 Metal Ores Noadswood Science, 2011

Metal Ores  To know how metal ores are reduced Saturday, October 01, 2016

Rocks, Minerals & Ores  What is the difference between a rock, mineral and ore?  A rock is a mixture of minerals  A mineral is any solid element or compound formed naturally within the Earth’s crust  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  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)  Extraction usually involves chemical reduction using carbon or via electrolysis  * Some metals are found as a metal, not an ore, such as gold (although it is very rare)

Reactivity Series  Can you remember the reactivity series – write a mnemonic for the reactivity series to help you remember it… Potassium Sodium Calcium Magnesium Aluminium (Carbon) Zinc Iron Lead (Hydrogen) Copper Silver Gold Platinum

Practical  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)  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)  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  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  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  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  The carbon and the oxygen form carbon dioxide, leaving the metal (as an element) behind  This occurs within the blast furnace…

Iron Extraction  Iron is extracted from iron ore in a huge container called a blast furnace (iron ores such as haematite contain iron oxide)  The oxygen must be removed from the iron oxide to leave the iron behind (reduction reaction)  Carbon is more reactive than iron, displacing the iron Iron oxide + Carbon  Iron + Carbon dioxide 2Fe 2 O 3 + 3C  4Fe + 3CO 2

Iron Extraction  In this reaction, the iron oxide is reduced to iron, and the carbon is oxidised to carbon dioxide  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 Fe 2 O 3 + 3CO  2Fe + 3CO 2

Blast Furnace

Raw Materials Raw materialContainsFunction Iron ore (haematite) Iron oxideA compound that contains iron CokeCarbon Burns in the air producing heat, and reacts forming CO (reducing the iron oxide) LimestoneCalcium carbonate Helps to remove acidic impurities from the iron by reacting with them forming molten slag AirOxygen Allows the coke to burn, producing heat and CO

Impurities  During the iron producing the main impurity is sand (silicon dioxide) which is still solid at 1500 o C  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: - CaCO 3  CaO + CO 2 CaO + SiO 2  CaSiO 3 (molten slag)