A branch of science that deals with the study of properties, composition and structure of materials, around us.

An element is a substance, which can neither be broken nor build from two or more simple substances.105 elements are known today.

A compound is a substance, which is made up of two or more elements, combined in fixed proportion by weight, and is decomposable into constituents through any method.

A mixture is obtained by mixing any two elements or compounds in any proportion. It may be homogenous or heterogeneous.

Structure of the atom

John Dalton put the theory that the all matter is made up of atoms. According to him; the atom is smallest particle of matter and may have independent existence. According to, modern atomic theory, an atom is made up of three particles protons, neutrons and electrons.

An atom is neutral, as the number of protons and electrons are the same.

The nucleus, is the central part of the atom, and is embedded with proton and neutrons. The electrons surround the nucleus, and lie in orbits & are in continuous motion.

The distribution of electrons in the orbits is called the electronic configuration.

The atomic weight equals the total number of protons & neutrons. The atomic number of atom equals the total number of electrons.

Periodic table of elements

D.I Mendeleev was the first person, which devised the periodic table of elements. According to him, elements can be arranged according to their atomic weight, and will show periodicity of the properties. All elements were arranged according to their atomic weights in horizontal and vertical columns.There are seven periods (horizontal columns) and 18 groups (vertical columns).The vertical columns were further subdivided into sub-groups, thus numbered 1A-7A, 1B-7B, 8 and O groups,

All properties of all elements in a one subgroup are same. According to Modern Periodic Table, all elements are arranged according to the atomic numbers, and groups & sub groups are alike with Mendeleev’s Periodic Table.

Some important elements and their uses

Helium	it is used as gas in air ships & balloons. Helium is mixed with O2 to inhale during sea diving; also used in welding of metals.
Lithium	Its various compound are used as drugs for mental depression (Li2CO3), also used gout & rheumatism (lithium salicylate, lithium benzoate & citrate); to produce thermonuclear energy.
Beryllium	Beryllium with other metals form alloys, having high strength.
Fluorine	It is used to manufacture uranium hexa-floride (UF6) to generate nuclear power; in Ferons, fluorine is used as refrigerants or aerosols. Cryolite is used in aluminium making.
Sodium	It forms an antiknock alloy with lead. It is also used as heat exchanger in nuclear reactions.
Magnesium	This element is used for flash powers. It forms duralium metal with aluminium and used for aeroplane making.
Potassium	It is used in photovoltaic cells & Na-K alloy are used in high temperature thermometers.
Titanium	It is used to resist corrosion. Ti steel is utilized in making of supersonic aircrafts, jet engines, turbine engines; it hardens and steel.
Vanadium	Ferro-vanadium alloy are specially used to make steels.
Chromium	used with steel to produce special steels like chrome-chrome & stainless steels.
Manganese	It is used to manufacture Mn steel; Mn in steel imparts hardness & toughness, which are used in making of rock crushers etc.
Cobalt	It makes alloys like steel, and used to make permanent magnets, to make cutting tools, surgical instruments; also used electroplating.
Nickel	It imparts hardness to steel, and these are used to make armour plates. Invar (Ni 35% pronicket cups) (Ni 20%)-bullet sheaths. Nichrome (Nl 60%, CR 15%, Fe 25%)-electrical filaments. Also used to form spatulas, crucibles & tongs.
Gallium	is used in quartz thermostats.
Arsenic	Arsenic compounds are useful for weed killing.
Selenium	is used in photovoltaic cells.
Strontium	Strontium is used to recover sugar from molasses.
Zirconium	is used to make bulletproof clothes.
Molybdenum	Molybdenum steel with nickel is used to make the gun barrels.
Palladium	is alloyed with gold which serves as substitute for platinum
Cadmium	Cadmium rods are used in the nuclear reactors; it makes fusible alloys such as wood’s metal, rose metal.
Tin	It is utilized in making of such alloys, solder Britannia metal, white metal, bell metal, rose metal & solder etc.
Tungsten	wires used to make filaments of the electrical appliances.
Platinum	It is inert to oxygen and water thus utilized to made crucibles etc.
Bismuth	It is employed to make fusible alloys, to make automatic electrical fuses, automatic fire alarms etc.

Hydrogen

Water is abundant in all chemical substances.It is very important for life, and all organic life have 50 to 70% of water.Water exists in all three kinds of matter solid, liquid and gas.Water is a universal solvent except a few substances. It has importance in agriculture, industry including chemical.A drinking water contains small amounts of different salts and gases.Rainwater is the purest form of the natural water.

Hydrogen has three types of isotopes

Proteium (1H)	contain only one proton
Deutrium or heavy hydrogen (2H or D)	one proton & one neutron
Tritium (3H or T)	one proton and two neutrons

The Proteium isotope is the most abundant of all the hydrogen isotopes (up to 99.985%).

Heavy water (D2O) - is used as moderator in the nuclear reactors to slow down the fast moving neutrons. Hydrogen occurs in the nature in large amounts in water, acids, carbohydrates, plants and animals proteins, vitamins, wood, coal tar, oil & natural gas etc.

