NCERT Textbook Questions
The advantages of using CNG (Compressed Natural Gas) and LPG (Liquefied Petroleum Gas) as fuels are:
- They can be burnt directly.
- They can be transported easily through pipes.
- They are clean fuels and do not release smoke when burnt.
- They give a lot of heat energy.
Bitumen, a petroleum product, is used for surfacing roads these days. Earlier, coal tar was used for this purpose.
About 300 million years ago, the earth had dense forests in low-lying wetland areas. Due to natural processes like flooding, these forests got buried under the soil. As more soil deposited over them, they were compressed. The temperature also rose as they sank deeper and deeper. Under high pressure and high temperature, dead plants got slowly converted to coal. The slow process of conversion of dead vegetation into coal is called carbonisation.
(a) Fossil fuels are coal, petroleum and natural gas.
(b) Process of separation of different constituents from petroleum is called refining.
(c) Least polluting fuel for vehicle is CNG (Compressed Natural Gas).
(a) Fossil fuels can be made in the laboratory. (False)
(b) CNG is more polluting fuel than petrol. (False)
(c) Coke is almost pure form of carbon. (True)
(d) Coal tar is a mixture of various substances. (True)
(e) Kerosene is not a fossil fuel. (False)
Fossil fuels require millions of years to form from the dead remains of living organisms. The known reserves of these fuels are limited and will last only a few hundred years. Moreover, they cannot be created in a laboratory or by human effort in a short span of time. Therefore, they are exhaustible natural resources.
Characteristics:
- It is a tough, porous and black substance.
- It is an almost pure form of carbon.
Uses:
- It is used in the manufacture of steel.
- It is used in the extraction of many metals.
Petroleum was formed from organisms living in the sea. As these organisms died, their bodies settled at the bottom of the sea and got covered with layers of sand and clay. Over millions of years, absence of air, high temperature and high pressure transformed the dead organisms into petroleum and natural gas.
Extra Important Questions
Petroleum is a dark oily liquid. It is a mixture of various constituents such as petroleum gas, petrol, diesel, lubricating oil, paraffin wax, etc. The process of separating the various constituents/fractions of petroleum is known as refining. It is carried out in a petroleum refinery.
Natural gas is used:
- As a fuel for transport vehicles (CNG).
- For power generation.
- As a fuel in homes and factories (can be supplied through pipes).
- As a starting material for the manufacture of a number of chemicals and fertilisers.
We should use fossil fuels only when necessary because:
- Their burning causes air pollution.
- Their use is linked to global warming.
- They are available in limited quantities and taking millions of years to replenish.
Detailed Chapter Discussion: Coal and Petroleum
1. Natural Resources
We use various materials for our basic needs. Some of them are found in nature and some have been made by human efforts. Resources that are obtained from nature are called natural resources. Examples of natural resources include air, water, soil, and minerals.
Classification of Natural Resources
Natural resources can be broadly classified into two kinds:
Inexhaustible Natural Resources: These resources are present in unlimited quantity in nature and are not likely to be exhausted by human activities. Examples are sunlight and air.
Exhaustible Natural Resources: The amount of these resources in nature is limited. They can be exhausted by human activities. Examples are forests, wildlife, minerals, coal, petroleum, natural gas etc.
2. Fossil Fuels
Some exhaustible natural resources like coal, petroleum, and natural gas were formed from the dead remains of living organisms (fossils). These are all known as fossil fuels. They take millions of years to form and cannot be replenished quickly.
Fossil fuels are the major source of energy for us today. We burn them to generate electricity, run vehicles, and cook food. However, burning fossil fuels releases gases that cause pollution and contribute to global warming.
3. Coal
Coal is a hard fossil fuel that is black in colour. It is one of the fuels used to cook food. Earlier, it was used in railway engines to produce steam to run the engine. It is also used in thermal power plants to produce electricity. Coal is also used as a fuel in various industries.
