Native metals & Ores
Native metals are very unreactive
metals that are found as the
elements themselves.
These are silver, gold and platinum.
Minerals and rocks with enough
metal or metal compound to make it
economic to extract are called ores.
Alloys vs pure metals
Pure metals (b) are soft because
the layers of atoms can slide when
a force is applied. In an alloy (a
mixture of a metal and another
element), the atoms are of
different size so the layers are
distorted and cannot slide as easily.
Alloys (a) are therefore stronger
than pure metals.
Reduction
Electrolysis
Metals that are less reactive than carbon can be extracted from metal oxides
using carbon. Carbon will remove the oxygen and the metal will be left behind.
This is called reduction.
Iron is extracted inside the Blast furnace. Coke (carbon), limestone and iron
oxide are heated inside the furnace. Limestone reacts with the impurities and
forms slag. Coke reacts with oxygen first and then iron oxide to form iron and
carbon dioxide. The iron produced (called pig iron or cast iron) is brittle as it
contains too much carbon.
C + O2 -> CO2
CO2 + C -> 2CO
Fe2O3 + 3CO -> 2Fe + 3CO2
Metals that are more reactive
than carbon, are extracted from
their molten compounds using
electrolysis – using electricity to
split a compound. Large amounts
of energy are needed for
electrolysis which makes the
process expensive.
Steels
Titanium & Aluminium
Iron from the blast furnace contains about 96% iron. The 4% impurities make it brittle and so it
has limited uses. Some of the carbon is removed by blowing oxygen through the iron from the
blast furnace. The oxygen reacts with the carbon and forms CO2.
This leaves either low-carbon steel which is easily shaped and used to make car bodies,
machinery or ships or
high-carbon steel which is hard and strong but brittle and used to make tools.
Stainless steel is iron alloyed with chromium and nickel. It is corrosion resistant and used to
make cutlery, sinks and cooking utensils.
Recycling metals
Metals are non-renewable resources and unless we recycle metal objects, we will run out of
ores soon. Recycling also saves 95% energy and prevents new mines being opened.
Both metals are expensive as their
extraction process is long, requires
large amounts of energy and uses
expensive substances such as argon
and magnesium.
Titanium and aluminium alloys are
both corrosion resistant, very
strong and have a low density.
Titanium is used for hip
replacements, racing bikes and
space vehicles.
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