Hydrogenation is process, during which the vegetable oil in the presence of catalyst (nickel) is converted into vegetable ghee.

Hydrogen peroxide

Hydrogen peroxide is utilized in bleaching of wool and hair. In medicine, it is used as disinfectant. It is utilized in restoration of old parting in which lead oxide has been used as a white paint.

White lead in these paintings changes into black lead Sulphide on exposure to atmosphere. Hydrogen peroxide is used to oxidize black lead Sulphide to white lead Sulphate.

Hydrogen peroxide is used as a propellant for torpedoes. Concentrated hydrogen peroxide is now finding an important use as an oxidant for rocket fuel.

Water

• Water is the principal constituent 75% of earth’s surface and is an essential component of plants and animals in life processes.
• It constitutes about 65% of the human body and up to 95% of many plants.
• Water molecule is a bent molecule with a bond angle of 104.5.
• Water is a substance of great complexity.
• Water is a good solvent of ionic compounds but a poor one for covalent compounds.
• A number of ionic compounds like silver chloride, calcium fluoride, barium Sulphate and aluminium trifloride, are non soluble in water.
• Some carbon compounds such as alcohols, carboxylic acids and carbohydrates does not dissolve in water.

Soft and Hard Water

Soft water is either pure water (e.g. rain water), or soft water in which the dissolved impurities (e.g. sodium salts) do not hinder its lather forming property. Soft water forms rich lather with soaps immediately.

Hard water does not later with soaps immediately. IT is due to presence of some salts in water (mainly calcium and magnesium salts). Hard water is objectionable for many uses, particularly for washing, bathing or making steam in the industries. If hard water used in the industries. It leads to the formation of deposits in the boilers. A number of methods are generally employed for softening of water (i.e. converting the hard water into soft water). The hardness of water is of two types: -

Temporary hardness : It can be removed by boiling the water. It is due to the presence of bicarbonates of calcium or magnesium. On boiling, these bicarbonates decompose, and insoluble carbonates are removed by the filtration.It can also be removed by addition of a calculated amount of lime (calcium hydroxide)

Permanent hardness: It is due to presence of soluble calcium or magnesium salts (others than bicarbonates). From this type water hardness can be removed by precipitation (use of washing soda), by exchange of Ca, Mg ions with sodium ions in the zeolities. With use of calgon, the renders Ca & Mg ions ineffective.

Carbon and its compouds

• Carbon is the most abundant element on the earth. Carbon is most useful to the mankind, as it has served men with various ways-food material, fuels, cloths and drugs, which are made up of carbon compounds.
• Its various allotropic forms are diamond, graphite, coal, coke, etc. and each form is characterized by individual physical and chemical properties.
• Diamond is the most purest form of carbon, and are formed due to crystallization of carbon. The structure of diamond is a 3-D polymeric, in the form of tetrahedron, which makes the diamond one of the hardest material.
• Graphite is softest form of carbon, consists of sheets of carbon and which are atom, held together by vertical covalent bonds.

CO2 is present in the atmosphere with a concentration of 325 ppm. A natural equilibrium is maintained in level of CO2 in the atmosphere by photosynthesis & precipitation in form of carbonates, deposited as carbonate rocks and are it is also produced by combustion of organic matters.

In recent times concentration of CO2 has increased considerably after Industrial Revolution, and is one of cause for the greenhouse effect.

The carbon monoxide (CO) has very small amount in the atmosphere, and is produced during the combustion of oil in an automobile engine, or during when fuel is burned in a closed room.

CO is a colourless, odourless gas, and is a poisonous gas.

Its poisonous nature is due to the fact that combines with the haemoglobin of the blood, and forms indecomposable carboxy-haemoglobin, thus affecting oxygen carrying ability of the haemoglobin; this disorder is known as asphyxiation.

The carbon cycle maintains the level of CO2 in the environment, between production & consumption at a constant (0.04%) rate.

Nitrogen and its compounds

It is very essential for life; as it controls over-reactive oxygen in the air and in the form of protein & nucleic acid form a basis of life.

Ammonia is an important compound of nitrogen and is obtained commercially by the Haber’s process. Ammonia is used as a refrigerant, manufacture of fertilizers, medicines and others.

Nitrogen is an essential constituent of the plant and animal life. Animal gets nitrogen supply from plant and plants get it from the soil.

The nitrogen cycle maintains the nitrogen level in the environment. The blue green algae are adaptable enough to convert the atmospheric nitrogen into nitrogenous compounds.

Metals and their extraction

Metals are found in nature in the form of minerals or oreas. The native minerals are the metals occurring in a free state e.g. cooper, silver, gold etc. A mineral is composed of naturally occurring metals.

