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