Properties, uses and alloys
Metals are usually shiny, dense, malleable, ductile, good conductors of heat and electricity, and have high melting points. Many react with oxygen, water and dilute acids. An alloy is a mixture of a metal with other elements. The different-sized atoms disrupt the regular layers, so they can't slide easily: alloys are harder and stronger than pure metals. Examples: steel (iron + carbon), stainless steel (+ chromium, nickel), brass (copper + zinc).
≈ 30 minReactivity series
The reactivity series lists metals from most to least reactive: K, Na, Ca, Mg, Al, (C), Zn, Fe, (H), Cu, Ag, Au. More reactive metals form positive ions more easily. Metals above hydrogen react with dilute acids; metals above magnesium react with cold water. A more reactive metal displaces a less reactive one from a solution of its compound, e.g. .
≈ 35 minCorrosion of metals
Rusting is the corrosion of iron and steel. It needs both oxygen and water, and forms hydrated iron(III) oxide. Salt speeds it up. Barrier methods (paint, oil, grease, plastic, tin plating) keep oxygen and water away. Galvanising coats iron with zinc; zinc is more reactive, so even if scratched it corrodes first (sacrificial protection).
≈ 30 minExtraction of metals
Most metals are found as compounds in ores. Metals below carbon are extracted by reduction with carbon (heating with coke). Metals above carbon must be extracted by electrolysis of the molten compound, which costs more energy. Iron is made in the blast furnace from haematite (), coke and limestone. Aluminium is made by electrolysing aluminium oxide dissolved in molten cryolite.
≈ 45 min