Welcome dear students! Today we are going to learn about Coal and Petroleum from Class 8 Science. We use various materials for our basic needs. Some of them are found in nature and some have been made by human efforts. Let us begin with Activity Three Point One. Make a list of various materials used by us in daily life and classify them as natural and man-made. Does this list include air, water, soil and minerals? Since all these are obtained from nature, they are called natural resources. Can we use all our natural resources forever? Can air, water and soil be exhausted by human activities? You have already studied about water in Class Seven. Is water a limitless resource? In the light of the availability of various resources in nature, natural resources can be broadly classified into two kinds. The first kind is 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. The second kind is Exhaustible Natural Resources. The amount of these resources in nature is limited. They can be exhausted by human activities. Examples of these resources are forests, wildlife, minerals, coal, petroleum, and natural gas. [CHECKPOINT]
Let us work through Activity Three Point Two. This is a group activity. Take some containers. Fill them with popcorn, peanuts, roasted gram, or toffees. Divide students into groups of seven each. Further divide each group into three subgroups containing one, two, and four students. Label them as first, second and third generation respectively. These sub-groups represent the consumers. As population is growing, second and third generations have larger number of consumers. Put one full container for each group on a table. Ask consumers of the first generation from each group to consume eatables from the container of their group. Now, ask the second generation consumers from each group to do the same. Ask students to observe carefully the availability of eatables in each container. If something is left in the containers, ask third generation from each group to consume it. Now, finally observe whether all the consumers of the third generation got the eatables or not. Also observe if anything is still left in any of the containers. Assume that the eatables in the container represent the total availability of an exhaustible natural resource like coal, petroleum or natural gas. Each group may have a different consumption pattern. Are the earlier generations of any group too greedy? It may be that the earlier generations in some groups were concerned about the coming generation and left something for them. [CHECKPOINT]
In this chapter we will learn about some exhaustible natural resources like coal, petroleum and natural gas. These were formed from the dead remains of living organisms, also known as fossils. So, these are all known as fossil fuels. Let us begin with section three point one, Coal. You may have seen coal or heard about it. It is as hard as stone and is black in colour. Coal 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. Where do we get coal from and how is it formed? About three hundred 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. [CHECKPOINT]
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. Let us examine these products. Coke is a tough, porous and black substance. It is an almost pure form of carbon. Coke is used in the manufacture of steel and in the extraction of many metals. Coal Tar is a black, thick liquid with an unpleasant smell. It is a mixture of about two hundred substances. Products obtained from coal tar are used as starting materials for manufacturing various substances used in everyday life and in industry, like synthetic dyes, drugs, explosives, perfumes, plastics, paints, photographic materials, roofing materials, and naphthalene balls used to repel moths and other insects. These days, bitumen, a petroleum product, is used in place of coal tar for metalling the roads. Coal Gas is obtained during the processing of coal to get coke. It is used as a fuel in many industries situated near the coal processing plants. Historically, coal gas was used for street lighting for the first time in London in eighteen ten and in New York around eighteen twenty. Nowadays, it is used as a source of heat rather than light. [CHECKPOINT]
Now let us move on to section three point two, Petroleum. You know that 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, meaning rock, and oleum, meaning oil, as it is mined from between the rocks under Earth. Do you know how petroleum is formed? 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. In the underground deposits, the layer containing petroleum oil and gas is above the water layer because oil and gas are lighter than water and do not mix with it. The world first oil well was drilled in Pennsylvania, United States of America, in eighteen fifty nine. Eight years later, in eighteen sixty seven, oil was struck at Makum in Assam. In India, oil is found in Assam, Gujarat, Mumbai High and in the river basins of Godavari and Krishna. [CHECKPOINT]
Let us discuss the refining of petroleum. Petroleum is a dark oily liquid with an unpleasant odour. It is a mixture of various constituents such as petroleum gas, petrol, diesel, lubricating oil, paraffin wax, and others. The process of separating the various constituents or fractions of petroleum is known as refining. It is carried out in a petroleum refinery. Let us go through the various constituents of petroleum and their uses. First, Petroleum Gas in liquid form, or L P G, is used as fuel for home and industry. Second, Petrol is used as motor fuel, aviation fuel, and solvent for dry cleaning. Third, Kerosene is used as fuel for stoves, lamps and for jet aircrafts. Fourth, Diesel is used as fuel for heavy motor vehicles and electric generators. Fifth, Lubricating oil is used for lubrication. Sixth, Paraffin wax is used in ointments, candles, and vaseline. Seventh, Bitumen is used in paints and road surfacing. [CHECKPOINT]
