Everything from the 8 lessons of this topic on a few pages: the key idea of each lesson, the diagram to remember, the points to learn and the traps examiners set. Read it, cover it, test yourself.
Metals are good conductors of heat and electricity, malleable (can be hammered into shape) and ductile (can be drawn into wires), and usually have high melting and boiling points. Non-metals are generally poor conductors and brittle when solid. Metals react with dilute acids to give a salt and hydrogen, with cold water or steam to give a hydroxide or oxide and hydrogen, and with oxygen to give metal oxides.
With cold water a reactive metal forms a hydroxide; with steam a metal forms an oxide. Magnesium reacts only very slowly with cold water but burns in steam to give magnesium oxide.
Choose a metal by matching its properties to the job. Aluminium is used in aircraft (low density, and strong as an alloy), overhead power cables (low density and a good electrical conductor) and food containers (resistant to corrosion). Copper is used in electrical wiring because it is a good conductor of electricity and is ductile.
Aluminium resists corrosion not because it is unreactive (it is high in the reactivity series) but because of a thin, tough layer of aluminium oxide that seals the surface. Say "resists corrosion", not "is unreactive".
An alloy is a mixture of a metal with other elements. Examples: brass is copper and zinc; stainless steel is iron with other elements such as chromium, nickel and carbon. Alloys can be harder and stronger than the pure metals and are used for that reason: stainless steel for cutlery because it is hard and resists rusting. Extended: in an alloy, atoms of different sizes disrupt the regular layers, so the layers cannot slide over each other as easily.
An alloy is a mixture, not a compound: the elements are not chemically combined and there is no fixed formula. And the added element need not be a metal: steel contains carbon, a non-metal.
The reactivity series, from most to least reactive, is: potassium, sodium, calcium, magnesium, aluminium, (carbon), zinc, iron, (hydrogen), copper, silver, gold. It is worked out from reactions with cold water, steam and dilute acids. A more reactive metal displaces a less reactive metal from a solution of its salt. Extended: the more reactive the metal, the more easily it loses electrons to form positive ions. Aluminium appears unreactive because of its protective oxide layer.
Aluminium is high in the series but often seems unreactive, for example it does not react with water. That is because its surface is sealed by a layer of aluminium oxide, not because it is low in the series. Remove the layer and it reacts vigorously.
Iron and steel rust only when both water and oxygen are present; rust is hydrated iron(III) oxide. Barrier methods (painting, greasing, coating with plastic) stop rusting by keeping out water and oxygen. Galvanising coats iron with zinc. Extended: zinc, or a block of magnesium, gives sacrificial protection: being more reactive, it loses electrons and corrodes instead of the iron, even if the surface is scratched.
A barrier only works while it is unbroken: once paint is scratched, iron underneath rusts. Galvanising protects even when scratched because zinc is more reactive than iron and corrodes in its place. Tin-plating does the opposite: tin is less reactive, so a scratched tin can rusts faster.
An ore is a rock that contains enough of a metal compound to make extraction worthwhile. The method of extraction depends on the metal's position in the reactivity series: metals below carbon (such as zinc, iron and copper) can be extracted by reduction of their oxides with carbon or carbon monoxide; metals above carbon (such as aluminium and sodium) must be extracted by electrolysis of a molten compound. Very unreactive metals such as gold are found uncombined.
Aluminium is not extracted with carbon, because aluminium is above carbon in the reactivity series. And the metal is reduced during extraction: whether by carbon or at the cathode, the metal ion gains electrons or the oxide loses oxygen.
The raw materials are hematite (iron ore, Fe2O3), coke (carbon), limestone (CaCO3) and hot air. Coke burns: C + O2 → CO2, giving heat. Carbon dioxide reacts with more coke: CO2 + C → 2CO. Carbon monoxide reduces the ore: Fe2O3 + 3CO → 2Fe + 3CO2. Limestone decomposes, CaCO3 → CaO + CO2, and the calcium oxide removes sand: CaO + SiO2 → CaSiO3 (slag).
The main reducing agent is carbon monoxide, not carbon: it is a gas that reaches every part of the ore. And limestone does not reduce anything; its job is to remove the sandy impurities as slag.
The ore is bauxite, purified to aluminium oxide, Al2O3. It is dissolved in molten cryolite, which lowers the operating temperature and improves conductivity, and electrolysed with carbon (graphite) electrodes. Aluminium forms at the cathode and oxygen at the anode. The oxygen reacts with the hot carbon anodes to form carbon dioxide, so the anodes must be replaced regularly. Extended: Al3+ + 3e− → Al and 2O2− → O2 + 4e−.
Cryolite is not a catalyst and not the source of aluminium: it is a solvent that lowers the temperature needed, saving energy. And it is the anodes, not the cathode, that must be replaced, because oxygen forms there and burns the carbon.