Topic 3 Metals and their uses

Extracting metals Metals are found in the Earth’s crust They are often chemically combined with other elements – this is called the ore Whether it is worth extracting a metal depends on: 1. How easy it is to extract it from its ore 2. How much metal the ore contains

Transition metals

Extracting metals The way we extract a metal depends on its place in the reactivity series Most reactive Least reactive Potassium Sodium Calcium Magnesium Aluminium Carbon Zinc Iron Tin Lead Copper Silver Gold Platinum electrolysis carbon reduction Other methods

Carbon reduction A more reactive metal will displace a less reactive metal from its compounds Many metals combine with oxygen – carbon will also displace less reactive metals from their oxides when heated with them Metal oxide + carbon  metal + carbon dioxide Lead oxide + carbon  lead + carbon dioxide 2PbO + C  2Pb + CO 2

Iron Iron ore contains iron combined with oxygen Iron is extracted using carbon reduction It is heated in a blast furnace Iron (III) oxide + carbon  iron + carbon dioxide Iron straight from the blast furnace still contains some impurities (it is about 96% iron) – it is very brittle and is called cast iron. It can be used to mould different shapes Removing the impurities gives us pure iron – this is too soft for most uses

Iron To make iron useful we can add small amounts of other elements A metal that is made by mixing in other elements (carbon or another metal) is called an alloy Steel is an alloy of iron Carbon steel contains between 0.03% and 1.5% carbon Low carbon steels are easily shaped High carbon steels are very strong and hard Iron with chromium and nickel makes stainless steel

Aluminium Aluminium is a very low density metal It can be alloyed with other elements to make it very strong It cannot be extracted from its ore by carbon reduction because it is more reactive than carbon It is extracted using electrolysis instead – an electric current is passed through molten aluminium oxide at high temperatures to break it down Electrolysis is very expensive because lots of energy is needed – this is why we recycle aluminium

Titanium Titanium is very strong, has a very high melting point and is resistant to corrosion It is used for jet engine parts, replacement hip joints and as nuclear reactor parts It cannot be reduced using carbon because it is more reactive than carbon It is reduced using sodium or magnesium, but this process has lots of steps, uses electrolysis to get the sodium or magnesium which means the titanium is very expensive

Copper Pure copper is a good conductor of electricity, does not react with water and can be shaped easily Copper can be removed from its ore by smelting This involved heating it in a furnace: Copper (I) sulfide + oxygen  copper + sulphur dioxide It can also be made by reduction with carbon Copper oxide + carbon  copper + carbon dioxide

Copper The copper produced is purified using electrolysis This involves passing an electrical current through a copper solution

Copper Copper-rich ores are running out There are always environmental problems associated with mining. New methods are used to extract copper from low grade ores Phytomining – using plants to extract copper Bioleaching – using bacteria to extract copper 20% of our copper comes from bioleaching Advantages? Disadvantages?

More alloys Bronze = copper + tin this is tough with resistant to corrosion (used to make statues) Brass = copper + zinc this increases the strength of copper but is still malleable (used to make musical instruments) Gold can be alloyed to increase its strength There are over 300 aluminium alloys with different properties