Story of Coal
About 300 million years ago the earth had dense forests in low-lying wetland areas. Due to natural processes like flooding, these forests got buried under the soil. As more soil deposited over them, they were compressed. The temperature also rose as they sank deeper and deeper. Under high pressure and high temperature, dead plants got slowly converted to coal. As coal contains mainly carbon, the slow process of conversion of dead vegetation into coal is called carbonisation. Since it was formed from the remains of vegetation, coal is also called a fossil fuel.
4. Products from Coal
When heated in air, coal burns and produces mainly carbon dioxide gas. Coal is processed in industry to get some useful products such as coke, coal tar and coal gas.
| Product | Description | Uses |
|---|---|---|
| Coke | Tough, porous and black solid. Almost pure carbon. | Manufacture of steel, extraction of metals. |
| Coal Tar | Black, thick liquid with unpleasant smell. Mixture of many substances. | Manufacturing synthetic dyes, drugs, explosives, perfumes, plastics, paints, photographic materials, roofing materials, etc. |
| Coal Gas | Gaseous fuel obtained typically during processing of coal to get coke. | Used as a fuel in many industries situated near the coal processing plants. Earlier used for lighting. |
Did you know? Naphthalene balls used to repel moths and other insects are also obtained from coal tar.
5. Petroleum
Petrol is used as a fuel in light automobiles such as motor cycles/scooters and cars. Heavy motor vehicles like trucks and tractors run on diesel. Petrol and diesel are obtained from a natural resource called petroleum. The word petroleum is derived from petra (rock) and oleum (oil) as it is mined from between the rocks under earth.
Formation of Petroleum
Petroleum was formed from organisms living in the sea. As these organisms died, their bodies settled at the bottom of the sea and got covered with layers of sand and clay. Over millions of years, absence of air, high temperature and high pressure transformed the dead organisms into petroleum and natural gas. The layer containing petroleum oil and gas is above that of water because oil and gas are lighter than water and do not mix with it.
6. Refining of Petroleum
Petroleum is a dark oily liquid. It has an unpleasant odour. It is a mixture of various constituents such as petroleum gas, petrol, diesel, lubricating oil, paraffin wax, etc. The process of separating the various constituents/fractions of petroleum is known as refining. It is carried out in a petroleum refinery.
Constituents of Petroleum and Uses
- LPG (Liquid Petroleum Gas): Fuel for home and industry.
- Petrol: Motor fuel, aviation fuel, solvent for dry cleaning.
- Kerosene: Fuel for stoves, lamps and for jet aircrafts.
- Diesel: Fuel for heavy motor vehicles, electric generators.
- Lubricating Oil: Lubrication.
- Paraffin Wax: Ointments, candles, vaseline etc.
- Bitumen: Paints, road surfacing.
Note: Many useful substances are obtained from petroleum and natural gas. These are termed as 'Petrochemicals'. They are used in the manufacture of detergents, fibres (polyester, nylon, acrylic), polythene and other man-made plastics. Hydrogen gas obtained from natural gas, is used in the production of fertilisers (urea).
7. Natural Gas
Natural gas is a very important fossil fuel because it is easy to transport through pipes. Natural gas is stored under high pressure as Compressed Natural Gas (CNG). CNG is used for power generation. It is now being used as a fuel for transport vehicles because it is less polluting. It is a cleaner fuel.
The great advantage of CNG is that it can be used directly for burning in homes and factories where it can be supplied through pipes. Such a network of pipelines exists in Vadodara (Gujarat), some parts of Delhi and other places.
8. Conservation of Resources
It took millions of years for the conversion of dead organisms into these fuels. On the other hand, the known reserves of these will last at most a few hundred years. Moreover, burning of these fuels is a major cause of air pollution. Their use is also linked to global warming. It is therefore necessary that we use these fuels only when absolutely necessary. This will result in a better environment, smaller risk of global warming and their availability for a longer period of time.
