After iron and aluminium, copper is probably the third most important industrial metal. It is used in electrical wiring and for printed circuit boards (PCB). The board is completely coated in copper then copper is etched away to leave the path that the electricity needs to follow. Copper is also used for plumbing although it is increasingly being replaced by PVC pipe which is cheaper but just as flexible and strong. Copper is also used to make two important alloys, bronze and brass.
Bronze is a mixture of copper and tin and is used to make bells, cymbals and other musical instruments. It is also used to makes ships’ propellers and by sculptors for statues. Brass is a mixture of copper and zinc and is also used to make musical instruments; decorative features such as door handles and light fittings; applications where corrosion resistance is particularly important such as ship building; and many countries use brass for coinage. Copper is a relatively expensive metal with a current price of $9,208 per tonne.
Physical properties
Copper is highly ductile and an excellent conductor of electricity and heat. It is a relatively soft metal, which partly explains why it is such a good conductor. It is one of only four non-grey/silver metals (the other being caesium & gold – which are yellow and osmium – which is blue). Pure copper is an orange/red colour and it turns darker on exposure to air as it oxidises. Copper melts at 1080 °C and has a high density of 8.4 g/cm³.
Chemical properties
Copper is not a very reactive metal. It is lower in reactivity than hydrogen so it does not react with most acids (nitric acid being a notable exception – gold, which is often found with copper, is purified by washing with nitric acid which dissolves the copper but leaves the gold untouched.) Copper produces coloured compounds; copper oxide is black; copper sulfate is blue (as are many of its other salts); copper carbonate is green. The Statue of Liberty is made from copper and appears green because of the coating of copper carbonate (verdigris) on its surface. Copper oxide formed by exposure to the air then reacts with carbon dioxide dissolved in rain water to produce copper carbonate.
Extraction
Copper is sufficiently unreactive that it can be found as native copper and it has been in use by mankind for at least 10,000 years. The earliest ore was malachite, a greenish mineral containing copper carbonate. Most copper is now mined as ores containing copper sulfide which is a dark blue colour. These can be reduced to liquid metal by smelting in a blast furnace. Copper is often needed in very high purities and so electrolysis is used to produce 99.99% pure copper for the electronics industry. This is a cold process unlike the hot electrolysis of cryolite used to extract aluminium from its ore.
This is a good video but it has long periods of silence between the commentary which makes it a little eerie. What she has to say is worth hearing, though, so try to stick it out for its entire 4.43 minutes.
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Questions…
- What would be the products of a reaction between copper oxide and sulfuric acid?
- Suggest a physical property shared by all metals.
- What substance is formed when copper reacts with sulphur?
- Name an alloy other than brass or bronze, and list its components.
- Of what type of reaction is the formation of verdigris an example?
- When copper chloride solution is poured into an aluminium foil cup, it eats its way through the aluminium. What type of reaction is this?
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