Transcript Natural Selection

Metal Ores
S
Noadswood Science, 2011
Thursday, July 16, 2015
Metal Ores
S To know how metal ores are reduced
Rocks, Minerals & Ores
S What is the difference between a rock, mineral and ore?
S A rock is a mixture of minerals
S A mineral is any solid element or compound formed naturally
within the Earth’s crust
S A mineral ore is a mineral which contains enough metal to make
it worth while extracting the metal from (i.e. you’ll make enough
money after all the ‘trouble’ needed getting the metal out)!
Reactivity
S The more reactive a metal, the harder it is to extract – extracting
requires a chemical reaction to separate the metal (in many cases
the metal is found as an oxide)
S Extraction usually involves chemical reduction using carbon or via
electrolysis
S * Some metals are found as a metal, not an ore, such as gold
(although it is very rare)
Reactivity Series
S Can you remember the reactivity series – write a mnemonic for
the reactivity series to help you remember it…
Potassium
Sodium
Calcium
Magnesium
Aluminium
Zinc
Iron
Lead
Copper
Silver
Gold
Platinum
(Carbon)
(Hydrogen)
Practical
S The experiment you are going to perform today will be to purify iron
from iron oxide (we also have copper from copper oxide and lead from
lead oxide)
S It requires vigorous heating of the ore within a crucible (also containing
carbon) – this is a reduction reaction (the carbon removes the oxygen
from the metal oxide)
S You will be heating the crucible on full heat from the Bunsen for at least
ten minutes – be aware of what is around you as the apparatus will
become red hot!!!
Practical
1.
Ensure your desk is tidy, with nothing around it (or the floor)
2.
Set up 2x heat-proof mats + tripod + gauze
3.
Choose either iron, lead or copper oxide, and place a few grams within
the crucible
4.
Add an equal amount of carbon into the crucible
5.
Heat for at least 10 minutes – be extremely careful
6.
Only lift the crucible when it is cool using the tongs!
Metal Extraction
S The way in which a metal is extracted depends on its reactivity – a
more reactive metal will displace a less reactive metal from its
compounds
S Carbon (a non-metal) will also
displace less reactive metals
from their oxides – carbon is
used to extract metals from
their ores commercially
Metal oxide + Carbon  Metal + Carbon dioxide
Metal Extraction
S When a metal oxide is heated with carbon (e.g. iron oxide, copper
oxide, lead oxide etc…) the carbon removes the oxygen from the
metal oxide
S The carbon and the oxygen
form carbon dioxide, leaving
the metal (as an element)
behind
S This occurs within the blast
furnace…
Iron Extraction
S Iron is extracted from iron ore in a huge container called a blast
furnace (iron ores such as haematite contain iron oxide)
S The oxygen must be removed from the iron oxide to leave the iron
behind (reduction reaction)
S Carbon is more reactive than iron, displacing the iron
Iron oxide + Carbon  Iron + Carbon dioxide
2Fe2O3 + 3C  4Fe + 3CO2
Iron Extraction
S In this reaction, the iron oxide is reduced to iron, and the carbon
is oxidised to carbon dioxide
S In the blast furnace, it is so hot that carbon monoxide can be used
to reduce the iron oxide in place of carbon: Iron oxide + Carbon monoxide  Iron + Carbon dioxide
Fe2O3 + 3CO  2Fe + 3CO2
Blast Furnace
Raw Materials
Raw material
Contains
Function
Iron ore
(haematite)
Iron oxide
A compound that contains iron
Coke
Carbon
Burns in the air producing heat, and reacts
forming CO (reducing the iron oxide)
Limestone
Calcium carbonate
Helps to remove acidic impurities from the iron
by reacting with them forming molten slag
Air
Oxygen
Allows the coke to burn, producing heat and
CO
Impurities
S During the iron producing the main impurity is sand (silicon
dioxide) which is still solid at 1500oC
S The limestone is decomposed by the heat into calcium oxide and
carbon dioxide – the calcium oxide reacts with sand to form
calcium silicate (slag) which is molten and can be tapped off: CaCO3  CaO + CO2
CaO + SiO2  CaSiO3 (molten slag)