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Reactivity of metals (alloys (most everyday metals are alloys, bronze is…
Reactivity of metals
alloys
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bronze is an alloy of tin and brass, brass is an alloy of copper and zinc
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gold used in jewellery is usually an alloy of silver, copper and zinc and the proportion of gold in the alloy is measured in carats with pure gold being 24 carats
steels are alloys of iron that contains specific amounts of carbon and other metals, high carbon steel is strong but brittle whereas low carbon steel is softer and more easily shaped
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low grade metal ores
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copper ores are becoming scarce and new ways of extracting copper from low grade ores include phytomining and bioleaching
these methods avoid traditional methods such as digging, moving and disposing of large amounts of rock
phytomining - uses plants to absorb metal compounds, the plants are harvested and then burned to produce the ash that contains metal compounds
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corrosion and rusting
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rusting is an example of corrosion, both air and water are necessary for iron to rust
corrosion can be prevented by applying a coating that acts as a barrier such as greasing, painting or electroplating
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extraction of metals
unreactive metals such as gold are found in the earth as the metal itself but most metals are found as compounds that need chemical reaction to extract the metal
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metals react with oxygen to produce metal oxides, the reaction is oxidation because the metals gain oxygen