Metals and their extraction

• Metal extraction

  Metals are extracted from ores which are rocks containing metal compounds found in the Earth's crust. These metals can be extracted using chemical reactions.
• Metal reactivity

  The more reactive a metal is, the more stable its metal compound so the harder it is to extract the pure metal
• Extraction processes depending on metal reactivity

  • Electrolysis - for metals more reactive than carbon
  • Reduction with carbon - for metals less reactive than carbon
  • Metals less reactive than hydrogen are found pure in their native form
• Displacement reaction

  When a more reactive metal displaces a less reactive metal from a compound. Can be used to investigate the relative reactivities of metals.
• Oxidation

  Gain of oxygen, loss of electrons, loss of hydrogen. The species oxidised is known as the reducing agent.
• Reduction

  Loss of oxygen, gain of electrons, gain of hydrogen. The species reduced is known as the oxidising agent.
• Extraction of iron in a blast furnace

  1. Coke reacts with oxygen in the air to form carbon dioxide (exothermic combustion reaction)

  2. The carbon dioxide reacts with more coke to form carbon monoxide (the carbon dioxide is reduced)

  3. The iron oxide reacts with the coke or carbon monoxide and is reduced to form molten iron
• Removing impurities from iron ore in a blast furnace

  1. Limestone undergoes thermal decomposition into calcium oxide

  2. The calcium oxide reacts with the silicon dioxide to form solid calcium silicate which can be removed from the furnace (neutralisation reaction)
• Electrolysis

  When a metallic compound is melted or dissolved, the ions are free to move within the liquid or solution. Passing a current through molten liquids or solutions means that the solution can be broken down into elements.
• Electrolysis of molten lead bromide

  1. Pb2+ ions move to the cathode and lead is produced

  2. Br- ions move to the anode where two bromide ions lose an electron each to form liquid bromine
• Industrial extraction of aluminium using electrolysis

  1. Aluminium oxide is melted so electricity can be passed through it

  2. Aluminium oxide is dissolved in cryolite which lowers the melting point

  3. Aluminium metal forms at the negative electrode and sinks to the bottom of the tank

  4. Oxygen forms at the positive electrode and reacts with the carbon in the graphite electrodes forming CO2
• Iron

  • Malleable
  • Can form steel alloy with carbon which is harder and stronger than iron and less likely to rust
  • Used to build cars and in the construction industry
• Aluminium

  • Low density
  • Light weight for its size
  • Resists corrosion due to the very thin layer of their oxides on the surface
  • Used in aircraft, trains, overhead power cables, saucepans and cooking foil
• Copper


  • Good conductor of electricity and heat
  • Soft, easily bent and shaped (malleable)
  • Resistant to corrosion (very unreactive)
  • Used in electrical wiring, gas and water pipes, and plumbing in houses as copper doesn't react with water
• Titanium

  • Low density
  • Light weight for its size
  • Resists corrosion
• Aluminium

  • Low density
  • Light weight for its size
  • Resists corrosion due to the very thin layer of their oxides on the surface
• Uses of copper

  • Electrical wiring
  • Gas and water pipes
  • Plumbing in houses as copper doesn't react with water
• Uses of titanium


  • Fighter aircraft
  • Artificial hip joints
  • Pipes in nuclear power stations
• General properties of transition metals

  • High melting points
  • Form coloured compounds
  • Have the ability to form ions with different charges
  • Most are malleable and ductile
  • Good conductors of both heat and electricity due to their delocalised electrons
  • Hard
  • Less reactive than alkali metals (group 1 metals)
• Test for metal ions

  When sodium hydroxide (NaOH) is added:

  Copper (II) ions give a blue precipitate

  Iron (II) ions give a green precipitate

  Iron (III) ions give a brown precipitate
• Alloy


  A substance made of a mixture of 2 or more elements, of which at least one is a metal

  They are made by mixing molten metals

  The composition of alloys can be changed to produce alloys with desired properties
• Electrolysis of water

  Positively charged hydrogen ions move to the negative electrode and gain electrons in a reduction reaction

  Negatively charged hydroxide ions move to the positive electrode and lose electrons to form water and oxygen in an oxidation reaction
• Half equations in the electrolysis of water

  At the cathode: 4H+(aq) + 4e− → 2H2(g)

  At the anode: 4OH−(aq) → O2(g) + 2H2O(l) + 4e−
• Electrolysis of aqueous solutions

  At the cathode, hydrogen is produced unless the positively charged ions in the ionic compound are from a metal less reactive than hydrogen - then this metal will be produced instead

  At the anode, oxygen will be produced unless the ionic compound contains halide ions (Cl-, Br-, I-), in this case the halogen will be produced
• Electrode equations in the electrolysis of copper(II) chloride

  At the cathode: Cu2+(aq) + 2e– → Cu(s)

  At the anode: 2Cl–(aq) → Cl2(g) + 2e–
• Electrode equations in the electrolysis of sodium chloride

  At the cathode: 2H+(aq) + 2e- → H2(g)

  At the anode: 2Cl-(aq) → Cl2(g) + 2e-
• Uses of electrolysis


  • Electroplating

  Purification of copper

  Manufacture of sodium hydroxide, hydrogen gas and chlorine gas
• Factors to consider when extracting metals

  • Site of extraction plants: Good infrastructure, close to power station, near a city as a source for workers, away from built-up areas due to noise and pollution

  The method used - reduction with carbon to be used where possible to lower energy and costs needed

  Recycling - using recycling plants to recycle and reuse materials as opposed to extract new raw materials