An ore is a mineral, from which metal can be extracted economically. Extration of a metal from an ore involves following steps.

i)      Beneficiation (concentration of the ore) in this process, ore is usually crushed and grounded until all the particles are broken down. The unwanted material (gangue) is removed using the washing, foam flotation process, magnetic separation, based upon difference between the ore and gangue.

ii)     Conversion of concentrated ore into simpler compounds- carbonated ores is converted into metal oxides by calcination and sulphide ores are converted into metal oxides by roasting.

iii)    Reduction of metal oxide: The metal oxides are reduced to meal by carbon, aluminum or electrolyte, reduction.

iv)    Refining of the impure metal: Refining is done to purify the metal, and is performed by electrolysis, liquation, distillation and oxidation methods

Ores of some important elements
Lithium	Lithium mica, Petalite, Spodumene
Sodium	Common salt (rock salt), Chile saltpetre, Cryolite,
Beryllium	Beryl
Magnesium	Dolomite, Carnallite, Asbestos
Calcium	Limestone, Chalk, Calcite, Marble, Dolomite, Stalactite, Stalagmite
Radium	Pitch blende, Carnotite
Aluminium	Bauxite, Cryolite, Corundum
Tin	Cassiterite, Tinstone
Lead	Galena
Phosphorous	Phosphorite, Apatite , Chlorple
Sulphur	Native sulphur
Titanium	Rutile, Ilmente
Chromium	Chromite
Molybdenum	Molybdenite, Wulfranite
Tungsten	Wolframite, Sheelite
Manganese	Pyrolusite, Braunite,  Hausmantite
Iron	Haematite, Magnetite, Siderite
Cobalt	Cobalitite
Nickel	Pentlendite,Garnierite, Kupfer’s nickel
Copper	Copperpyrite,Cuperite,Malachite
Silver	Silver glance (Argentite), Horn silver, Ruby silver , (pyrargrite)
Zinc	Zinc blende, Calamine
Thorium	Monazite, Thorite

Alloy

Substance composed of two or more metals. Alloys, like pure metals, possess metallic luster and conduct heat and electricity well, although not generally as well as do the pure metals of which they are formed. Compounds that contain both a metal or metals and certain nonmetals, particularly those containing carbon, are also called alloys. The most important of these is steel. Simple carbon steels consist of about 0.5 percent manganese and up to 0.8 percent carbon, with the remaining material being iron.

An alloy may consist of an intermetallic compound, a solid solution, an intimate mixture of minute crystals of the constituent metallic elements, or any combination of solutions or mixtures of the foregoing. Intermetallic compounds, such as NaAu2, CuSn, and CuAl2, do not follow the ordinary rules of valency. They are generally hard and brittle; although they have not been important in the past where strength is required; many new developments have made such compounds increasingly important. Alloys consisting of solutions or mixtures of two metals generally have lower melting points than do the pure constituents. A mixture with a melting point lower than that of any other mixture of the same constituents is called a eutectic. The eutectoid, the solid-phase analog of the eutectic, frequently has better physical characteristics than do alloys of different proportions.

The properties of alloys are frequently far different from those of their constituent elements, and such properties as strength and corrosion resistance may be considerably greater for an alloy than for any of the separate metals. For this reason, alloys are more generally used than pure metals. Steel is stronger and harder than wrought iron, which is approximately pure iron, and is used, in far greater quantities. The alloy steels, mixtures of steel with such metals as chromium, manganese, molybdenum, nickel, tungsten, and vanadium, are stronger and harder than steel itself, and many of them are also more corrosion-resistant than iron or steel. An alloy can often be made to match a predetermined set of characteristics. An important case in which particular characteristics are necessary is the design of rockets, spacecraft, and supersonic aircraft. The materials used in these vehicles and their engines must be light in weight, very strong, and able to sustain very high temperatures. To withstand these high temperatures and reduce the overall weight, lightweight, high-strength alloys of aluminum, beryllium, and titanium have been developed. To resist the heat generated during reentry into the atmosphere of the earth, alloys containing heat-resistant metals such as tantalum, niobium, tungsten, cobalt, and nickel are being used in space vehicles.

