for jet aircrafts|
|4.||Diesel||Fuel for heavy motor vehicles, electric generators|
|6.||Paraffin wax||Ointments, candles, vaseline, etc.|
|7.||Bitumen||Paints, road surfacing|
Natural Gas: Natural gas is considered important as this fossil fuel can easily be transported through pipes. It is stored as CNG (compressed natural gas) which is used for several purposes and is also used as a starting material for manufacturing many chemicals and fertilisers. Natural gas does not cause pollution and has a high calorific value.
Limitations of Natural Resources: Fossil fuels like coal, petroleum, etc., need millions of years to get transformed from dead bodies into fuels. But currently, their demands are so high that after a few hundred years there will be a scarcity of these resources. In addition, too much of air pollution is caused when these fuels are burnt. These fuels are also responsible for the problems associated with the global warming. Hence, it is very important to use these fuels wisely.
Some of the PCRA (Petroleum Conservation Research Association) recommendations for the conservation of petrol and diesel are as follows:
- Drive at constant and moderate speed as far as possible.
- Switch off the engine at traffic lights or at a places where you have to wait.
- Ensure correct tyre pressure.
- Ensure regular maintenance of the vehicle.
Class 8 Science Chapter 5 Coal and Petroleum Additional Important Questions and Answers
Very Short Answer Type Questions
What is a natural resource?
A resource which is obtained from nature is called a natural resource.
What do you mean by inexhaustible natural resources?
The resources which are available in huge quantity and cannot be exhausted by human activities are called inexhaustible natural resources, e.g. sunlight, air, water, etc.
What is an exhaustible natural resource?
A resource which is available in limited quantity and can be exhausted by human activities is called exhaustible natural resource, e.g., coal, petroleum, natural gas, etc.
Name the substance obtained from coal tar which is used to repel moths
Where was the first oil well drilled?
The first oil well was drilled at Pennsylvania, USA, in 1859.
Name two fractions of petroleum which are used as fuel.
Petrol and diesel.
Where and when was the first oil well drilled in India?
In 1867, at Digboi in Assam.
What is diesel?
Diesel is a fuel which is used in heavy vehicles, like buses and trucks. It is obtained after refining of petroleum.
Can we use all our natural resources forever?
No, we cannot use all our natural resources forever because these are going to exhaust one day.
The useful substances formed from natural gas and petroleum are called petrochemicals.
Why is coke not used as a fuel?
It is more valuable when used in the extraction of metals, hence not used as a fuel.
How do we obtain coke from coal?
By the process of destructive distillation.
Which fuel is promoted as a pollution-free fuel?
Why is natural gas a convenient fuel?
It is because natural gas can be supplied through pipes in homes and is less polluting.
Write some places of India where oil is found.
Assam, Gujarat, Bombay High and river basins of Godawari and Krishna.
Which constituents are separated from petroleum during refining?
Petroleum gas, petrol, diesel, lubricating oil, paraffin wax, etc.
Short Answer Type Questions
What is coal? Write its uses.
Coal is a black stone like substance. It is formed by the dead remains of the living organisms.
Uses of coal:
- Coal was used as a fuel in steam engines.
- Most of the thermal power plants still use coal as a fuel.
- Coal is still being used as kitchen fuel in some households, dhabas and restaurants.
- Many useful products like coke, coal tar and coal gas are made by processing coal.
What is coal-tar? How is it useful to us?
The black liquid obtained during destructive distillation of coal is known as coal tar. It is thick, viscous and has unpleasant smell. It is a mixture of hundreds of substances. It is used as a raw material for making various items like synthetic dyes, drugs, explosives, perfumes, plastics, paints, photographic materials, roofing materials, naphthalene balls, etc. It is used for making the surface of roads.
What happens after the petroleum is taken out of the oil well?
Crude oil needs to be processed to obtain useful products. After extraction from oil wells, petroleum is sent to oil refineries. Petroleum is subjected to fractional distillation in the oil refinery where various constituents of petroleum are separated through this process.
Define refining of petroleum.
Petroleum is a dark oily liquid. It has an unpleasant odour. It is a mixture of various constituents such as petrol, diesel, etc., and the process of separating these constituents from crude oil is called refining.
Why should we use certain resources, like coal and petroleum, judiciously?
As we know that coal and petroleum are fossil fuels. The dead organisms take millions of year to get converted into these fuels. On the other hand, the known reserves of these fuels will last only a few hundred years. Apart from this, these products are not environment-friendly as burning of these fuels is a major cause of air pollution and their use is also linked to global warming. Hence, we should use these resources only when absolutely required.
What can be the potential effect of petroleum products on the environment?
The effect of petroleum products on environment is as follows:
- While transporting petroleum and its products, there might be oil spillage.
- The process of refining petroleum generates various products that can lead to air and water pollution.
- Drilling of petroleum may result into serious disturbances in the aquatic life.
- Any leakage in the tanks in which petroleum is stored may lead to pollution and deterioration of groundwater.
Differentiate between renewable and non-renewable sources of energy with one example of each.
|Renewable Sources of Energy||Non-renewable Sources of Energy|
|1. Those sources of energy which are being produced continuously in nature and are inexhaustible are called renewable resources of energy.||1. Those sources of energy which have been accumulated in nature over a long period of time and cannot be quickly replaced if once exhausted, are called nonrenewable sources of energy.|
|2. Renewable resources of energy are available in unlimited quantities. Example: Air, water, solar radiation, etc.||2. Non-renewable sources of energy are available in limited quantity. Example: Coal, petroleum, natural gas, etc.|
Write down the consequence of excessive usage and mining of coal and petroleum.
