Metal Ores

1. Metal Ores Noadswood Science, 2011

2. Metal Ores • To know how metal ores are reduced

3. 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)!

4. 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)

5. 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

6. 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!!!

7. Practical • Ensure your desk is tidy, with nothing around it (or the floor) • Set up 2x heat-proof mats + tripod + gauze • Choose either iron, lead or copper oxide, and place a few grams within the crucible • Add an equal amount of carbon into the crucible • Heat for at least 10 minutes – be extremely careful • Only lift the crucible when it is cool using the tongs!

8. 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

9. 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…

10. 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 2Fe2O3 + 3C  4Fe + 3CO2

11. 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 Fe2O3 + 3CO  2Fe + 3CO2

12. Blast Furnace

13. Raw Materials

14. Impurities • During the iron producing the main impurity is sand (silicon dioxide) which is still solid at 1500oC • 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)