Name of the Alloy	Composition	Uses
Alnico	Fe 63% + Ni 20% + Al 12% + Co 5%	?For making permanent magnets
Aluminium	Al 90% + Cu 10%	?For making picture frames, coins, trays, etc.
Alclad	Alloy of Aluminum	?For making sea planes.
Brass	Cu 70% + Zn 30%	?For making utensils.
Bell metal (Kansa)	Cu 80% + 20% Sn (Tin)	?For making bells.
Babbit metal	Cu 3-7% + Sn 88-90% + Sb 7-4%	?For making bearings.
Britania metal (Pewter)	Cu 1-3% + Sn 85-95% + Sb 6-10%	?For making cup, mugs, etc.
Constantan	Cu 60% + Nickel 40%	?For making resistance boxes thermocouples
Delta metal	Cu 55% + zinc 41% + Fe 4%	?For making shops, bearings and propellers
Duralumin	Cu 4% + Al 95.5% + Mn (0.5%)	?For making aeroplane parts.
Dutch metal	Cu + Zn	?For making artificial jewellery.
Electron	Mg 95% + Zn 5%	?For manufacture of aircraft and automobile parts.
Ferromanganese (spiegeleisen)	Mn 78-82% + C 75% + P 0.35% + S 0.5% + Si 1.25%	?In steel manufacture.
Ferro nickel	Fe 95-97.5% + Ni 2.5-5%	?Used in the manufacture of cables, propeller, shafts, armour plates, etc.
Ferro vanadium	Fe + V 30-40%, C 3.5% + P 0.25% + S 0.4% + Si 13% + Al 1.5%	?For making springs, axles and shafts, etc.
German silver or Nickel silver	Cu 55-65% + Zn 13-27% + Ni 10-30%	?For making cutlery, table ware, resistance coils, ornaments, etc.
Gun metal	Cu 88% + Sn 10% + Zn 2%	?In making guns, bearings and gears, etc.
Invar	Fe 64% + Ni 36%	?For making measuring instruments and clock pendulums.
Magnalium	Al 98% + Mg 2%	?For making cheap balances.
Monel metal	Cu 30% + Ni 67% + Mn or Fe 3%	?Chemical plants, automobile engine parts, household sinks, etc.
Manganese Steel	Fe 85% + Mn 13% + Carbon	?For making rail lines safes, rock drills, etc.
Nichrome	Ni 60% + Cr 15% + Fe 25%	?For making electrical resistances.
Nickel steel	Fe 96-98% + Ni 2-4%	?For making shafts and wire cables.
Nickel coinage alloy	Ni 25% + Cu 75%	?For making coins.
Phosphorus bronze	Cu 85% + Sn 13% + P 2%	?Gears, aerials, propellers.
Permalloy	Fe 21% + Ni 78% + Carbon	?For making electromagnets and ocean tables.
Rose metal	Bi 50% + Pb 25% + Sn 5%	?For making safety plug in boilers, pressure cookers.
Solder	Sn 67% + Pb 33%	?Artificial Jewellery.
Stainless steel	Fe 73% Cr 18% + Ni 8% + Carbon	?For making cutlery, automobile parts, surgical instruments, etc.
Stellite	Cr + W + Ni	?For manufacture of high speed tools, cutlery surgical instruments.
Type metal	Pb 82% Sb 15% + Sn 3%	?For making type of printing.
Tungsten steel	Fe 83% + W 14% + Cr 3%	?For making cutting tools for high speed lathes.
Wood metal	Pb 25% + Sn 12.5% + Cd 12.5% + Bi 50%	?In automatic sprinklers.

Electrolysis

Electrolysis is a process whereby a compound commonly a salt is split into ions by the passge of electric current in a solution or molten state. The negative ions move towards the anode while the positive ions move towards the cathode.

It is of greater significance, since it had led to the development of important technical processes associated with the production and purification of non-ferrous metals and electro synthesis of organic compounds.

Electrolysis has found wide applications in industries and other fields.

The electrolysis is employed in the isolation of large number of metals (Na, Al, Mg, Ca, Cu, etc.) and non-metals (Cl2, F2, etc.). And manufacture of compounds such as sodium hydroxide, heavy water & potassium permanganate.

Electrodeposition of metals is also based on electrolysis.

Electrolytic decomposition is the basis for a number of important extractive and manufacturing processes in modern industry. Caustic soda, an important chemical in the manufacture of paper, rayon, and photographic film, is produced by the electrolysis of a solution of common salt in water (see Alkalies). The reaction produces chlorine and sodium. The sodium in turn reacts with the water in the cell to yield caustic soda. The chlorine evolved is used in pulp and paper manufacture.

An important industrial use of electrolysis is in the electrolytic furnace, which is employed in the manufacture of aluminum, magnesium, and sodium. In this furnace the resistance of a charge of metallic salts is used to heat the charge until it becomes molten and ionizes. The metal is then deposited electrolytically.

Electrolytic methods are also employed in the refining of lead, tin, copper, gold, and silver. The advantage of extracting or refining metals by electrolytic processes is that the deposited metal is of great purity. Electroplating, another industrial application of electrolytic deposition, is used to deposit films of precious metals on base metals and to deposit metals and alloys, as strengthening or wear-resistant coating, on metal parts. Recent advances in electrochemistry include the development of new techniques for placing layers of material on electrodes to increase their efficiency and endurance. Electrodes made out of polymers are now also possible, through the discovery of polymers that can conduct electricity.

Electroplating is done to provide inert and attractive coating on metals.

The metals most frequently used as plating materials are Cu, Ni, Cr, Zn and noble metals like silver and gold.

It is going to play an important role in future as a source of energy.

Chemical composition of the crust[1]

The crust of the earth composed of three principal types of rocks igneous, sedimentary and metamorphic. The 8 elements make up almost 99% of the earth’s crust.

Oxygen is the most abundant element by weight and accounts for more than 90% of the volume of the crust. Next in the sequence is silicon.

In the most abundant element’s list, everyday common elements like carbon, cooper, zinc and nitrogen do not appear among the 10 most abundant elements.

