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Aluminium Extraction and Uses http://www.youtube.com/watch?v= WaSwimvCGA8 Why are aluminium alloys used for the following? Aluminium Aluminium is the most common metal in the Earth's crust. Aluminium is extracted from the ore bauxite However it is a reactive metal (high in the reactivity series) and has to be extracted using electrolysis (passing electricity through the molten ore). Because lots of energy is needed and there are several stages to the process, aluminium is relatively expensive despite being a common metal. Aluminium Mining • Bauxite is a red mineral made of aluminium oxide and iron oxides. • Bauxite is mined in various places, e.g. Russia, Jamaica Open cast mining of bauxite in Australia Open cast mining for metal ores What effect does this have on the environment? Extracting aluminium • Aluminium is more reactive than carbon. • So carbon will not reduce aluminium oxide. • Aluminium cannot be extracted in a blast furnace. • Aluminium is extracted using electricity in a process called electrolysis. Bauxite Purification • Bauxite is heated with sodium hydroxide. • This dissolves the aluminium oxide but not the other minerals. • The residue is filtered off and disposed of. ALUMINIUM - ELECTROLYSIS flow of electrons +ve electrode -ve electrode -ve ions +ve ions ALUMINIUM - ELECTROLYSIS Problems Very high temperature needed to melt aluminium oxide to get electrolysis to work Lots of electricity is needed to split the Aluminium and Oxygen up This makes aluminium expensive – so cans are recycled Uses of aluminium Like most metals, pure aluminium is not used very much – it is usually made into alloys. Alloys of aluminium have low density and high strength, vital for the aerospace industry. Aluminium alloys were used to make the external fuel tanks of the space shuttle. Because of its low density and good electrical conductivity, aluminium is used in overhead power cables. Although aluminium is a reactive metal it is normally covered with a protective oxide layer and doesn’t corrode easily. Uses of aluminium • • • • • • • • • • • Power cables Saucepans Aeroplanes Bicycles Cars Battleships Cooking foil Cans Space blankets Statues Window frames • • • • • • • • • • • Light Light, unreactive Light Light, doesn’t rust Light, doesn’t rust Light, radar quiet Reflective, unreactive Unreactive Reflective Unreactive Unreactive