Excessive usage and mining of coal and petroleum may:
- lead to energy crisis.
- result in creation of a large hollow space underneath which may cause minor earthquakes or landslides.
- lead to the greenhouse effect, acid rain and many health-related problems.
Why is coke considered a better fuel than coal? Give three reasons.
Coal and coke are both fuels. But, coke is considered to be a better fuel than coal because of the following reasons:
- Coke has higher calorific value than coal. So, coke produces more heat than the same mass of coal.
- Coke does not produce smoke on burning. So, there is lesser air pollution when coke is burnt as compared to the burning of coal.
What is the basis of the process of fractional distillation of petroleum?
The different components of petroleum have distinctly different boiling points. These components get separated in the fractional distillation tower when their boiling point is reached. The component having the maximum boiling point is at the bottom while the component having the minimum boiling point is at the top.
Long Answer Type Questions
Describe some ways to conserve fossil fuels.
Economic and controlled consumption of fossil fuels can help conserving our natural resources. Following ways and measures can conserve our fossil fuels:
- Vehicles should be driven at constant and moderate speed.
- Engines should be switched off at traffic lights or other temporary halts.
- Proper and regular maintenance of vehicles should be done.
- Vehicle pooling can reduce the number of vehicles plying on the road, thereby decreasing fuel consumption.
- At home, gas stoves should be cleaned properly and burners should not be left burning unnecessarily.
- Pressure cookers should be preferred to pans. If pans are being used, they should be properly covered and their bottoms should not have deposits of burnt oil.
- Small pans and burners should be used and pulses, etc., should be soaked in water before cooking them.
What are the different constituents of petroleum and their uses?
Following are the various constituents of petroleum oil obtained during fractional distillation in oil refineries:
- LPG or petroleum gas is used as a fuel for home and industry.
- Petrol is used as a motor fuel, aviation fuel and a solvent for dry cleaning.
- Kerosene is used as a fuel for stoves and lamps and also in jet aircrafts.
- Diesel is used as a fuel for heavy motor vehicles and electric generators.
- Lubricating oil is used for many lubricating purposes.
- Paraffin wax is used in ointments, candles and Vaseline.
- Bitumen is used in paints and also to surface the roads.
- Petrochemicals are used in the manufacture of detergents, polyester, nylon fibres, polythene and other man-made plastics.
Discuss the advantages of using compressed natural gas.
Advantages of CNG:
- CNG is a very important fossil fuel because it is easy to transport through pipes.
- CNG is also used for power generation and now used as a fuel for vehicles because it is less polluting.
- It is a cleaner fuel.
- Due to the absence of any lead or benzene content in CNG, the lead fouling of spark plugs is eliminated.
- CNG-powered vehicles have low maintenance cost when compared with other fossil fuel-powered vehicles.
- CNG fuel systems are sealed which prevents any spill or evaporation losses.
- CNG mixes easily and evenly in air being a gaseous fuel.
- CNG is less likely to auto-ignite on hot surfaces, since it has a high auto-ignition temperature and a narrow range of flammability. Thus it is less polluting and more efficient.
What is destructive distillation of coal? Describe the constituents obtained from this process.
The process in which a solid material (usually coal or wood) is heated at high temperature in absence of air to make coke, coal tar and charcoal is called. It is called ‘destructive’ because the chemical composition of the end product is significantly different from that of the input material.
a. Coke: Coke is almost pure form of carbon, is tough, porous and black. Coke is used in manufacture of steel and extraction of many metals.
b. Coal tar: It is a black thick liquid with an unpleasant smelt. Coal tar is a mixture of about 200 substances. It is used as a raw material for making various items, like synthetic dyes, drugs, explosives, perfumes, plastics, paints, photographic materials, roofing materials, naphthalene balls, etc. It is used for making the surface of roads. Bitumen (a petroleum product) has almost replaced coal tar for making road surface.
c. Coal gas: Coal gas is produced during the processing of coke from coal. Coal gas is used as a fuel in many industries which are situated near coal mines.
Prakash worked in an MNC which is 20 km away from the society. He had a CNG vehicle and he displayed a notice in his society informing the people that if anybody is interested to pool a car, feel free to contact him for the same.
a. What is the fuel used in CNG vehicle and how it is better than petrol?
b. Mention two harmful effects/ disadvantages of petrol as a fuel.
a. The compressed natural gas and methane is the fuel used in CNG vehicles. Compressed natural gas is a clean-burning fuel. It is actually the cleanest of all fossil fuels. Since natural gas is composed mainly of methane, burning it produces carbon dioxide and water vapour. These are the same compounds we exhale when we breathe. On the other hand, petroleum produces higher carbon emissions, nitrogen oxides and sulphur dioxide. Burning fuel oil also produces ash particulates that worsen pollution,
b. Two harmful effects of petrol are:
- It can lead to environmental pollution.
- It can be harmful to health.
Observe the given figure and answer the following questions:
a. Name the substance shown.
b. Name the process by which it is obtained.
c. Give any three uses of this substance.
a. Coal tar.
b. Destructive distillation.
c. It is used in the manufacturing of dyes, drugs, paints, naphthalene balls, etc.
Draw a line diagram to show the position of layers of natural gas, petroleum and water deposits.