Chemical Composition of the atmosphere[2]

The hydrosphere is composed of water, along with snow and ice. There is about 273 liters of water for each square cm of the earth’s surface. Of this water, 286.4 liters if ocean. 0.1 litres is freshwater and 4.5 litres is ice & snow. The earth’s atmosphere, is made up of a number of gases, which are

Nitrogen (N2)	78.1%
Oxygen (O2)	20.29%
CO2	0.3%
Water vapour	0.4%
Inert gases	0.95%
SO2, N2O, etc.	Variable

The N2 in the air, control the O2 in the air, as O2 is very reactive. Without N2, everything will be burning in the atmosphere. N2 also helps in plant growth & protein formation. CO2 is utilized by the plants to prepare food during the photosynthesis. Water vapour controls the evaporation of water from the bodies of plants & animals. Air is also required for burning and combustion. O2 is essential for respiration. The amount of O2, N2 and CO2 remains the same.

Petroleum and natural gas

The chemical composition of all petroleum or rock oil is principally hydrocarbons, although a few sulfur-containing and oxygen-containing compounds are usually present; the sulfur content varies from about 0.1 to 5 percent. Petroleum contains gaseous, liquid, and solid elements. The consistency of petroleum varies from liquid as thin as gasoline to liquid so thick that it will barely pour. Small quantities of gaseous compounds are usually dissolved in the liquid; when larger quantities of these compounds are present, the petroleum deposit is associated with a deposit of natural gas (see Gases, Fuel).

Three broad classes of crude petroleum exist: the paraffin types, the asphaltic types, and the mixed-base types. The paraffin types are composed of molecules in which the number of hydrogen atoms is always two more than twice the number of carbon atoms. The characteristic molecules in the asphaltic types are naphthenes, composed of twice as many hydrogen atoms as carbon atoms. In the mixed-base groups are both paraffin hydrocarbons and naphthenes

Formation

Petroleum is formed under the earth’s surface by the decomposition of marine organisms. The remains of tiny organisms that live in the sea—and, to a lesser extent, those of land organisms that are carried down to the sea in rivers and of plants that grow on the ocean bottoms—are enmeshed with the fine sands and silts that settle to the bottom in quiet sea basins. Such deposits, which are rich in organic materials, become the source rocks for the generation of crude oil. The process began many millions of years ago with the development of abundant life, and it continues to this day. The sediments grow thicker and sink into the seafloor under their own weight. As additional deposits pile up, the pressure on the ones below increases several thousand times, and the temperature rises by several hundred degrees. The mud and sand harden into shale and sandstone; carbonate precipitates and skeletal shells harden into limestone; and the remains of the dead organisms are transformed into crude oil and natural gas.

Once the petroleum forms, it flows upward in the earth’s crust because it has a lower density than the brines that saturate the interstices of the shales, sands, and carbonate rocks that constitute the crust of the earth. The crude oil and natural gas rise into the microscopic pores of the coarser sediments lying above. Frequently, the rising material encounters an impermeable shale or dense layer of rock that prevents further migration; the oil has become trapped, and a reservoir of petroleum is formed. A significant amount of the upward-migrating oil, however, does not encounter impermeable rock but instead flows out at the surface of the earth or onto the ocean floor. Surface deposits also include bituminous lakes and escaping natural gas.

Refining

Once oil has been produced from an oil field, it is treated with chemicals and heat to remove water and solids, and the natural gas is separated. The oil is then stored in a tank, or battery of tanks, and later transported to a refinery by truck, railroad tank car, barge, or pipeline. Large oil fields all have direct outlets to major, common-carrier pipelines.

Basic Distillation

The basic refining tool is the distillation unit. Crude oil begins to vaporize at a temperature somewhat less than that required to boil water. Hydrocarbons with the lowest molecular weight vaporize at the lowest temperatures, whereas successively higher temperatures are required to distill larger molecules. The first material to be distilled from crude oil is the gasoline fraction, followed in turn by naphtha and then by kerosene. The residue in the kettle, in the old still refineries, was then treated with caustic and sulfuric acid, and finally steam distilled thereafter. Lubricants and distillate fuel oils were obtained from the upper regions and waxes and asphalt from the lower regions of the distillation apparatus. In the later 19th century the gasoline and naphtha fractions were actually considered a nuisance because little need for them existed, and the demand for kerosene also began to decline because of the growing production of electricity and the use of electric lights. With the introduction of the automobile, however, the demand for gasoline suddenly burgeoned, and the need for greater supplies of crude oil increased accordingly.

Alternatives

In light of the reserves available and the dismal projections, it is apparent that alternative energy sources will be required to sustain the civilized societies of the world in the future. The options are indeed few, however, when the massive energy requirements of the industrial world come to be appreciated. Commercial oil shale recovery and the production of a synthetic crude oil have yet to be demonstrated successfully, and serious questions exist as to the competitiveness of production costs and production volumes that can be achieved by these potential new sources.

The various problems and potentials involved in such alternative sources as geothermal energy, solar energy, and nuclear energy are discussed in see Energy Supply, World. One of the alternative fuel that is capable of supplying the huge energy need of today’s world is coal, the availability of which in the U.S. and elsewhere throughout the world is well established. Associated with its projected increased utilization would be an increase in the use of coal-based electrical power to do more and more of the chores of industrialized nations. Adequate safeguards can perhaps be set on its use by modern engineering technology, with little increase in capital and operating costs. The last large-scale use of petroleum may thus occur before the end of the 20th century.

