GCSE Combined Science (AQA)

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Extraction of Aluminium

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Chemical changes Electrolysis

Extraction of Aluminium

5:15 Electrolysis of Ionic Compounds and Metal Extraction
Spec 4.4.3.3
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  • Aluminum is a metal with many applications such as cans, foils, roofing, and car bodies.
  • It is the second most used metal after iron and the most abundant metal on earth.
  • Aluminum is found in ores and rocks, commonly in bauxite as aluminum oxide (Al2O3).
  • Aluminum must be extracted using electrolysis, a process that separates ions in an ionic compound.
  • Aluminum is manufactured by the electrolysis of a molten mixture of aluminum oxide and cryolite.
  • Electrodes in the process are made with carbon instead of metal.
  • The container itself is used as the cathode in the setup.
  • Cryolite is used as a molten solvent to dissolve aluminum oxide, allowing ions to move freely.
  • Cryolite has a lower melting point than aluminum oxide, saving energy and reducing costs.
  • The melting point of aluminum oxide is over 2000 degrees, but with cryolite, it drops to under 1000 degrees.
  • Aluminum ions are attracted to the cathode, gain electrons, and form aluminum metal.
  • The process is kept at a high temperature, so aluminum is in a molten state and sinks to the bottom.
  • Liquid aluminum is collected from the bottom of the container.
  • Oxide ions are attracted to the anodes, lose electrons, and form oxygen molecules.
  • Oxygen reacts with the carbon anode to form carbon dioxide, causing the anode to burn away.
  • The anode needs to be continually replaced to maintain a complete circuit for electrolysis.

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