Fuels

Q1. Define 1. Radioactivity:- The phenomenon of spontaneous and continuous emission of radiation from certain heavy element is called radioactivity. 2. Radioactive substance:- The substance, which spontaneously and continuously emits certain radiations is called a radioactive substance. 3. Fission products:- The products formed during a nuclear fission are called fission products. 4. Controlled chain reaction:- The process in which most of the neutrons liberated in the chain reaction are absorbed and only a few neutrons are allowed to carry on the reaction is called controlled chain reaction. 5. Un – controlled chain reaction:- The self accelerating chain reaction which takes place on its own around is called uncontrolled chain reaction. 6. Calorific value:- The quantity of heat produced by the complete combustion of unit mass of a fuel is called the calorific value of the fuel. 7. Disintegration of radioactive elements:- The process of continuous and spontaneous emission of radiation’s from a radioactive element to form a new element continues till a non – radioactive element is formed is called disintegration or decay of radioactive elements. 8. Nuclear wastes:- The harmful radioactive waste are produced by mining into enrichment and use in the nuclear reactors is known as nuclear wastes. Q2. Give scientific reasons:1. Boron steel or cadmium rods are used to control chain reaction Ans. 1. Boron steel or cadmium rods have a property of absorbing neutrons. 2. The rate of chain reaction can be reduced by absorbing some of neutrons which is generated, therefore boron steel or cadmium rods are used to control chain reaction. 2. The elements having atomic number greater than 82 are radioactive Ans. The nuclei of elements having atomic number greater than 82 are unstable. Hence, the elements having atomic number greater than 82 are radioactive. 3. Water gas is called blue gas. Ans. Water gas burns with bluish flame. Hence water gas is called blue gas. 4. Coal is fossil fuel. Ans. Coal is formed form the remains of plants and animals buried under the ground million of years back. Such remains are called fossils. Hence, coal is fossil fuel.

5. A nuclear reactor has thicker cover. (or) A thick coat of radiation absorbent materials is used around the atomic reactor. Ans. 1. Nuclear energy production in an atomic reactor is accompanied by release of radioactive pollutants and harmful radiation’s 2. These pollutants also produce harmful radiation, which are highly penetrating. 3. This radiation’s cause irreparable damage to the body cells. They cause hereditary changes. 4. This radiation’s should be prevented from leaking out. Hence, a nuclear reactor has a thicker cover. 6. Coke produces more heat than coal. (or) Coke is a superior fuel than wood and coal. Ans. 1. The calorific value of a fuel depends upon its carbon content. 2. Coke contains about 90 – 95% carbon. 3. The main combustible components of wood is cellulose, which is a carbonaceous substance. 4. Coal contains 10 – 80% carbon depending upon the type of coal. Hence, coke produces more heat than coal. 7. Hydrogen is not used as domestic fuel, even though it has high calorific value. Ans. 1. Hydrogen gas us explosive. 2. It forms explosive mixture with air. It is very difficult to handle hydrogen. Hence, hydrogen is not used as domestic fuel, even though it has high calorific value. 8. In the manufacture of ammonia producer gas is used. Ans. 1. Ammonia is the mixture of nitrogen and hydrogen in a suitable proportion. 2. In the producer gas, the percentage of nitrogen is 60%. Hence, the producer gas is used in manufacture of ammonia. 9. Petroleum is a fossil fuel. Ans. 1. Petroleum is formed from the remains of micro – organisms living under the sea. 2. When these organisms die, they sunk to the bottom of the sea and are gradually covered by sand and clay. 3. Due to the action of heat, pressure and certain catalytic actions taking place over millions of years, these remains are converted into a mixture of

