CC11 Using And Obtaining Metals

• A reactivity series shows elements arranged in order of their reactivity with water and acid, with the most reactive at the top.
• The more bubbles of gas seen / formed, the more reactive the metal.
• The rate of reaction is greater in warm water/acid than in cold water/acid.
• A more reactive metal will DISPLACE a less reactive metal from a salt. 
• Observations in displacement reactions may include: an increase in temp, loss of colour of the reactant salt solution or the formation of a solid product.
• An ore is a rock containing enough of a compound to extract a metal for profit.
• Two methods of extraction:

  • Heating with carbon – for metals less reactive than carbon.

  e.g. iron is extracted by heating iron oxide with carbon. Carbon is more reactive and so displaces the iron:

  iron oxide  +  carbon  🡪  iron  +  carbon dioxide

  • Electrolysis – for metals more reactive than carbon.

  e.g. aluminium is produced by the electrolysis of aluminium oxide:

  aluminium oxide  🡪  aluminium  + oxygen
• The more reactive a metal is, the harder it is to extract. 

  The harder a metal is to extract, the more it costs to extract.
• The extraction of metals involves the reduction of ores. 
• The advantages of recycling metals =

  1. Natural reserves of metal ores will last longer.
  2. The need to mine ores is reduced. Mining can damage the landscape as well as create noise and dust pollution.
  3. Many metals need less energy to recycle them than to extract new metal from the ore.
  4. Scrap metal would be being disposed of, so recycling means that less waste metal ends up in landfill.
• The disadvantages of recycling metals = Costs and the energy used in collecting, transporting and sorting metals to be recycled.
• Phytoextraction – growing plants to absorb metal compounds in soil. The plants are burned to form an ash that you can extract the metal from.
• Bioleaching – growing bacteria on an ore that has very little metal in it. The bacteria produce a solution containing copper ions, called a leachate. Copper is extracted from the leachate by displacement using scrap iron, then purified by electrolysis. 
• advantages of bioleaching = no harmful gases produced, causes less damage to landscape than mining, conserves supplies for higher grade ores, does not require the use of high temperatures and energy
• disadvantages of bioleaching = toxic substances can be produced and damage the environment
• advantages of phytoextraction = no harmful gases produced, causes less damage than mining, conserves supplies of higher grade ores, can be used to extract metals from contaminated ores which decontaminates the soil
• disadvantages of phytoextraction = more expensive than mining some ores, growing plants is dependant on weather
• A life cycle assessment is carried out to work out the environmental impact of a product. It can be used to compare the effect of using different materials for the same product.