Transcript Slide 1 - Aldercar High School

Metals
Elements found in the Earth’s crust
Metals make up a relatively small proportion of the
Earth’s crust and are normally found in rocks as ores
46%
Oxygen
28%
Silicon
Aluminium
8%
5%
Iron
4%
Calcium
3%
Sodium
Magnesium
2%
Potassium
2%
Titanium
0.5%
Hydrogen
0.5%
All other elements1%
Most metals are found as ores
Bauxite –
aluminium oxide
(Al2O3)
Haematite –
iron oxide
(Fe2O3)
Malachite –
copper carbonate
(CuCO3)
In ores, the metal or metal compound is concentrated
enough to make it economic to extract the metal.
Some unreactive metals such as
gold can be found as the metal
itself – chemical separation is not
needed.
The method used to extract a metal from its ore
depends on the reactivity of the metal.
Most
reactive
Least
reactive
K
Na
Ca
Mg
Al
C
Zn
Fe
Sn
Pb
H
Cu
Ag
Au
Pt
Very reactive metals – extracted
using electrolysis
More reactive metals – usually
extracted by reduction – heating with
carbon to remove oxygen
Unreactive metals – little or
no extraction needed
Sometimes non-metals are included for reference.
Using the reactivity series, decide which items would be
most corroded.
Gold ring
Iron sword
Copper pin
Silver bracelet
Match the material to the use given the property.
Steel
Cast iron
Pure Iron
The extraction of iron – reduction in the blast furnace
Raw materials
ron ore (haematite)
I_______
oke
C____
L________
imestone
hot waste gases
iron oxide + carbon (coke)
iron + carbon dioxide
a reduction (loss of
oxygen) – the iron oxide is
reduced to iron metal
hot air
molten iron
1500oC
hot air
molten slag
Blast furnaces (for extracting iron) at Port Talbot
Steel
Iron from the blast furnace (cast iron) is brittle since it
contains about 4% carbon. It therefore has limited uses.
Similarly pure iron (wrought iron) is too soft for many uses.
Therefore most iron is
converted into steel.
Steel is basically iron with
up to 1.5% carbon.
Many other metals can
be added to make alloy
steels with a wide range
of properties.
Iron from the blast
furnace being
converted into steel
Low carbon
steel (mild
steel) is easily
shaped
The Angel of the
North is made of a
steel alloy – iron
combined with a
small amount of
copper
Stainless steel (iron
with about 15%
chromium) is perfect
for cutlery and razor
blades etc.
Stainless steel doesn’t
rust.
Metals are malleable
They can be hammered or bent into shape
Most pure metals have their atoms arranged in a
regular pattern and the layers of atoms can easily
slide over one another when a force is applied.
Force causes layers of
atoms to slide over one
another
Alloys are harder than pure metals
Alloys are mixtures of metals (or in the case of some
steels iron mixed with carbon). They are stronger than
pure metals.
The different sized atoms of
other metals stop the layers
sliding over one another
Copper
Malachite –
copper ore
Polished
malachite
Copper is a good heat and electrical conductor and
used for saucepans and electrical wire.
Since it is an unreactive metal it is also used for water
pipes and coinage.
The outside of the
Statue of Liberty is
made from copper.
Over time, the colour
has changed as the
copper has
weathered.
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.
Open cast mining of bauxite in Australia
Open cast mining for metal ores
What effect does this have on
the environment?
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.
Titanium
Like aluminium, titanium is an
extremely useful metal because it is
light, strong and resists corrosion.
It was used in the manufacture
of Concorde
Titanium ore
….. and is used in artificial hip
joints
The transition metals
Sc
Ti
V
Cr
Mn Fe Co Ni
These are found in the
middle block of the
Periodic Table
Cu Zn
They are useful metals and have typical metallic properties:
Good conductors of heat and electricity
High melting point
Strong
Malleable
Recycling metals
Six billion aluminium cans are made each
year – this is enough to reach to the moon
and back!
It takes the same amount of energy to make one new
aluminium can as it does to make twenty recycled cans!
So recycling metals such as aluminium:
Saves energy
Protects the environment – less rain forest has
to be cut down to dig out metal ores
Conserves the limited supplies of metal
ores
Reduces the amount of waste sent to landfill
sites
Smart alloys
After they are bent or deformed,
these alloys regain their original
shape – they have a shape
memory.
They have many uses
e.g.
Dental braces
The dental brace pulls
the teeth into the right
position as it warms
up!
Opening up collapsed arteries
Spectacle frames
Spectacle frames made of ‘smart
alloys’ return quickly to their
original shape after being bent.