Zusammenfassung der Ressource
C1.3 Metals And Their Uses
- C1.3.1 Extracting Metals
- Ores are naturally occurring rocks that provide a
starting point for the manufacture of metals.
- A metal ore is a rock containing a
metal, or a metal compound, in high
enough concentration to make it
economic to extract the metal.
- Ores are mined and may need to be concentrated
before the metal is extracted and purified.
- The economics of extraction may change over time;
as a metal becomes rarer, an ore may be used when
it was previously considered too expensive to mine.
- Unreactive metals are found as the
native metal but most metals are found
as compounds; requiring chemical
reactions to extract the metal.
- Metals less reactive than carbon
can be extracted from their
oxides by reduction with carbon.
- Metals more reactive than carbon are extracted
by electrolysis, an expensive process due to the
many stages and the energy required.
- Copper can be extracted from copper-rich
ores by smelting, then purified by electrolysis.
The supply of copper-rich ores is limited.
- There are ways to limit the environmental
impact of traditional mining.
- Phytomining is the process
of burning plants which
have absorbed metal
compounds to produce
ash. Bioleaching uses
bacteria to produce
leachate solutions that
contain metal compounds.
- Aluminium is extensively recycled
because less energy is needed than
to extract aluminium from its ore;
preserving limited resources and
energy, causing less damage to the
environment.
- C1.3.2 Alloys
- Iron from the blast furnace contains about
96% iron; the impurities make it brittle.
- Most iron is converted
into steels; alloys
which are mixtures of
iron and carbon.
- Alloys can be designed for
specific uses. Low-carbon
steels are easily shaped,
high-carbon steels are hard,
and stainless steels are
resistant to corrosion.
- Most metals in
everyday use are
alloys as pure
copper, gold, iron
and aluminium
are too soft for
many uses.
- C1.3.3 Properties And Uses Of Metals
- Transition metals, like other metals, are good
conductors and can be bent or hammered into
shape. They are useful as structural materials.
- Copper has properties making it useful for electrical
wiring and plumbing: good conductor of electricity and
heat; can be bent but is hard enough to be used to
make pipes or tanks and does not react with water.
- Low density and resistance to corrosion
make aluminium and titanium useful metals.