Use of ethanol as a blend and biofuels is catching pace nowadays.

Gaseous Fuels

Coal Gas

The most important coal-gasification processes aim chiefly at production of so-called pipeline quality gas, which is reasonably interchangeable with natural gas. Gas from coal, besides having pumping and heating specifications, must meet strict limits on content of carbon monoxide, sulfur, inert gases, and water. To meet these standards, most coal-gasification processes culminate with gas cleanup and methanation operations. Various hydrogasification processes, in which hydrogen reacts directly with coal to form methane, are used today; these processes bypass the indirect step of producing synthesis gas, hydrogen and carbon monoxide, before an upgrading yields methane. Other coal-gas processes include the carbon dioxide acceptor process, employing the lime-bearing material dolomite, and the molten salt process. These processes work indirectly to produce synthesis gas first. Other gases manufactured formerly from coal and coke, such as illumination gas and coke-oven gas, are of little or no importance today.

Producer and Blast-Furnace Gases

Producer gas is a form of water gas, a term applied to steam-process gases. It is made by burning low-grade fuel (such as lignite or bituminous coal) in a closed vessel, called a producer, while passing a continuous stream of steam and air through the producer. Because of the air present in the producer, the resulting gas is approximately 50 percent incombustible nitrogen and is low in fuel value, having only about 28 percent the heating value of coke-oven gas.

Blast-furnace gas, which results from the interaction of limestone, iron ore, and carbon in blast furnaces, has some heating value because of its carbon monoxide content but contains about 60 percent nitrogen. Enormous quantities are produced during the operation of furnaces. Most of this gas is consumed in heating the air blast and driving the compressors for the blast. The heating value of blast-furnace gas is about 16 percent of that of coke-oven gas. For a discussion of oil gas, made by the pyrolysis of petroleum hydrocarbons.

Natural Gas

A certain amount of natural gas almost always occurs in connection with oil deposits and is brought to the surface together with the oil when a well is drilled. Such gas is called casing-head gas. Certain wells, however, yield only natural gas.

Natural gas contains valuable organic elements that are important raw materials of the natural-gasoline and chemical industries. Before natural gas is used as fuel, heavy hydrocarbons such as butane, propane, and natural gasoline are extracted as liquids. The remaining gas constitutes so-called dry gas, which is piped to domestic and industrial consumers for use as fuels; dry gas, devoid of butane and propane, also occurs in nature. Composed of the lighter hydrocarbons methane and ethane, dry gas is used also in the manufacture of plastics, drugs, and dyes. Natural gas contains about 80% methane and 10% ethane, while rest is the other hydrocarbon gases. It is utilised as a domestic cooking gas, which is compressed and filled as liquefied petroleum gas (LPG) in the cylinders.

LPG

The Liquefied Petroleum Gas (LPG) is essentially liquid butane or propane (obtained from natural gas) or butane propane mix (obtained during refining of gas or cracked gas). The fuel is highly volatile, gaseous under ordinary atmospheric situations, highly combustible and forms an explosive mixture with air. To detect the gas leakage, a strong smelling substance (odorous organic sulphides known as mercaptans) are added. Except domestic use, the LPG can be utilised in agricultural, food processing, textile, metal and ceramic purposes. The compressed natural gas can be utilized as engine fuel for vehicles and trucks.

Gobar Gas

This gas is obtained by the gobar, which is subjected to anaerobic fermentation by a culture of microorganisms in closed tanks. The gas thus formed is mainly methane and CO2.The optimum temperature for the reaction is 35-55C.The residue is a excellent manure for the plant’s growth.

Performance of fuel

An octane rating scale has been developed to compare the performance of different mixtures of gasolines that might be used in automobile engines. A poor fuel such as heptanes, has been given an octane rating of zero while iso-octane has been given a rating of 100 on the octane scale and is known as the best fuel.

Octane number of a fuel is the percentage by volume of iso-octane in a mixture of iso-octane and the normal heptane that is equal to the fuel in knock characteristics under specified test conditions.

Chemical compounds are frequently added to petrol, to increase its efficiency as an engine fuel. One such additive is tetra ethyl lead. Organic phosphates are also introduced as additives.

Fuel cells

Fuel cells convert the energy of a fuel directly to electricity and supposed to be more efficient than the other methods of electricity generation.These electrical cells convert the energy from the combustion of fuels such as hydrogen, carbon monoxide or methane directly into electricity.A fuel cell uses the reaction of hydrogen with oxygen to from water and to supply electric power.The fuel cells can supply the electricity as long as reactants are supplied. So far 60-70 percent efficient fuel cells have been developed.

Fuel cells are free from pollution, and work is going on to reproduce electricity from fuel cells on commercial scale.

