The first series in use: iron to zinc
Iron is the metal of heavy industry: reinforced concrete, electricity pylons, rails and tools are made of it, and iron is also the catalyst in making ammonia. Cobalt can be magnetised like iron, so it is used in strong magnets and in rechargeable cells; its form cobalt-60 gives gamma rays used to inspect welds, a job for trained people only. Nickel gives hard steels that resist rust, rechargeable cells, a nickel–chromium alloy for heating coils (it resists corrosion when hot), shiny plating and, as a fine powder, a catalyst that hardens oils. Copper was one of the first metals people worked; with tin it makes bronze, and it carries electricity well, so it fills cables and coins. Copper(II) sulphate is used against fungi on crops. Fehling’s solution, a blue copper compound, turns orange-red with some sugars such as glucose: a laboratory test, not for home. Zinc coats iron (galvanising) to protect it, ZnO goes into paints, rubber and cosmetics, and ZnS is used in luminous paints and screens.
| Element | Property that matters | Use |
|---|---|---|
| iron | strong, cheap, magnetic | concrete reinforcement, pylons, rails, catalyst for ammonia |
| cobalt | can be magnetised | magnets, rechargeable cells |
| nickel | resists rust and acids | hard steels, heating coils, plating, catalyst for oils |
| copper | conducts electricity well | cables, coins, bronze |
| zinc | protects iron | galvanising, ZnO in paints, ZnS in luminous paints |
| Alloy | Made from | Property used |
|---|---|---|
| bronze | copper + tin | hard, easy to cast |
| heating coil alloy | nickel + chromium | resists corrosion when hot |
| steel | iron + carbon | strong and hard |
A magnet test, with a grown-up. Hold a fridge magnet near an iron nail, a steel fork, a ball of aluminium foil and a coin, and make a table of object and attracted: yes or no. Iron and steel are clearly attracted. Some coins have a steel core, so if yours is attracted you have learned something about that coin. Then compare a steel nail and a copper-coloured coin by shine, colour and how heavy each feels. Optional extra: put a copper-coloured coin in a cup of cold vinegar with a pinch of salt and see what happens after some minutes. Do not taste anything, wash your hands afterwards and pour the liquid away with water.