metals

• The Earth's crust contains metals and metal compounds such as gold, iron oxide and aluminium oxide, but when found in the Earth these are often mixed with other substances.
• To be useful, the metals have to be extracted from whatever they are mixed with.
• A metal ore is a rock containing a metal (in elemental form or as a compound) in a high enough concentration to make it worthwhile extracting the metal
• The most common metal ores are oxides and sulfides. Sulfides are the oldest ores, formed in the Earth's history when there was a lot of sulfur from volcanic activity.
• Oxides formed later when photosynthesis in plants released large amounts of oxygen into the atmosphere.
• Metal ore deposits are a finite resource (there are only a certain amount of them) and non-renewable (once used, they are gone and will not be replaced).
• Many metals are obtained today from recycling (smelting and refining) scrap metals. About half of the aluminium, copper, lead, steel and tin that is used in the UK come from recycled scrap metal.
• You need to be able to identify the metals present in given ores from their chemical formulae.
• Metal: Aluminium

  Metal ore: Bauxite

  Chemical Formulae: Al2O3
• Metal: Chromium

  Metal Ore: Chromite

  Chemical Formulae: FeCr2O4
• Metal: Copper

  Metal Ore: Chalcocite

  Chemical Formulae: Cu2S
• Metal Ore: Malachite

  Chemical Formulae: Cu2CO3(OH)2
• Metal: Mercury

  Metal Ore: Cinnabar

  Chemical Formulae: HgS
• Metal: Titanium

  Metal Ore: Rutile

  Chemical Formulae: TiO2
• Metal: Iron

  Metal Ore: Hematite

  Chemical Formulae: Fe2O3
• The method used to extract metals from the ore depends on their reactivity
• potassium, sodium, calcium, magnesium and aluminium are the most reactive metals so they are extracted by electrolysis
• zinc, iron, tin and lead are extract by reduction with carbon or carbon monoxide
• copper, silver, gold and platinum are the least reactive and are found in their pure form or extracted by various chemical reactions
• Gold and platinum occur in the Earth as native metal. This means that they are found as the element, not the compound, and so do not need to be reduced.
• Reduction is the process of removing oxygen
• Oxidation is the process of gaining oxygen
• Electrolysis is the process of using electricity to extract a metal
• A metal will displace (take the place of) a less reactive metal in a metal salt solution.
• Example of displacement

  iron + copper(II) sulfate -> iron sulfate + copper
• If we look at the reactivity series, iron is more reactive than copper, as a result iron displaces copper.
• Reduction is the loss of oxygen from a compound
• Oxidation is the gain of oxygen to form a compound
• During these reactions, the more reactive metal “takes” the oxygen off the less reactive