PCRA Tips
In India, the Petroleum Conservation Research Association (PCRA) advises people how to save petrol/diesel while driving. Their tips are:
- Drive at a constant and moderate speed as far as possible,
- Switch off the engine at traffic lights or at a place where you have to wait,
- Ensure correct tyre pressure, and
- Ensure regular maintenance of the vehicle.
50 Key Facts: Coal and Petroleum
Resources that are obtained from nature are called natural resources. They include air, water, soil, minerals, forests, and wildlife. These are essential for the survival and development of human civilization.
Exhaustible natural resources are those that are present in limited quantities in nature. They can be exhausted by continuous human usage. Examples include coal, petroleum, natural gas, forests, and minerals.
Inexhaustible natural resources are present in unlimited quantities in nature and are not likely to be exhausted by human activities. Solar energy (sunlight) and wind energy are prime examples.
Fossil fuels are formed from the dead remains of living organisms (fossils) buried under the earth for millions of years. Coal, petroleum, and natural gas are the main fossil fuels.
Carbonisation is the slow chemical process of conversion of dead vegetation into coal under high pressure and high temperature over millions of years inside the earth.
Coal is primarily composed of carbon. It also contains hydrogen, oxygen, nitrogen, and sulphur in small amounts. The quality of coal depends on its carbon content.
Coke is a tough, porous, and black substance obtained by the destructive distillation of coal. It is an almost pure form of carbon and produces very little smoke when burnt.
Coke is used as a reducing agent in the extraction of metals like iron, copper, lead, etc. It is also used in the manufacture of steel and as a fuel.
Coal tar is a black, thick liquid with an unpleasant smell. It is a mixture of about 200 different organic substances. It is obtained as a by-product during the manufacture of coke from coal.
Coal tar is used as a starting material for manufacturing synthetic dyes, drugs, explosives, perfumes, plastics, paints, photographic materials, and roofing materials.
Naphthalene balls, used to repel moths and other insects from clothes, are obtained from coal tar. This demonstrates the wide range of useful chemicals derived from coal.
Coal gas is a gaseous fuel obtained during the processing of coal to get coke. It is a mixture of hydrogen, methane, and carbon monoxide. It creates a lot of heat when burnt.
Coal gas was used for street lighting for the first time in London in 1810 and in New York around 1820. Nowadays, it is used more as a source of heat than light.
The word petroleum is derived from the Latin words 'petra' meaning rock and 'oleum' meaning oil. It is called petroleum because it is mined from between the sedimentary rocks under the earth.
Petroleum was formed from organisms living in the sea. Dead organisms settled at the bottom and were covered with sand/clay. Over millions of years, high heat/pressure transformed them into oil and gas.
Petroleum Refining is the process of separating the various constituents or fractions of petroleum. It is carried out in a petroleum refinery using a process called fractional distillation.
The main constituents obtained from petroleum refining are Petroleum Gas (LPG), Petrol, Kerosene, Diesel, Lubricating Oil, Paraffin Wax, and Bitumen.
Liquefied Petroleum Gas (LPG) consists mainly of butane. It is easily liquefied under pressure and is used as a fuel for home (gas cylinders) and industry. It is a clean-burning fuel.
Petrol is a liquid fuel used in light motor vehicles like scooters, motorcycles, and cars. It is also used as a solvent for dry cleaning clothes.
Kerosene is used as a fuel for stoves, lamps, and for jet aircrafts. It is less volatile than petrol but more volatile than diesel.
Diesel is used as a fuel for heavy motor vehicles like trucks, buses, and tractors. It is also used to run electric generators. It provides more energy per litre than petrol.
Lubricating oil is a fraction of petroleum used for lubrication in engines and machines. It reduces friction between moving parts, increasing efficiency and lifespan.
Paraffin wax is obtained from petroleum. It is used in making ointments, candles, vaseline, grease proof paper, and cosmetics. It is a solid at room temperature.
Bitumen is a petroleum product used in paints and for road surfacing. It has largely replaced coal tar for metalling roads because it is more durable.
