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Metals Revision

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Dr P.

on 29 May 2012

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Transcript of Metals Revision

Metals Obtaining them Uses Purification Iron Copper Aluminium and Titanium Native Ore Mining Concentration Reduction "a naturally occuring rock which contains sufficient metal compound to make it worth mining and extracting" Unreactive metals are found as the element (chemically uncombined) and only need purifying Can be very damaging to environment - animals and plants Creates jobs locally Extra traffic damages buildings Dust and noise pollution If ores don't contain much metal compound, they need to be concentrated so that waste material can be removed before the chemical extraction. The removal of oxygen from a metal oxide to form the metal. Typical reducing agents include carbon (coal) or reactive metals such as sodium (very expensive). Reactivity Series Metals low in the reactivity series are found native.
Metals in the middle of the series are formed by carbon reduction of metal oxides.
Metals high in the series are extracted by electrolysis (expensive as high temps and electricity needed Nearly three quarters of elements in the periodic table are metals They appear on the left hand side of the periodic table and in the middle. All metals conduct electricity and heat well. Most metals are hard, shiny, and have high melting points (especially transition metals). Chemical extraction produces metals which are often contaminated with impurities. Impurities make the metals less useful - properties affected
impure copper does not conduct as well
impure iron is brittle
impure titanium is brittle Copper ores smelted Impure copper purified by electrolysis Copper compounds extracted from low grade ores by:
bioleaching Resulting solutions containing copper compounds treated with reactive metals (displacement by scrap iron) to release copper metal Brassicas are plants which can extract copper compounds from the soil Lots of detail needed on this Ore is mainly iron (III) oxide. Blast furnace Carbon reducing agent Continuous process High temperatures Fe O 2 3 C + O CO 2 2 CO C 2 + 2CO 3CO + Fe O 3CO + 2Fe 2 2 3 3 2 3CO + 2Fe 3C + Fe O EQUATIONS Brittle pig iron Converted to the alloy, steel Low density Protected by inert layer of the metal oxide Don't corrode Al extracted by electrolysis, so expensive Ti extracted by reduction using sodium, so expensive Recycling therefore very important:
conserves resources
less energy used
metals don't corrode so can be used again and again Strength - building Electrical conductivity - electrical wiring Malleable - pipes Corrosion resistant - pipes, cutlery Ductile - wires Heat conduction - saucepans impure copper is made the positive electrode
pure copper collects at negative electrode But a very slow process overall they are heated with in air to form copper oxide
which is reduced to the metal by carbon Alloys mixtures of metals (and sometimes a small amount of carbon)
mixing metals blends their properties
alloys have more useful properties than pure metals pure metals such as copper, gold, iron and aluminium are too soft
mixing other elements can make them harder and more useful low carbon steel - easily shaped
high carbon steel is hard
stainless steel is resistant to corrosion in pure metals, layers of atoms can slide over one another in alloys, layers are disrupted and can no longer slide over one another Plants absorb metal compounds, and are then burned to produce ash that contains the metal compounds. Bacteria absorb metal compounds to give a solution rich in the metal compound
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