CC11- obtaining and using metals

• potassium has more outer shells than sodium so the outer electron is further from the nucleus, reducing the attraction and therefore making it easier to lose the electron.

  group one metals lose 1 electron when they react and group 2 lose 2, so group one is more reactive as it‘s easier to lose one electron.
• potassium, sodium, lithium and calcium will react with water to form a metal hydroxide and hydrogen gas.

  magnesium, aluminium, zinc and iron react slowly with water, but react with steam to form a metal oxide and hydrogen gas.

  copper, silver and gold do not react with water.
• when metals react with acids they form salts and hydrogen gas.

  copper, silver and gold do not react with acids.

  potassium and sodium react violently so it is unsafe.
• metals can be reacted with salt solutions, if the metal on its own is more reactive than the metal in the salt, they will switch places- this is a displacement reaction.
• displacement reactions are also redox reactions.

  in a redox reaction, oxidation and reduction occur.
• extraction is the process of obtaining the pure metal from a compound, eg iron from iron oxide.

  an ore is a rock that has enough of the metal that it can be extracted for profit.
• all metals more reactive than carbon are extracted using electrolysis.

  all metals less reactive than carbon are extracted using carbon, which displaces these metals from their compounds.

  un reactive metals are found as pure metals so there is no need for extraction.
• phytoextraction:

  1. plants are grown on low grade ores
  2. plants absorb metal ions through their roots
  3. ions become concentrated and plants are burned.
  4. metal is harvested from the ash
  5. slow, but makes use of low grade ores and reduces need to mine.
• bioleaching:

  1. bacteria break down ores to form solutions containing metal ions
  2. solution is called leachate
  3. metals obtained from solution by displacement reactions- eg scrap ion displaces cooper from leachate to obtain pure copper.
  4. bioleaching produces harmful substances such as sulphuric acid which can harm the environment.
• both bioleaching and phytoextraction are slow, but no harmful gases are produced, they cause less damage to the landscape compared to mining and conserve supplies of higher grade ores.
• LCA, or life cycle assessments are used to work out the environmental impact of a product, decide whether it is worthwhile to manufacture and recycle a product, and compare the effect of using different materials for the same product.

  some questions asked are:

  • what raw materials are needed and how are they processed?
  • how much energy is required and where will it come from?
  • what will the product be used for and how will it be disposed?
• advantages of recycling include:

  1. natural reserves of metal ores will last longer
  2. mining will be reduced, which damages landscape
  3. less pollution such as sulfur dioxide will be produced
  4. less energy is used to recycle compared to extraction.
  5. less waste material ends up in landfill sites.

  disadvantages include:

  1. the cost and expense involved in collecting, transporting, and sorting metals