hydrocarbons called petroleum. Such remains are called fossil fuels. Hence, petroleum is a fossil fuel. 10. Gaseous fuels are superior to the solid and liquid fuels. Ans. 1. They are extremely clean and convenient to use. 2. The burn almost instantaneously to provide heat energy. 3. The combustion of gaseous fuels can be easily controlled. 4. They have high calorific value. 5. They do not produce any solid waste products. 6. They can be transported easily and can be supplied through pipes at any distant place. Hence, Gaseous fuels are superior to the solid and liquid fuels. 11. Wood is a fuel. Ans. 1. A substance which on combustion produces heat, which can be used for various purposes, is called a fuel. 2. The main combustible component of wood is cellulose, which is a carbonaceous substance. 3. It burns in air forming carbon dioxide, water vapour and generate heat, hence, wood is a fuel. 12. Combustion of methane produces a large amount of heat. Ans. 1. Methane is a hydrocarbon. 2. The carbon atom in methane is bonded to four hydrogen atoms. 3. On combustion with oxygen in air, it forms carbon dioxide and water vapour and generate heat. Hence, wood is a fuel. 13. L.P.G is an ideal fuel. Ans. 1. L.P.G is liquefied petroleum gas. It contains butane and isobutene. The mixture is liquefied and filled in cylinders. 2. Hence, it is easy to handle and transport. 3. When the valve of the cylinder is opened the gaseous state and can be burned in the stove. Thus the supply of the gas can be controlled. Hence, L.P>G is an ideal fuel. 14. Conservation of fuels is essential. Ans. 1. The energy obtained from fuels is used for cooking food, driving engines and vehicles, getting light, and for industries. In the world industrialization is advancing fast. The urbanization is also very fast. For big cities and for the industries large amounts of fuels are required. 2. Currently 80% of the energy consumed in the world is obtained by burning carbon fuels or fossil fuels.

3. The reserves of these fuels are limited and getting exhausted very fast. Hence, conservation of fuels is essential. 15. The calorific value of water gas is greater than that of producer gas. Ans. 1. Water gas contains carbon monoxide (45%), hydrogen (45%) and other gases (10%). Producer gas contains carbon monoxide (30%), nitrogen (60%), and other gases (10%). 2. In water gas both the components are combustible. 3. In producer gas carbon monoxide is combustible, but nitrogen is non – combustible. The percentage of carbon monoxide in producer gas is lower than that in water gas. Hence, the calorific value of water gas is greater than that of producer gas. 16. In future, factories may be run with nuclear energy. Ans. 1. All factories require fuels for various operations. 2. Presently about 80% of the energy consumed is obtained by burning fossil fuels. 3. The reserves of fossil fuels are limited. They are getting depleted very fast. 4. Atomic nuclei are vast store of energy. Nuclear fission produces a large amount of energy from a very small mass of U – 235. This energy can be converted into other suitable forms of energy like electricity. Thus, this source of energy can sustain for a much longer time. Hence, in future, factories may be run with nuclear energy. Q3. Answer the following:1. What is a fuel? Ans. The substance which on combustion produce energy in the form of heat, which can be used for various processes is called a fuel. 2. How are fuels classified? Explain with examples. Ans. Fuels are classified as solid, liquid and gaseous fuels. Solid fuels --------- Wood, coal, coke etc. Liquid fuels --------- Petrol, Kerosene, fuel oil etc. Gaseous fuels -------- Natural gas, petroleum gas, water gas etc. 3 Give characteristic of an ideal fuel. Ans. 1. Ideal fuels should have high calorific value. 2. It should have low content of non – combustible material. 3. It should have moderate rate of combustion. 4. It should have definite ignition temperature. 5. Absence of poisonous products on combustion. 6. It should be available in large quantities at a cheaper rate.

7. It should be easy to store, transport and handle. 4. Write short note on calorific value? Ans. 1. The quantity of heal produced by a unit mass of fuel after combustion is called calorific value of the fuel. 2. It is expressed in calories/ gm in C.G.S and Joule / Kg in S.I. units. 3. The calorific value of gaseous fuel is the quantity of heat produced by complete combustion of unit volume of the fuel. 4. Charcoal – 33 Kj/g, Kerosene – 48 Kj/ g, L.P.G – 55 Kj/ G and biogas 35 – 40 Kj/ g. 5. Outline the used of atomic energy. Ans. The uses of atomic energy are as follows. 1. Atomic energy is used to generate electricity. 2. It is used to power submarines. 3. It is used to make atom bombs. 6. What are the effects of an explosion of an atom bomb? Ans. 1. The principle of uncontrolled chain reaction of U – 235 is used in atom bomb. 2. When it is exploded huge amount of energy and radiation s are emitted in short time. 3. AT place of explosions temperature shoots upto a few million – degree Celsius. 4. The energy produced under pressure is equal to several times atmospheric pressure. 5. The high temperature, high pressure and harmful intense radiation destroy all animals and plants in the surrounding area. 7. Write a brief account of emission, which is harmful to living organisms? Ans. Nuclear fission by – products are formed in nuclear explosions and in nuclear reactors. These by – products emit beta as well as more penetrating gamma radiations. When a human body is exposed to these radiations in a large dense, the body cells suffer irreparable damages. These radiations can induce some hereditary changes and thereby affect future generations too. 8. How is petroleum formed? Ans. 1. Petroleum is formed from the microorganisms living under the sea. 2. When these organisms die, they sink to the bottom and are gradually covered by sand and clay. 3. These remains are converted into hydrocarbons due to the action of heat, pressure and certain catalytic actions taking place over millions of years.

