Production and Uses of Metals

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Production and Uses of Metals

• CHEMISTRY 2

Additional Science
Chapter 8
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Metallic minerals
The least reactive metals occur in an uncombined
form within the Earths crust.
The other metals exist as ores in combination
with other elements such as oxygen and sulphur.
Additional Science
Chapter 8
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The reactivity series of metals
Different metals have different reactivities. A
more reactive metal will remove oxygen from the
oxide of a less reactive metal when a mixture of
the two is heated.
When a mixture of powdered aluminium and
iron(III) oxide is ignited by a high temperature
fuse, molten iron is formed. This reaction is
called the thermit reaction and is used to weld
sections of railway track.
A mixture of aluminium and iron(III) oxide
reacting together
Additional Science
crucible
Chapter 8
railway track
railway track
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The reactivity series of metals
This table shows the reactivity series of common
metals, and how they are extracted from their
ores.
Reactivity Element Extraction method Reaction with acid
Strong K (Potassium) Electrolysis Too dangerous
Na (Sodium) Electrolysis Too dangerous
Ca (Calcium) Electrolysis Releases hydrogen and dilute hydrochloric acid.
Mg (Magnesium) Electrolysis Releases hydrogen and dilute hydrochloric acid.
Zn (Zinc) Chemical reduction Releases hydrogen and dilute hydrochloric acid.
Fe (Iron) Chemical reduction Releases hydrogen and dilute hydrochloric acid.
Sn (Tin) Chemical reduction Releases hydrogen and dilute hydrochloric acid.
Cu (Copper) Chemical reduction Doesnt release hydrogen and dilute hydrochloric acid.
Weak Ag (Silver) Chemical reduction Doesnt release hydrogen and dilute hydrochloric acid.
Additional Science
Chapter 8
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Extracting iron from its ore Chemical reduction
with carbon
1. Raw materials (iron ore, coke and limestone)
are added at the top of the furnace.
2. Blasts of hot air (which give the furnace its
name) are blown in near the bottom of the
furnace.
Load if iron ore, coke and limestone
3. Oxygen in the blasts of air reacts with coke
(carbon) to form carbon monoxide. 2C
O2 ? 2CO This reaction is very exothermic and
the temperature in the furnace reached 2000C.
Gas outlet
The blast furnace
1000C
4. As the carbon monoxide rises up the furnace,
it reacts with the iron ore (iron(III) oxide to
form iron. Fe2O3 3CO ? 2Fe 3CO2
1500C
5. Molten iron runs to the bottom of the furnace.
It is tapped off from time to time. 6. The
molten iron is used to make steel or poured into
moulds to solidify. The large chunks of iron
formed are called pigs so this metal is called
pig iron.
2000C
Molten slag (impurities)
Outlet for the slag
Outlet for molten iron
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Steel properties and uses
Iron from the blast furnace is very brittle
because it contains up to 4.5 carbon.
Most of this iron is converted to steel, which is
far more useful, by removing most of the carbon.
Mild steel contains approximately 0.5 carbon.
Hard steel contains up to 1.5 carbon.
Additional Science
It is possible to treat steel .
Chapter 8
Heat treatment
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Recycling steel
Saves up to 50 of energy costs
Helps to conserve iron ore
Cuts down the emission of greenhouse gases
Additional Science
Chapter 8
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Electrolysis background
Additional Science
Chapter 8

• Electrolysis is a chemical reaction. Current
  enters the electrolyte via two solid conductors
  called electrodes.

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Electrolysis background
ion
ion-
ion
ion-
Additional Science
ion
ion-
ion
ion-
Chapter 8

• The anode is the positive electrode, and the
  cathode is the negative electrode.

The positive ions (cations) move towards the
negative electrode, and the negative ions
(anions) move towards the positive electrodes.
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Electrolysis extraction of reactive metals
Remove impurities by chemical method
Bauxite a rock containing aluminium
Aluminium oxide powder (alumina), with a very
high melting point
Electrolysis of aluminium oxide (alumina)
crust of solidified electrolyte
1. Aluminium oxide is dissolved in molten
cryolite (about 950C).
carbon anodes
2. Oxygen gas is formed at the carbon anodes, and
at that high temperature the anodes react with
oxygen, burning away and having to be replaced
from time to time.
aluminium oxide in molten cryolite
Additional Science
Chapter 8
Molten aluminium
tap hole
3. Aluminium in the form of a molten metal forms
at the cathode.
4. The tap hole is used to collect the aluminium,
the crust needs to be broken to add more
aluminium oxide.
insulated cell casing
carbon lining to cell acting as the cathode
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The equations for the reaction
Positive aluminium ions are attracted to the
negative cathode, where they gain electrons and
form aluminium metal.
Additional Science
Negative oxide ions are attracted to the positive
anode, where they lose electrons and form oxygen
gas.
Chapter 8
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Locating aluminium works
Additional Science
Chapter 8
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Properties of aluminium
light
strong
density of 2.7g/cm3
resistant to corrosion
layer of aluminium oxide (this prevents corrosion
even though the metal is very reactive)
Using aluminium
Additional Science
Use Reason
1. High voltage power cables for the National Grid Light, resistant to corrosion
2. Saucepans and kitchen foil Good conductor of heat, non toxic
3. Window frames and greenhouses Strong and light
4. Drinks cans Strong and non toxic
5. Aeroplane and car bodies Strong and resistant to corrosion
Chapter 8
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Properties of copper
excellent conductor of electricity and heat
malleable
ductile
non toxic
Use of copper
Additional Science
Use Reason
1. Wires in electrical circuits Good conductor of heat
2. Saucepans Good conductor of heat and non toxic
3. Jewellery Malleable and ductile, attractive colour and lustre
4. Water pipes Non toxic and malleable
5. Produces the alloy bronze (copper tin) and brass (copper zinc)
Chapter 8
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Properties of titanium
good conductor of heat and electricity
light
strong
tough
high melting point
non toxic
low density
non corrosive
Using titanium
Additional Science
Use Reason
1. Aircraft industry Light, tough, non corrosive
2. Surgical equipment Light, tough, non corrosive
3. Artificial joints, plates for bone fractures Non toxic, light, tough, non corrosive
4. Jewellery Non toxic
5. Titanium dioxide is the basis of white paint.
Chapter 8
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The consequences of metal extraction
Disadvantages
Advantages
When the ore runs out, the mine workings may be
abandoned causing a deterioration of the
landscape.
Extraction and processing of minerals creates
employment.
Importing metals is very expensive for the
country.
Sometimes less useful and toxic metals are found
with the ones that are needed.
Important for the economy (Economic boom in the
UK during Industrial Revolution).
Additional Science
Fluctuations in the cost of metals can affect the
economy.
Chapter 8
A lot of electricity is needed to produce
aluminium.
Processing minerals have a detrimental effect on
the environment.
Many minerals are sulphides produce sulphur
dioxide (the gas that causes acid rain).