Extraction of Metals
A solid element or compound which occurs
in the Earth's crust is called a mineral.
A mineral which contains a high enough percentage of a metal
for economic extraction is called a metal ore.
Economic extraction means that the cost of
getting the metal out of the ore is sufficiently less than
the amount of money made by selling the metal.
common metal ores are oxides and
Sulfides are the oldest ores, formed in the Earth's history
when there was a lot of sulfur from volcanic activity.
Oxides formed later when photosynthesis in plants
released large amounts of oxygen into the atmosphere.
ore deposits are a finite
(there are only a certain amount of them)
(once used, they are gone and will not be replaced).
Many metals are obtained today from recycling
(melting and refining) scrap metals.
About half of the aluminium, copper, lead, steel and tin
which are used in the UK come from recycled scrap metal.
A metal above carbon in
may be extracted from its ore by electrolysis.
A metal below carbon in
the reactivity series (zinc to silver)
may be extracted from its ore by heating with carbon.
The metal is displaced from its non-metal anion
by the more reactive carbon.
Carbon is used because it is readily available and cheap
(coke or charcoal are both carbon).
The metal in the ore is said to be reduced by reaction with carbon.
Hydrogen may be used to reduce metals
which are lower than itself in the reactivity series,
but since it is more expensive than carbon
it is only used on a large scale for the extraction of tungsten,
to avoid the formation of tungsten carbide.
and platinum occur in the Earth as native
which means that they are found as the element, not the compound,
and so do not need to be reduced.
Silver and copper may also be found as native metal.
Links Search Questions
gcsescience.com Contents The Periodic Table Index Quizzes gcsescience.com
Copyright © 2012 Dr. Colin France. All Rights Reserved.