Copper can be extracted from its ore by heating it with carbon. Impure copper is purified by electrolysis in which the anode is impure copper, the cathode is pure copper, and the electrolyte is copper sulphate solution.

An alloy is a mixture of two elements, one of which is a metal. Alloys often have more useful properties than the metals they contain.

Extraction and purification of copper

Copper is less reactive than carbon, so it can be extracted from its ores by heating it with carbon. For example, copper is formed if copper oxide is heated strongly with charcoal - which is mostly carbon:

copper oxide + carbon    →    copper + carbon dioxide

Copper is purified by electrolysis. Electricity is passed through solutions containing copper compounds, such as copper sulphate. The anode - positive electrode - is impure copper. Pure copper forms on the cathode - negative electrode.

An alloy is a mixture of two elements, one of which is a metal. Alloys often have properties that are different to the metals they contain. This makes them more useful than the pure metals alone. For example, alloys are often harder than the metal they contain.

Alloys contain atoms of different sizes, which distorts the regular arrangements of atoms. This makes it more difficult for the layers to slide over each other, so alloys are harder than the pure metal.

alloymain metal(s) in alloytypical use amalgam mercury dental fillings brass copper and zinc hinges, electrical plugs solder lead and tin

joining metals

Smart alloys have unusual properties. Nitinol is an alloy of nickel and titanium, and is known as a shape memory alloy. If nitinol is bent out of shape, it returns to its original shape when it is either heated or an electric current is passed through it. This property makes it useful for making spectacle frames - they return to their original shape if they are put in hot water after bending them.