c6
metal ores
rock which contains enough metal to make it economically worthwhile extracting the metal from it
often the oxide of the metal
the main aluminium ore is bauxite, aluminium oxide
extracting metals chemically
by reduction or electrolysis
some ores may have to be concentrated before the metal extracted - getting rid of unwanted rocky material
electrolysis can also purify extracted metal
some metals extracted from their ores using displacement reactions
or biological methods
extraction through reduction
metal can be extracted from its ore chemically by reduction using carbon
when an ore is reduced, oxygen is removed from it
eg 2CuO + C --> 2Cu + CO2
position of the metal in the reactivity series determines whether it can be extracted by reduction with carbon
metals higher than carbon have to extracted through electrolysis which is expensive
metals below carbon can be extracted through reduction using carbon
carbon can only take oxygen away from metals which are less reactive than carbon itself
extraction through electrolysis
metals more reactive than carbon are extracted through electrolysis of molten compounds
once metal is melted an electric current is passed through it
metal is discharged at the cathode
non metal at the anoode
electricity is expensive, more expensive than reduction with carbon
purification of copper
easily extracted by reduction with carbon
ore is heated in a furnace - smelting
copper produced this way is impure, so it doesn't conduct electricity well
not useful because copper is used for electrical wiring
electrolysis purifies it, producing pure copper, a much better conductor
electrolyte is copper sulfate containing Cu2+ ions
cathode starts as a thin piece of pure copper and more pure copper adds to it
anode is a big lump of impure copper which will dissolve
biological extraction
supply of metal rich ores eg copper ore is limited, but demand for lots of metals is growing, may lead to shortages in the future
bioleaching : uses bacteria to separate metal from their ores, eg copper can be separated from copper sulfide this way
bacteria get energy from bonds between atoms in the ore, separating out the metal from the ore
the leachate (solution made in the process) contains metal ions, can be extracted by electrolysis or displacement with a more reactive metal
phytoextraction : growing plants in soil that contains metal compounds, plants can't use or get rid of the metals so gradually build up in the leaves
plants can be harvested, dried and burned in a furnace, ash contains metal compounds which from which the meta can be extracted by electrolysis or displacement reactions
traditional mining are damaging to environment, these have smaller impact but are slow
alloys
mixture of two or more different metals
or a mixture of a metal and non-metal
different properties to metals made from so often more useful than pure metal
steel
alloy of iron and carbon
harder than iron, stronger than iron as long as the amount of carbon is not greater than 1%
iron on its own will rust quickly, steel less likely to rust, bridges, cutlery, engine parts, saucepans all made of steel
brass
alloy of copper and zinc
most properties are a mixture of those of copper and zinc, brass is harder than both
used for making bass instruments like trumpets, as for fixtures and fittings like screws and doorknobs
bronze
alloy of copper and tin
harder and stronger than tin, more resistant to corrosion than both
used to make springs, motor bearings, bells and sculptures
solder
usually alloy of lead and tin
unlike pure materials, no definite melting point, gradually solidifies as it cools
useful for joining metal things together as easily worked, eg connecting components in electronic circuits
low melting point, can melt solder without deforming other components in the circuit
duralumin
94% aluminium, 4% copper, 1% magnesium and small amounts of manganese
low density, very light, much stronger than aluminium
strong and light, good for making parts of aeroplanes