Tamilnadu Samacheer Kalvi 12th Chemistry Notes Chapter 1 Metallurgy Notes
Metallurgy: Metallurgy relates to the science and technology of metals. Metallurgy helps to study the various steps involved in the extraction of metal and the chemical principles behind these processes.
Mineral: A naturally occurring substance obtained by mining which contains the metal in free state or in the form of compounds like oxides, sulphides etc. is called a mineral.
Ore: Minerals that contains a high percentage of metal, from which it can be extracted conveniently and economically are called ores.
Gangue: Ores are associated with non-metallic impurities, rocky materials and siliceous matter which are collectively known as gangue.
Roasting: Roasting is the method, usually applied for the conversion of sulphide ores into their oxides. In this method, the concentrated ore is oxidized by heating it with excess of oxygen in a suitable furnace below the melting point of the metal.
Calcination: It is the process in which the concentrated ore is strongly heated in the absence of air. Here ore is converted into their oxides.
Smelting: It is the process of reducing the roasting metallic oxide to metal in molten condition.
Blistered copper: The solidified copper obtained after the reduction of copper matte has blistered appearance. This is called blistered copper.
Ellingham diagram: The graphical representation of variation of the standard Gibbs free energy of reaction for the formation of various metal oxides with temperature is called Ellingham diagram.
Distillation: In this method, the impure metal is heated to evaporate and the vapours are condensed to get pure metal.
Liquation: This method is employed to remove the impurities with high melting points from metals having relatively low melting points such as tin.
Electrolytic refining: The crude metal is refined by electrolysis. It is carried out in an electrolytic cell containing aqueous solution of the salts of the metal of interest. The rods of impure metal are used as anode and thin strips of pure metal are used as cathode.
Application of Aluminium (Al): Aluminium is the most abundant metal and is a good conductor of electricity and heat. It also resists corrosion. The following are some of its applications:
- Many heat exchangers/sinks and our day to day cooking vessels are made of aluminium.
- It is used as wraps (aluminium foils) and is used in packing materials for food items.
- Aluminium is not very strong, However, its alloys with copper, manganese, magnesium and silicon are light weight and strong and they are used in design of aeroplanes and other forms of transport.
- As Aluminium shows high resistance to corrosion, it is used in the design of chemical reactors, medical equipments, refrigeration units and gas pipelines.
- Aluminium is a good electrical conductor and cheap, hence used in electrical overhead and electric cables with steel core for strength.
Application of Zinc (Zn):
- Metallic zinc is used in galvanising metals such as iron and steel structures to protect them from rusting and corrosion.
- Zinc is also used to produce die-castings in the automobile, electrical and hardware industries.
- Zinc oxide is used in the manufacture of many products such as paints, rubber, cosmetics, pharmaceuticals, plastics, inks, batteries, textiles and electrical equipment. Zinc sulphide is used in making luminous paints, fluorescent lights and x-ray screens.
- Brass, an alloy of zinc is used in water valves and communication equipment, as it is highly resistant to corrosion.
Application of Iron (Fe):
- Iron is one of the most useful metals and its alloys are used everywhere including bridges, electricity pylons, bicycle chains, cutting tools and rifle barrels.
- Cast iron is used to make pipes, valves, pump stoves, etc.
- Magnets can be made of iron and its alloys and compounds.
- An important alloy of iron is stainless steel, and it is very resistant to corrosion. It is used in architecture, bearings, cutlery, surgical instruments and jewellery. Nickel steel is used for making cables, automobiles and aeroplane parts. Chrome steels are used for manufacturing cutting tools and crushing machines.
Application of Copper (Cu):
- Copper is the first metal used by the humans and extended use of its alloy bronze resulted in a new era, ’ Bronze age ’.
- Copper is used for making coins and ornaments along with gold and other metals.
- Copper and its alloys are used for making wires, water pipes and other electrical parts.
Application of Gold (Au):
- Gold, one of the expensive and precious metals. It is used for coinage, and has been used as standard for monetary systems in some countries.
- It is used extensively in j ewellery in its alloy form with copper. It is also used in electroplating to cover other metals with a thin layer of gold which are used in watches, artificial limb joints, cheap jewellery, dental fillings and electrical connectors.
- Gold nanoparticles are also used for increasing the efficiency of solar cells and also used as catalysts.