4. The resulting mixture of hydrocarbons rises through the porous rocks till it meets impermeable rocks. There it forms an oil trap. 9. How is petroleum obtained? Ans. 1. Petroleum reservoirs are located through a geological survey. 2. A hole is then drilled through the impervious rock, to the petroleum trap. 3. A pipe is introduced to the petroleum trap through this hole. Petroleum rises to the surface through this pipe. 10. What is L.P.G? From what source is L.P.G. obtained? Ans. L.P.G is liquefied petroleum gas. L.P.G is obtained by cooling natural gas and fractional distilling the liquid. It can also be obtained by the fractional distillation of petroleum. 11. What are the safety precautions to be taken while handling gaseous fuels? Why? Ans. 1. All gaseous fuels are readily combustible. 2. They may contain carbon monoxide, which is poisonous. 3. If a gaseous fuel contains hydrogen, we have to be very careful, as hydrogen forms an explosive mixture with air. 4. An explosion may occur if such a gas leaks and there is an accidental sparking or lighting of a match. Hence, it is essential that there should not be any leakage of a gaseous fuel. When the gas is not required, it should be completely turned off. 12. What precautions one should take while handling L.P.G safely? Ans. While handling L.P.G following precautions should be taken 1. The gas should be turn off by closing the valve when the gas is not required. 2. If L.P.G leaks out of the cylinder no matchstick should be struck in the house or any spark is allowed to strike. 3. The cylinder should be kept away from heat in a secured place. 13. Why is energy liberated in a nuclear fission process? (Or) Write Einstein’s equations for the energy liberated in a nuclear fission and explain it (Or) Give the relation between mass lost and the energy liberated during a nuclear fission reaction. Explain the terms involved. Ans. In a nuclear fission process, the mass of the original nucleus is always greater than the total mass of the fission products. The difference in the mass is converted into energy, according to Einstein’s equations. E = mc2 Where E = energy released, m = Loss in mass, c = speed of light in vacuum.

Q4. Write short notes on 1. Coal Ans. 1. Coal is fossil fuels. It has been formed over millions of years by the burial of plants. 2. Coal contains free amorphous carbon and complex carbon compounds formed from the parent plant matter. 3. Coal is classified into four types on the basis of its free carbon content. i. Peat (11%) ii. lignite (22%) iii. Bituminous(60%) iv. Anthracite (80%) 4. Destructive distillation of coal gives coke, coal, tar and coal gas. 2. Coke Ans. 1. Coke is obtained when coal is heated in the absence of air. 2. Coke contains about 90 -95% carbon. It does not contain any volatile matter. 3. It is hard and burns without producing smoke. It produces more heat than coal. 3. Petroleum Ans. 1. The dark oily liquid formed from the microorganism living under the sea and which occurs in the pores of sedimentary rocks is called petroleum. 2. It is a complex mixture of hydrocarbons. 3. It is formed from the remains of microorganisms due to the action of high pressure, heat and certain catalytic action over a period of millions of years. 4. On fractional distillation, petroleum gives useful products like, fuel oil, diesel, kerosene, petrol and petroleum gas. 4. Natural gas Ans. 1. The gas, which is found in the form of underground reservoirs in the region of coal and petroleum oil is called natural gas. 2. It contains hydrocarbons: methane (80 – 90%), ethane (6 – 10%), Propane (3 – 5%) and butane ( 1 – 2%) 3. Butanes (L.P.G) and other gases can be separated by cooling the natural gas and fractionally distilling the liquid. 5. L.P.G. Ans. 1. L.P.G is liquefied petroleum gas.

