Where do metals come from?
- Metals found in the earth's crust.
- Most metals are found chemically combined with other elements, usually oxygen, so the metal must be chemically seperated from its compound before use.
- In some places there is enough of a metal/metal compound in a rock to make it worth extracting the metal, then the rock is called a metal ore.
- Ores are mined from the ground and some need to be concentrated before extractng and purifying the metal.
- E.g. Copper ores are ground into powder then mixed with water and a chemical that makes the copper compound repel water. Then, air is bubbled through the mixture and copper compound floats on the top as a froth. The rocky bits sink and the concentrated copper compund is scrapped off the top. It is then ready to have its copper extracted.
- Whether it is worth extracting a metal depends on: how easy it is to be extracted from its ore and how much metal the ore contains.
- Gold and Silver are so unreactive that they are found in the earth as metals- native state.
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How do we extract metals?
- Method depends on the place of the metal in the reactivity series- a more reactive metal will displace a less reactive metal from its compunds.
- Carbon (non-metal) will displace less reactive metals from their oxides.
- Many metals such as Copper, Lead, Iron and Zinc are combined with oxygen (metal oxides). Carbon is more reactive than these metals so it can be used to extract them from their oxides.
- The metal oxide is heated with carbon. The carbon removes the oxygen from the metal oxide to form carbon dioxide.
- E.g. metal oxide + carbon → carbon dioxide.
Lead oxide + carbon → lead + carbon dioxide.
- The removal of oxygen from a compund is called chemical reduction.
- Metals more reactive than carbon are extracted via electrolysis.
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