Rock that contains enough of a metal or a metal compound to make it worth extracting the metal is known as an ore. Mining ores often involves digging up large amounts of rock. The ore may need to be concentrated before the metal is extracted. These processes produce large amounts of waste and have major impacts on the environment.
A few unreactive metals that are low in the reactivity series (eg gold) are found in the Earth as the metal. Gold can be separated from rocks by physical methods. However, most metals are found as compounds, so the metals have to be extracted by chemical reactions. Metals can be extracted from compounds by displacement using a more reactive element. Metals which are less reactive than carbon can be extracted from their oxides by heating with carbon. A reduction reaction takes place as carbon removes the oxygen from the oxide to produce the metal.
IRON AND STEELS
Many of the ores used to produce iron contain iron(iii) oxide. Iron(iii) oxide is reduced at high temperatures in a blast furnace using carbon. The iron produced contains about 96% carbon. The impuritites make it hard and brittle, so it only has a few uses as cast iron. Removing all the carbon and other impurities makes pure iron, but this is too soft for many uses.
Most iron is used to make steels. Steels are alloys of iron because they are mixtures of iron with carbon and other elements. Alloys can be made so that they have properties for specific uses. The amounts of carbon and other elements are carefully adjusted when making steels. Low-carbon steels are easily shaped and high-carbon steels are hard. Some steels, such as stainless steels, contain larger quanitities of other metals. They are made this way so that they resist corrosion.
ALUMINIUM AND TITANIUM
Aluminium has a low density and although it is quite high in the reactivity series, it is resistant to…