2. It mainly contains liquefied butane and isobutene. 3. It is obtained by cooling natural gas and fractionally distilling the liquid or by the fractional distillation of petroleum. 4. It is supplied in steel cylinders for cooking or industrial use. 6. Fossil fuels Ans. 1. Fossil fuels are formed over millions for years by the burial of plants and animals. 2. They contain energy rich molecules of carbon compounds originally made by plants. 3. Coal, petroleum and natural gas are examples of fossil fuels. About 80% of the energy consumed in the world is obtained by burning these fuels. 7. Fractional distillation of petroleum. Ans. 1. Petroleum or crude oil is brown black liquid. Petroleum is a mixture of several hydrocarbons. 2. When it is distilled, it separates into various fractions of hydrocarbons. 3. The compounds obtained from fractional distillation of petroleum which are useful as fuels are fuel oil, diesel, kerosene, petrol and petroleum gas. 8. Liquid fuels. Ans. 1. Liquid fuels are hydrocarbons. 2. Various hydrocarbons are present in petroleum. 3. When petroleum is fractionally distilled, it separates into various fractions of hydrocarbons. 4. The fractional distillation of petroleum yields three liquid fuels: gasoline or petrol, kerosene and fuel oil. Gasoline or petrol is used as motor fuel, kerosene as a domestic fuel and fuel oil is used for oil furnaces. 9. Water gas Ans. 1. Water gas is prepared by passing steam over while hot coke at about 14000 C. 2. It contains carbon monoxide (45%), hydrogen (45%) and other gases (10%) 3. It is used as a fuel and also a source of hydrogen. 10. Producer gas. Ans. 1. Producer gas is prepared by blowing insufficient quantity of air through a layer of red hot coal. 2. It contains carbon monoxide (30%), nitrogen (60%) and other gases (10%).

3. It is used for glass and metallurgical furnaces. It is also used as a source of nitrogen for preparation of ammonia. 11. Nuclear fission. Ans. 1. The process of splitting of heavy nucleus into two or more nuclei of smaller mass is called nuclear fission. 2. When U - 235 is bombarded with slow neutrons, each nucleus of U – 235 is split into one nucleus each of Ba and Kr, and three neutrons are set free. The products formed in a nuclear fission are called fission products.

3. As the mass of the original nucleus is always greater than the total mass of the fission products, the difference in the mass is converted into energy. A large amount of energy is liberated in the process of nuclear fission. 4. In a nuclear fission is allowed to continue uninterrupted, extremely large amount of energy is liberated in a short time. It is called uncontrolled chain reaction, which is the basis of an atom bomb. If most of the neutrons in the reactions are absorbed, using boron steel or cadmium rods, and only a few neutrons are allowed to carry on the chain reaction, the reaction is called a controlled chain reaction. It is the principle of working of a nuclear reactor. 12. Nuclear energy Ans. 1. The energy released during a nuclear fission process is called nuclear energy. For example when uranium – 235 is bombarded with slow neutrons, a chain reaction starts and nuclear energy is liberated. 2. In a nuclear fission process, the mass of the original nucleus is always greater than the total mass of the fission products. The difference in the mass is converted into energy, according to Einstein’s equations. E = mc2 Where E = energy released, m = Loss in mass, c = speed of light in vacuum. 3. Using an atom bomb, the nuclear energy is used for destruction. In a nuclear reactor, the nuclear energy is used to generate electricity. 13. Chain reaction Ans. 1. The self – multiplying process in which the neutrons ejected during the nuclear fission strike the neighbouring nuclei and bring about their fission is called chain reaction. 2. When U – 235 is bombarded with the neutrons, each nucleus of U – 235 splits into one nucleus each of Ba – 141 and Kr – 92, and three neutrons are set free. These neutrons bring about nuclear fission of three more U – 235 nuclei.

