In GCSE Science students will look at some of the materials used in building, such as limestone or metals. This is the third of seven quizzes on that topic - and the second of two on extracting metals from the ground - and it looks in particular at extracting reactive metals.
The rocks of the Earth's crust contain metals in the form of metal compounds like iron oxide and aluminium oxide. These are often mixed with other substances and where they occur in a high enough concentration, we call them ores. An ore is a rock from which a metal can be extracted economically.
Ores are mined from the ground on a large scale. They often need to be concentrated even more before the metal is extracted and purified. The economics of using a particular ore may change over time. For example, as a metal becomes rarer, an ore that only has a low concentration of the metal may be used when it was previously considered too expensive to mine.
Many ores are the oxides of a metal and when metal oxides are reduced (have their oxygen removed), the metal is left. How this is done depends on the reactivity of the metal. The extraction of reactive metals like aluminium is usually carried out by using electrolysis. That is relatively easy nowadays, there is plenty of electricity available and so aluminium is a commonly used metal.
But this wasn't always the case. Aluminium ore is extremely difficult to melt and before the 'easy' method of melting it had been discovered, the only way of producing aluminium was to displace it from its compounds using an even more reactive metal. So only very rich people could afford things made from aluminium - in fact one of the ways that they showed off their wealth in the middle of the nineteenth century was to provide dinner guests with cutlery made from aluminium instead of silver!
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