Petrochemicals are useful substances obtained from petroleum and natural gas. They are used in the manufacture of detergents, fibers (polyester, nylon, acrylic), and plastics (polythene).
Natural gas consists mainly of methane (CH4). It is found deep under the crust of the earth either alone or along with petroleum oil. It is a very important fossil fuel.
Compressed Natural Gas (CNG) is natural gas stored under high pressure. It is used as a fuel for transport vehicles because it is less polluting and cleaner than petrol or diesel.
CNG burns completely leaving no residue. It is eco-friendly. It can be supplied directly from the gas fields through pipes to homes and factories for burning.
Petroleum is also known as 'Black Gold'. This is because it is black in colour (as crude oil) and it is very valuable commercially due to the large number of useful products obtained from it.
The world's first oil well was drilled in Pennsylvania, USA, in 1859. Eight years later, in 1867, oil was struck at Makum in Assam, India.
In India, oil is found in Assam, Gujarat, Mumbai High, and in the river basins of Godavari and Krishna. Exploration is continuing to find new reserves.
Burning of fossil fuels like coal and petroleum releases carbon dioxide (CO2) into the atmosphere. Increased CO2 traps heat, leading to global warming, which causes climate change.
Burning of coal and diesel releases sulphur dioxide gas. It is an extremely suffocating and corrosive gas. Petrol engines give off oxides of nitrogen. These oxides dissolve in rain to form acid rain.
Oxides of sulphur and nitrogen released from burning fossil fuels dissolve in rainwater to form sulphuric acid and nitric acid. This is called acid rain. It is harmful for crops, buildings, and soil.
PCRA stands for Petroleum Conservation Research Association. It is an organization in India that advises people on how to save petrol and diesel while driving to conserve resources and reduce pollution.
To save fuel: drive at a constant and moderate speed; switch off the engine at traffic lights; ensure correct tyre pressure; and ensure regular maintenance of the vehicle.
Hydrogen gas is obtained from natural gas. It is used in the production of fertilisers (urea). This is an industrial application of natural gas other than as a fuel.
Petroleum oil and natural gas are lighter than water. That is why they collect above the water layer in underground resevoirs, which helps in their extraction.
Petroleum reservoirs are trapped between layers of impervious rocks (rocks that do not allow liquid to pass through). This prevents the oil and gas from escaping to the surface.
There are different varieties of coal depending on carbon content: Peat (lowest quality), Lignite (brown coal), Bituminous (common coal), and Anthracite (highest quality, hardest).
Excessive use of fossil fuels is leading to their rapid depletion. This could lead to an energy crisis in the future if alternative sources of energy are not developed and adopted.
Solar energy is a renewable and inexhaustible alternative to fossil fuels. It is clean and abundant. Technologies like solar panels are used to harness this energy for electricity and heating.
The 3R principle (Reduce, Reuse, Recycle) helps in conserving natural resources. Reducing usage, reusing products, and recycling materials saves energy and creates less demand for new resources.
Coal is formed from dead vegetation (trees, ferns, plants) that existed in swampy forests millions of years ago. This vegetation was buried and transformed under heat and pressure.
Petroleum is formed from dead organisms (plankton, algae) that lived in the sea. They settled at the bottom and were covered by sediments, eventually turning into oil and gas.
Fractional distillation works on the principle that different components of petroleum have different boiling points. The crude oil is heated, and vapours condense at different heights in a tower.
Coal is the primary fuel used in thermal power plants to generate electricity. Burning coal heats water to produce steam, which turns turbines to generate electricity.
Sustainable development means meeting the needs of the present generation without compromising the ability of future generations to meet their own needs. Preserving fossil fuels is a part of this.
The petrochemical industry is a vast sector that produces chemicals from petroleum and natural gas. These chemicals are the building blocks for plastics, rubbers, fertilizers, and textiles.
Biofuels (like biodiesel and ethanol) and battery technologies (for electric vehicles) are being developed to reduce our dependence on fossil fuels like petrol and diesel.