Download Aluminium - School

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
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Power cables
Saucepans
Aeroplanes
Bicycles
Cars
Battleships
Cooking foil
Cans
Space blankets
Statues
Window frames
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Light
Light, unreactive
Light
Light, doesn’t rust
Light, doesn’t rust
Light, radar quiet
Reflective, unreactive
Unreactive
Reflective
Unreactive
Unreactive