The phenomenon of radioactivity was discovered by the French scientist Henri Becquerel, in 1896. He noted that crystals of potassium uranyl sulphate, placed over a wrapped photographic plate even in total darkness, could produce background marks on the plate after its development. Marie and Plerre Curie in 1898 isolated the elements radium and polonium. Other such elements are uranium and thorium. Such elements are known as naturally occurring radioactive elements. The man-made elements, which are radioactive and exhibit artificial radioactivity. These are technetium, neptunium, curium and californium. The phenomenon of radioactivity is due to decay of unstable nuclei Naturally occurring radioactive elements undergo decay by emitting - alpha, beta, and gamma rays, thus producing stable, non-radioactive daughter element. When a radioactive nucleus emits an alpha particle, its atomic number is reduced by 2 and its mass number is reduced by four. When uranium 238 nucleus is bombarded with alpha particle, it produces throrium-234 nucleus. The activity of a radioactive element is measured by the rate at which it changes into its daughter element.

Half-Life

Half-life period is the time required for disintegration of one half of atoms of radioactive species initially present. The decay of some substances, such as uranium-238 and thorium-232, appears to continue indefinitely without detectable diminution of the decay rate per unit mass of the isotope (specific-decay rate). Other radioactive substances show a marked decrease in specific-decay rate with time. Among these is the isotope thorium-234 (originally called uranium X), which, after isolation from uranium, decays to half its original radioactive intensity within 25 days. Each individual radioactive substance has a characteristic decay period or half-life; because their half-lives are so long that decay is not appreciable within the observation period, the diminution of the specific-decay rate of some isotopes is not observable under present methods. Thorium-232, for example, has a half-life of 14 billion years.

Radioactive Decay Series

When uranium-238 decays by alpha emission, thorium-234 is formed; thorium-234 is a beta emitter and decays to form protactinium-234. Protactinium-234 in turn is a beta emitter, forming a new isotope of uranium, uranium-234. Uranium-234 decays by alpha emission to form thorium-230, which decays in turn by alpha emission to yield the predominant isotope, radium-226. This radioactive decay series, called the uranium-radium series, continues similarly through five more alpha emissions and four more beta emissions until the end product, a nonradioactive (stable) isotope of lead (element 82) of mass 206 is reached. Every element in the periodic table between uranium and lead is represented in this series, and each isotope is distinguishable by its characteristic half-life.

An interesting application of knowledge of radioactive elements is made in determining the age of the earth. One method of determining geologic time is based on the fact that in many uranium and thorium ores, all of which have been decaying since their formation, the alpha particles have been trapped (as helium atoms) in the interior of the rock. By accurately determining the relative amounts of helium, uranium, and thorium in the rock, the length of time during which the decay processes have been going on (the age of the rock) can be calculated. Another method is based on the determination of the ratio of uranium-238 to lead-206 or of thorium-232 to lead-208 in the rocks (that is, the ratios of concentration of the initial and final members of the decay series). These and other methods give values for the age of the earth of between 3 billion and 5 billion years.

The rate of radioactive decay can be measured by counting the number of particles emitted per unit using several instruments-scintillation counter, Wilson cloud chamber and Geiger Muller counter.

Transmutation is the conversion of one element into another, and is a dream of alchemists. A large number of transmutations have been carried out using the alpha particles, protons, deutrons and some heavier nuclei. Transmutant elements produced are carbon from beryllium, magnesium from sodium, carbon from nitrogen.

The first man-made radioisotopes are phosphorous silicon (14Si), nitrogen (7N). Several types of particle accelerators have been constructed to impart high energies to the sub atomic particles.

Synthetic elements are produced by the particle bombardment to the parent element to synthesize artificial elements such as technetium (from molybdenum), neptunium (from uranium), curium (from plutonium), and californium (from uranium).

Nuclear fission is a reaction, in which a heavy nucleus is broken up into two fragments of lighter nuclei and several neutrons. Atomic Bomb is based on the nuclear chain reaction, in nuclear fission.

In an atomic bomb, two or more pieces of fissionable material (uranium-235 or plutonium-239), each less than the critical mass, are brought together rapidly (*by means of a conventional explosive) so that, making one piece. Reactions starts with releasing large amount of energy.

In nuclear reactors, the nuclear fission reaction is a controlled one, and the energy released is harnessed.

A nuclear reactor consists of

• (a)   Fissionable material, (uranium enriched in U-235 (2-3%)
• (b)   Moderator (graphite or heavy water) to slow down the neutrons, thereby increasing the efficiency of their capture, and to bring about a fission reaction.
• (c)   Control rods made up of boron steel or cadmium is used to capture the neutrons, and to restrict the reaction and thus it remains a controlled one.

The large amount of energy released in the form of heat is converted into electrical energy.

Breeder reactors, is a facility in which fissionable isotope, which is enriched and used as a fuel in a nuclear reactor.

Ex:

• Uranium-238 is bombarded with fast neutrons to produce uranium-239, and later plutonium-239.
• Naturally more abundant thorium-232 breeds a fissionable isotope uranium-233

Nuclear fusion- two or more light nuclei combine to form a heavy nucleus, of helium. On the basis of fusion reaction, hydrogen or thermonuclear bomb is designed. The energy of the sun or other stars is believed to arise from the fusion of hydrogen nuclei to form helium.

