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Introduction |
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Earth is an abundant source of material. Man has intensively studied the properties of these materials extensively and found new methods of using them. The air we breathe, the water we drink, stones and rocks, almost everything that is around us, are all useful to man for some purpose or the other. These materials are distributed in the atmosphere, lithosphere, and hydrosphere. Oxygen, Nitrogen and Carbon di oxide are found in the atmosphere. Common salt and various other salts of sodium, magnesium and calcium are found dissolved in water bodies, like the oceans, rivers and lakes. |
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Characteristics of Metals |
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One can easily differentiate between metals and non-metals based on their placement on the Periodic Table of the Elements. The metals are elements (with the exception of hydrogen) that are found to the left of a group of elements referred to as the metalloids. The metalloids are a group of elements which have properties similar to both the metals and non-metals. These metalloids are: Boron, silicon, germanium, arsenic, antimony, tellurium and astatine. |
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Electronic Nature of Metals |
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Metals are the elements which form positive ions by losing electrons, while non-metals always gain electrons. All metals (except hydrogen) form positive ions by loosing electrons. Metals have 1 to 3 electrons in the outermost shell of their atom and non-metals have 4 to 8 electrons in the outermost shell. Atomic number of aluminium is 13, so the electronic configuration of Al is 2, 8, and 3. Aluminium has 3 electrons in the valence shell. |
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The Various Kinds of Metals |
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The Various Kinds of Metals are as shown below:
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Properties of Metals |
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Physical State : Metals are solids at room temp with the exception of mercury and gallium which are liquids at room temp. |
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Summary of the Reaction of Metals with Air Water and Acids |
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The Reactivity Series of Metals |
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Differences between Metals and Non-metals |
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Minerals and Ores |
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Metals and their compounds are found in earth as natural elements known as minerals. Ores are minerals from which metals are extracted at low cost with minimum effort. Ores contains metal compounds with a percentage of impurities. All the ores are minerals, but all the minerals are not ores. |
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Metallurgy |
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Metallurgy is a domain of Material Science and Material Engineering. It is a study of the physical and chemical behavior of metallic elements and their mixtures, called alloys. Metallurgists study the microscopic mechanisms that cause a metal or alloy to behave in the way that it does, the changes that occur at the atomic level, that affect the metal's (or alloy's) macroscopic properties. The various processes involved in the extraction of metals from their ores and refining are known as metallurgy. |
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Concentration of Ore - Ore Dressing |
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Ore is a impure metal containing large amount of sand and rocky material. The impurities like sand, rocky materials, limestone, mica etc present in the ore is called gangue or matrix. The substance added flux to the ore to remove the matrix results in the formation of a fusible compound called slag. When the matrix is removed we get the concentrated ore. At first the ore is crushed to powder. The pulverized ore is separated by hydraulic washing, froth-floatation process, magnetic or chemical process, depending on the nature of the ore and its impurities. Concentration of the ore is also known as dressing of the ore or enrichment of ore. |
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Conversion of Concentrated Ore to Oxide and Reduction |
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A concentrate is a purified ore. It is converted to oxide either by roasting or calcination. The differences between roasting and calcination is given below:
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Refining of the Metal |
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Purification of the metal is the last step in metallurgy. Refining is based on the difference between the properties of metals and their impurities. |
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Metallurgy - Special Methods of Refining Metals |
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This method is used for obtaining ultra pure metals like germanium, silicon and gallium. |
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Metallurgy of Aluminum |
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Properties and Uses of Aluminium |
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* A bluish white metal. Light but strong and has a low density
* Resistant to corrosion and can be easily bent and shaped |
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Aluminium - Points to Remember |
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* The ore of aluminium is bauxite.
* The main chemical in bauxite is aluminium oxide (alumina for short).
* Aluminium is a very reactive metal. It is too reactive to obtain by displacement. Electrolytic reduction has to be used.