Many useful substances are obtained from petroleum and natural gas. These are termed as petrochemicals. These are used in the manufacture of detergents, fibres such as polyester, nylon, and acrylic, polythene and other man-made plastics. Hydrogen gas obtained from natural gas is used in the production of fertilisers like urea. Due to its great commercial importance, petroleum is also called black gold. Next, we will learn about section three point three, 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, or C N G. C N G 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 C N G 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 in Gujarat, some parts of Delhi and other places. Natural gas is also used as a starting material for the manufacture of a number of chemicals and fertilisers. India has vast reserves of natural gas. In our country, natural gas has been found in Tripura, Rajasthan, Maharashtra and in the Krishna Godavari delta. [CHECKPOINT]
Can coal, petroleum and natural gas be prepared in the laboratory from dead organisms? No. Their formation is a very slow process and conditions for their formation cannot be created in the laboratory. Let us proceed to section three point four, Some Natural Resources are Limited. You have studied that some natural resources are exhaustible like fossil fuels, forests, minerals and others. Coal and petroleum are fossil fuels. It required the dead organisms millions of years to get converted into these fuels. On the other hand, the known reserves of these will last only 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 better environment, smaller risk of global warming and their availability for a longer period of time. In India, the Petroleum Conservation Research Association advises people how to save petrol or diesel while driving. Their tips are to drive at a constant and moderate speed as far as possible, switch off the engine at traffic lights or where you have to wait, ensure correct tyre pressure, and ensure regular maintenance of the vehicle. [CHECKPOINT]
Now let us review what we have learnt. Coal, petroleum and natural gas are fossil fuels. Fossil fuels were formed from the dead remains of living organisms millions of years ago. Fossil fuels are exhaustible resources. Coke, coal tar and coal gas are the products of coal. Petroleum gas, petrol, diesel, kerosene, paraffin wax, lubricating oil are obtained by refining petroleum. Coal and petroleum resources are limited. We should use them judiciously. Now, let us solve the exercises together. Question one asks, what are the advantages of using C N G and L P G as fuels? According to the textbook, CNG is less polluting and a cleaner fuel, while LPG is used as fuel for home and industry. Question two asks, name the petroleum product used for surfacing of roads. The answer is bitumen. Question three asks, describe how coal is formed from dead vegetation. What is this process called? About three hundred million years ago, dense forests in low lying wetland areas got buried under soil due to flooding. Over time, more soil deposited, causing compression and rising temperature. Under high pressure and high temperature, dead plants slowly converted into coal. This slow process of conversion of dead vegetation into coal is called carbonisation. [CHECKPOINT]
Question four asks us to fill in the blanks. Part a: Fossil fuels are coal, petroleum and natural gas. Part b: Process of separation of different constituents from petroleum is called refining. Part c: The answer is CNG. The textbook states it is used for transport vehicles because it is less polluting and a cleaner fuel. Question five asks us to tick true or false. Part a: Fossil fuels can be made in the laboratory. False. Part b: C N G is more polluting fuel than petrol. False. Part c: Coke is almost pure form of carbon. True. Part d: Coal tar is a mixture of various substances. True. Part e: Kerosene is not a fossil fuel. False. Question six asks, explain why fossil fuels are exhaustible natural resources. Fossil fuels are exhaustible because they were formed over millions of years from dead organisms under specific conditions. Their natural reserves are limited, and human consumption depletes them faster than they can be replenished. Question seven asks, describe characteristics and uses of coke. Coke is a tough, porous and black substance. It is an almost pure form of carbon. It is used in the manufacture of steel and in the extraction of many metals. [CHECKPOINT]
Question eight asks, explain the process of formation of petroleum. Petroleum was formed from organisms living in the sea. When these organisms died, their bodies settled at the sea bottom and got covered with layers of sand and clay. Over millions of years, in the absence of air, under high temperature and high pressure, the dead organisms transformed into petroleum and natural gas. Question nine provides a table showing the total power shortage in India from nineteen ninety one to nineteen ninety seven and asks us to show the data in the form of a graph. To plot this, draw a horizontal X axis for the years and a vertical Y axis for the shortage percentage. Mark the years nineteen ninety one through nineteen ninety seven on the X axis. Mark percentages from zero to twelve on the Y axis. Plot the points: nineteen ninety one at seven point nine percent, nineteen ninety two at seven point eight percent, nineteen ninety three at eight point three percent, nineteen ninety four at seven point four percent, nineteen ninety five at seven point one percent, nineteen ninety six at nine point two percent, and nineteen ninety seven at eleven point five percent. Connect these points to form a line graph showing the trend of power shortage over the years. [CHECKPOINT]
Finally, let us look at the extended learning activities. First, get an outline map of India. Mark the places where coal, petroleum and natural gas are found. Show the places where petroleum refineries are situated. Second, choose any five families of your neighbourhood. Enquire whether their energy consumption has increased or decreased in the last five years, and what measures they adopt to conserve energy. Third, find out the location of major thermal power plants in India and consider the reasons for their being located at those places. We have now covered the entire chapter comprehensively. Remember that fossil fuels are precious gifts of nature that took millions of years to form. We must use them wisely and explore alternative energy sources for a sustainable future. Thank you for listening! Keep revising and practicing. Goodbye! [CHAPTER_COMPLETE]