A thermonuclear fusion reactor to generate a vast source of energy is still a technological challenge. The reaction is considered possible by the fusion of Deutrium nuclei into helium. Deutrium is available in plenty.

Hazards of Nuclear radiations

• The discharge of volatile radioactive isotopes into the atmosphere and the leakage of radioactive material into the water stream are hazardous.
• The radiations from radionucleides and neutrons have harmful biological effects. They may cause genetic mutations leading to skin cancer and leukemia.
• The radionucleides, such as iodine-131, ingested with food accidentally organs like thyroid glands, and get concentrated in the gland, & may cause severe damage to the thyroid gland.
• The extreme care is taken while working with radioisotopes.

Rocket Propellants

The rocket engines of the space vehicles are powered by the chemical propellants.

A propellant is a combination of an oxidizer and a fuel, which when ignited undergoes combustion to release the hot gases, through the nozzle of the rocket motor.

The passage of the gases through the nozzle provides the required thrust for the rocket to move forward.

The propellants are of three types:

Solid propellant is a blend of polymeric binder such as polyurethane or polybutadiene as fuel and ammonium perchlorate as oxidizer; with some other additives. Another solid propellant is a mixture of nitroglycerine and nitrogellulose. Nitrocellulose gel and nitroglycerine sets in as a solid mass. Solid propellants, once ignited, would burn with a pre-determined rate and cannot be regulated to stop or start again.

Liquid propellants have an oxidizer such as liquid oxygen, nitrogen tetroxide or nitric acid and a fuel such as kerosene, alcohol, hydrazines or liquid hydrogen. The liquid propellants give higher thrusts than solid propellants and it can be controlled by switching on and off the flow of propellant.

The hybrid rocket propellant consists of a solid fuel and a liquid oxidizers (e.g. liquid nitrogen tetroxide and acrylic rubber).

Some important rockets/booster propellants are given below-

• The Saturn booster rocket uses a combination of kerosene and liquid oxygen as the propellant for initial stage and liquid oxygen and liquid hydrogen for the upper stages.
• Titan ballastic missiles use hydrazine as fuel and nitrogen tetroxide as oxidizers.
• The US Space Shuttle uses liquid hydrogen-liquid oxygen with solid boosters at lower stages.
• The Proton rocket of Russia used liquid propellants made up of kerosene and liquid oxygen.
• Our rockets like SLV-3 and ASLV use composite solid propellants.
• The PSLV rocket uses a solid propellant in the first and the third stages, while the second and fourth stage uses liquid propellants.
• The liquid propellants are nitrogen tetroxide & UDMAH and nitrogen tetroxide and MMH for second and fourth stages of rockets respectively.

Superconductivity, phenomenon displayed by certain conductors that demonstrate no resistance to the flow of an electric current. Superconductors also exhibit strong diamagnetism; that is, they are repelled by magnetic fields. Superconductivity is manifested only below a certain critical temperature Tc and a critical magnetic field Hc, which vary with the material used. Before 1986, the highest Tcwas 23.2 K (-249.8° C/-417.6° F) in niobium-germanium compounds. Temperatures this low were achieved by use of liquid helium, an expensive, inefficient coolant. Ultra low-temperature operation places a severe constraint on the overall efficiency of a super-conducting machine. Thus, large-scale operation of such machines was not considered practical. But in 1986 discoveries at several universities and research centers began to radically alter this situation. Ceramic metal-oxide compounds containing rare-earth elements were found to be super conductive at temperatures high enough to permit using liquid nitrogen as a coolant. Because liquid nitrogen, at 77K (-196° C/-321° F), cools 20 times more effectively than liquid helium and is 10 times less expensive, a host of potential applications suddenly began to hold the promise of economic feasibility. In 1987 the composition of one of these super conducting compounds, with Tcof 94K (-179° C/-290° F), was revealed to be (Y0.6Ba0.4)2CuO4. It has since been shown that rare-earth elements are not an essential constituent, for in 1988 a thallium-barium-calcium copper oxide was discovered with a Tc of 125K (-148° C/-234° F). Superconductivity was first discovered in 1911 by the Dutch physicist Heike Kamerlingh Onnes, who observed no electrical resistance in mercury below 4.2 K (-268.8° C/-451.8° F).

Applications

Because of their lack of resistance, superconductors have been used to make electromagnets that generate large magnetic fields with no energy loss.

Superconducting magnets have been used in studies of materials and in the construction of powerful particle accelerators. Using the quantum effects of superconductivity, devices have been developed that measure electric current, voltage, and magnetic field with unprecedented sensitivity.

The discovery of better superconducting compounds is a significant step toward a far wider spectrum of applications, including faster computers with larger storage capacities, nuclear fusion reactors in which ionized gas is confined by magnetic fields, magnetic suspension of high-speed (“Maglev”) trains, and perhaps most important of all, more efficient generation and transmission of electric power.

Superconductivity at 77 Kelvin in liquid nitrogen is of great potential in technological application.

Possible applications are in electronics, building magnets, levitation transportation and power transmission.

Now research is more concentrated to do superconductivity at the room temperature.