* The alumina has to be in the liquid state so that the ions from which it is made are free to move around and they can be attracted to the electrodes. |
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Metallurgy of Iron |
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Properties of Iron |
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Pure iron is a grey white metals. It appears to be brown due to rusting. It is malleable, ductile and magnetic. A good conductor of heat and electricity. Iron has a high density and high melting point. |
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Corrosion of Iron |
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Iron (or steel) corrodes more quickly than most other transition metals and readily does so in the presence of both oxygen (in air) and water to form an iron oxide. Rusting is speeded up in the presence of salt solution. |
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Alloys |
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An alloy is a mixture of two or more metals fused together in molten state. Metals when melted tend to dissolve in one another forming alloys. The various properties of a metal like malleability, ductility, strength, hardness, resistance to corrosion and appearance can be improved by mixing with other metals. Alloys have properties different from its constituents. |
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Metals in the Living System |
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Traces of metal is necessary for the human and animal system to function efficiently. Some of the important metals required are iron, copper, zinc, sodium and potassium. |
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Non Metals - Introduction |
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Non-metals are the elements in groups 14-18 of the periodic table. Non-metals are not able to conduct electricity or heat very well. As opposed to metals, non-metallic elements are very brittle, and cannot be rolled into wires or pounded into sheets. The non-metals exist in two of the three states of matter at room temperature: gases (oxygen) and solids (carbon). The non-metals have no metallic luster, and do not reflect light. |
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Hydrogen |
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Robert Boyle prepared hydrogen in 1672, by treating iron with sulphuric acid, but he could not decipher its basic nature. The credit of the discovery of hydrogen goes to the British chemist Henry Cavendish. He prepared the gas by the action of dil HCl with zinc in 1766. He established its elementary character and proved that when hydrogen burns in air it forms water. |
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Properties of Hydrogen |
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Hydrogen is the lightest element. It is by far the most abundant element in the universe and makes up about 90% of the universe by weight. Hydrogen as water (H2O) is absolutely essential to life and it is present in all organic compounds. |
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Uses of Hydrogen |
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The hydrogenation of oils to produce edible fats, of coal to form synthetic petroleum, and of petroleum oils to enrich the petrol fraction requires large amounts of hydrogen. |
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Ammonia |
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Ammonia was known to mankind since a long period, as it was produced in nature by putrefying and ammonifying bacteria. |
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Laboratory Preparation of Ammonia |
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For use in the laboratory, ammonia is prepared by heating an ammonium salt with a strong base. It can also be prepared by reacting a metal nitride with water. All ammonium salts heated with alkali evolve ammonia. Ammonium nitrate is not used in laboratory preparation, since it is explosive in nature and may decompose forming nitrous oxide and water vapour. |
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Manufacture of Ammonia Habers Process |
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Ammonia is prepared commercially in vast quantities. The major method of production is the Haber process invented by Fritz Haber, in which nitrogen is combined directly with hydrogen at high temperatures and pressures in the presence of a catalyst. |
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Properties of Ammonia |
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* Colourless
* Strong pungent smell
* Slight alkaline taste
* Non-poisonous Fatal in large doses |
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Sulphur |
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* Sulphur was initially called brimstone
* Free sulphur 'gandhaka' was known in India 3000 years ago
* It was used in fumigation, medicines and bleaching by Aryans, Greeks and Romans
* In 1777, Lavoisier was the first to recognize the basic nature of sulphur |
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Extraction of Sulphur - Frasch Process |
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Sulphur has a low melting point of about 112oC - 115oC |
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Allotropy in Sulphur |
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A chemical element is said to exhibit allotropy when it occurs in two or more free forms in the same physical state; the forms are called allotropes. Allotropes generally differ in physical properties such as color and hardness; they may also differ in molecular structure or chemical activity, but are usually alike in most chemical properties. Diamond and graphite are two allotropes of the element carbon. Ozone is a chemically active tri atomic allotrope of the element oxygen. Phosphorus, sulphur, and tin also exhibit allotropy. Many metals have allotropic crystalline forms that are stable at different temperatures. |
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Effect of Heat on Sulphur |
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* Heat on sulphur is a physical change.
* When heated, it undergoes a series of changes in colour, form and viscosity at various temp. |
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Uses of Sulphur |
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* The most important use of sulphur is in the manufacture of sulphur compounds, such as sulphuric acid, sulphites, sulphates, and sulphur dioxide.
* Medicinally, it has assumed importance because of its widespread use in sulpha drugs and in many skin ointments.
* Sulphur is also employed in the production of matches, vulcanized rubber, dyes, and gunpowder. |
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Sulphur Dioxide |
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* Sulphur dioxide was known from ancient times and Romans used it as a general cleansing agent.
* In 1770 , J.Priestly prepared the gas by the action of hot conc. Sulphuric acid on mercury and called it sulphurous acid. |
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Properties of Sulphur Dioxide |
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Sulphur dioxide 'SO2' a colorless gas with a pungent and suffocating odor. It is readily soluble in cold water, sparingly soluble in hot water, and soluble in alcohol, acetic acid, and sulfuric acid. |
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Uses of Sulphur Dioxide |
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* It is a powerful germicide and insecticide and hence it is used a household fumigant.
* It can bleach delicate fibres.
* It undergoes easy liquefaction and vaporization and hence it is used as refrigerent in cold storage plants. |
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Adverse Effect of Sulphur Dioxide on Environment |
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Sulphur dioxide is a dangerous air pollutant because of its corrosive properties; it irritates the eyes, nose, and lungs. It is produced by combustion of coal, fuel oil, and gasoline, since these fuels contain sulphur. The sulphur content of a fuel can be reduced by refining, so that less sulphur dioxide is emitted when the fuel is burned. Sulphur dioxide emitted into the atmosphere by industrial processes is ultimately converted into dilute sulphurous acid, returning to Earth as acid rain. For this reason, sulphur dioxide is a major cause of air pollution. |
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Sulphuric Acid |
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Sulphuric acid, H2SO4 is a colorless, odorless, extremely corrosive, oily liquid. It was initially called oil of vitriol. |
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Contact Process |
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Sulphuric acid is prepared by contact process all over the world. Preparation of sulphuric acid by contact process is based upon the catalytic oxidation of SO2 to SO3. |
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Properties of Sulphuric Acid |
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* Colourless and Odourless
* Slight sour taste
* Dense, oily, hygroscopic liquid
* Conc acid is highly corrosive |
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Uses of Sulphuric acid |
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* In the manufacture of fertilizers, ammonium phosphate and calcium super phosphate.
* In the manufacture of rayon and nylon and also in the preparation of dyes and drugs from coal tar derivatives.
* In the manufacture of the explosives such as Tri-nitro toluene , Tri-nitro glycerine and picric acid. |
