Carbon is a non-metal but it is more reactive than some metals. This means that some metals can be extracted from their metal oxides using carbon.
Less reactive metals than carbon can be extracted from their oxides by heating with carbon. In general:
metal oxide + carbon → metal + carbon dioxide
This works for zinc, iron, tin, lead and copper. Copper is the least reactive of these five metals.
To extract copper, you mix copper oxide powder with carbon powder. You then heat the mixture strongly for a few minutes in a crucible. It is important to keep a lid on the crucible, otherwise the carbon will react with oxygen in the air, rather than with the copper oxide. The carbon dioxide formed in the reaction escapes into the air.
After letting the crucible cool down, you tip the mixture into cold water. Pieces of brown copper sink to the bottom, leaving unreacted powder suspended in the water.
These equations represent the reaction:
copper oxide + carbon → copper + carbon dioxide
2CuO + C → 2Cu + CO2
Iron is less reactive than carbon, so it can be extracted from iron oxide using carbon. This is done on an industrial scale in a huge container called a blast furnace.
Lumps of iron oxide are mixed with carbon and dropped into the top of the blast furnace. Hot air is blasted in at the bottom. The oxygen in the air reacts with the carbon, forming carbon monoxide:
carbon + oxygen → carbon monoxide
2C +O2 → 2CO
It is hot enough in the blast furnace for the carbon monoxide to react with the iron oxide:
iron oxide + carbon monoxide → iron + carbon dioxide
Fe2O3 + 3CO → 2Fe + 3CO2