3. If a chain reaction is not controlled, a large amount of energy is liberated in an extremely short time. This principle is used in an atom bomb. 4. Using boron steel or cadmium rods, most of the neutrons liberated in the chain reactions are absorbed and only a few neutrons are allowed to carry on the reaction. It is called a controlled chair reaction. The working of a nuclear reactor is based on a controlled chain reaction. 14. Development of atomic energy in India. Ans. 1. The first nuclear reactors were erected at Bhaba Atomic Research Centre (BARC) in Mumbai, Currently Cirrus, Zerlina, Purnima and Dhurva reactors are in operations. There are mainly used for research and in the production of radioisotopes. 2. The first atomic power station was set up at Tarapore (Maharashtra) in 1969. It supplies electricity to the state of Maharashtra and Gujarat. 3. A few more atomic power stations have been set up in different part of the country. 15. Controlled chain reaction Ans. 1. The process in which most of the neutrons liberated in a chain reaction are absorbed and only a few neutrons are allowed to carry on the chain reaction is called a controlled chain reaction. 2. To control the chain reaction, boron steel or cadmium rods are used as they absorb neutrons. 3. The working of a nuclear reactor is based on a controlled chain reaction. 10+6. Nuclear reactor. Ans. 1. Uranium – 235 is used as a fuel in a nuclear reactor. 2. The nuclear fission of U – 235 is carried out by bombarding it with slow neutrons. 3. Boron steel or cadmium rods control the nuclear chain reaction set in. Thus, the liberation of energy in the fission process is controlled. 4. The energy released is used to vaporize water and the steam formed is used to run turbines. Thus, electricity is generated. Useful radioactive isotopes are also produced in a nuclear reactor.

Q5. Distinguis h between 1. Controlled chain reaction and uncontrolled chain reaction. Controlled Chain Reaction 1. The chain reaction in which most of the neutrons are absorbed in called a controlled chain reaction. 2. In this reaction most of the neutrons are absorbed using boron steel or cadmium rods. 3. This reaction is used for peaceful purposes, like generating electricity.

Uncontrolled Chain Reaction 1. The self – accelerating chain reaction, which takes place on its own, is called an uncontrolled chain reaction. 2. In this reaction neutrons are not absorbed. 3. This reaction leads to an explosion and hence is used for destructive purposes.

2. Producer gas and Water gas Producer Gas 1. Producer gas is prepared by passing insufficient quantity of air through red hot coal. 2. It contains mainly CO and N2. 3. It is used as a fuel and as illuminating gas.

Water Gas 1. Water gas is prepared over white hot coke at about 14000 C. 2. It contains CO and H2. 3. It is used as a fuel in glass furnace and metallurgical furnaces.

3. Solid Fuels and Gaseous Fuels. Solid fuels 1. The calorific value of solid fuels is lower than that of gaseous fuels. 2. These fuels are difficult to transport. 3. Solid fuels contain some amount of non – combustible material. 4. They do not burn quickly. 5. They produce solid waster products.

4. Coal and Coke

Gaseous fuels 1. The calorific value of gaseous fuels is higher than solid fuels. 2. These fuels can be transported easily. 3. Gaseous fuels do not contain non – combustible material. 4. They burn instaneously and their combustion can be controlled easily. 5. They do not produce any solid products.

Coal 1. Coal is a fossil fuel formed by the burial of plants. 2. It contains free amorphous carbon and complex carbon compounds. 3. It contains some volatile matter. 4. It burns with smoke. 5. It produces less heat than coke.

Coke 1. Coke is obtained by the destructive distillation of coal. 2. It contains about 90 – 95% carbon. 3. It does not contain any volatile matter. 4. It burns without producing smoke. 5. It produces more heat than coal.

5. Nuclear fusion and Nuclear fission Nuclear fusion 1. The nuclear reaction in which more than one nucleus of lighter elements combines to form a nucleus of a heavier element is called nuclear fusion. 2. This reaction takes place at a very high temperature of the order of million of degrees Celsius. 3. It is brought about a high temperature. 4. The mass of the product nucleus is more than the total mass of the reactant nuclei.

Nuclear fission 1. The reaction in which a heavy nucleus is split into two or more nuclei of smaller mass is called nuclear fission. 2. This reaction takes place at ordinary temperature. 3. It is brought about by bombarding a heavy nucleus by slow neutrons. 4. The total mass of the product nuclei is less than the mass of the reactant nucleus.