Download Manufacturing Material Information Sheet

Manufacturing Material Information Sheet
Iron and Aluminium
Iron and aluminium are very common metals in the Earth’s crust. They are both found in the
form of compounds often-called minerals and can be part of rock crystals. Iron rich soils like
the soils in central Australia are red in colour. While iron and aluminium are a significant
component of the Earth’s crust, to process it requires high concentrations. High
concentrations of iron compounds are called iron ore. In Australia the high concentrations of
aluminium compounds are in minerals called bauxite. These minerals are extracted from vast
open cut mines. They must be transported to the coast where they are loaded onto bulk
carriers (type of ship) and shipped to a port where the mineral will be processed into metal.
Chemical reactions
To produce iron from iron ore two chemical reactions are required inside a blast furnace
operating at 2000 C. The raw materials required to produce iron are iron ore and coke.
Oxygen is needed as part of the reaction. Limestone or another chemical is added to
remove the bulk of the impurities. Coke is a form of processed coal. Coke is light and porous
containing a lot of air and able to burn at very high temperatures. Australia is a major
exporter of both iron ore and coke.
o
The two chemical reactions are:
2 C + O → 2 CO and
2
Fe O + 3 CO → 2 Fe + 3 CO
2
3
2
In the first reaction the coke (C) combines with oxygen (O ) to produce carbon monoxide
(CO). The carbon monoxide at 2000 C reduces the iron oxide to iron.
2
o
The chemical reaction for iron turning into rust is:
2Fe + 2H O+ O 2Fe + 4OH
2
2
2
-
Fe + 2OH Fe(OH)
2+
-
2
Fe(OH) =O => Fe(OH)
2
2
3
Fe(OH) =dehydrates=> Fe O .nH O or rust
3
2
3
2
Students should attempt to design a formula that produces Fe O by reacting with oxygen and
water.
2
3
The temperature required to produce aluminium from bauxite in a normal furnace is far too
high to be practical. To produce aluminium from bauxite there are two major steps. The
chemical formula for bauxite is (AlO (OH) ). The first part of the process removes all the
impurities that are mined with the bauxite and produces alumina (Al O ). Sodium hydroxide
(NaOH), heat and pressure are required to go through a number of chemical reactions to
separate the mixture of chemicals into pure Al O . This looks like a white powder. At the end of
the process the sodium hydroxide (NaOH) can be reused after some of the impurities are
removed.
x
3–2x
2
2
3
3
The following equation shows this (leaving out the middle steps):
AlO (OH)
x
3–2x
+ 2 NaOH = Al O + 2 NaOH + water (H O)
2
3
2
Electricity is used to turn the alumina (Al O ) into aluminium (Al). First the alumina (Al O ) is
dissolved inside a reduction cell. Electricity is passed through the solution. The reduction cells
operate at about 900 C.
2
3
2
3
o
At the cathode the aluminium ions combine with electrons to produce molten aluminium.
Al + 3 e → Al
3+
−
At the anode oxygen is formed when each atom gives off two electrons.
2 O → O2 + 4 e
2−
−
Oil and Gas
In a process that takes in the order of 100 million years liquid and gas hydrocarbons
accumulate in pockets inside the Earth’s crust. They are mixed in with the surrounding
minerals, but can’t escape upwards as there is a cap of rock they can’t get through. We give
these hydrocarbons a general name called oil and gas.
This oil and gas is extracted by drilling oil wells. These hydrocarbons from oil wells can have
very different combinations of hydrocarbon compounds. The simplest hydrocarbon is
methane. Its chemical formula is CH . This is a gas and is commercially called natural gas. It is
the gas we use for cooking and heating. Some of the other hydrocarbons such as propane
are a gas when released into the atmosphere. The other hydrocarbons are liquid. The oil from
oil wells is refined in a refinery. The refinery produces hydrocarbons for specific needs such as
petrol, kerosene, diesel and engine oil. Oil wells that have very large hydrocarbons will be
used to make the tar that seals roads. The refining process produces hydrocarbons such as
ethylene that can be used to make plastics.
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Plastic
80 million tonnes of polyethylene is made worldwide every year. Polyethylene is made from
the hydrocarbon ethylene, which is a gas under normal conditions. The chemical formula for
ethylene is C H Ethylene is usually produced by the petrochemical industry, but can also be
made from ethanol.
2
4.
Polyethylene is a long chain made from ethylene molecules. The formula for most types of
polyethylene is (C H ) H A catalyst is used to produce the chemical reaction. During the
chemical reaction a lot of heat is produced. There are many types of polyethylene. The
length of the molecule and the way the chains are organised, tangled or cross bonded
produces plastics with different properties.
2
4 n
2.