Ores

• What are very unreactive metals found in their native state?


  Gold and platinum
• Why do more reactive metals not exist in their native state?

  They have reacted with other elements to form compounds
• What is the process of obtaining a metal from its compounds called?


  Extraction
• What is an ore?

  A rock that contains enough of a compound to extract a metal for profit
• What is haematite an ore of?

  Iron oxide
• How is iron extracted from iron oxide?

  By heating it with carbon
• Why does carbon displace iron in the extraction process?

  Because carbon is more reactive than iron
• Write the chemical equation for the extraction of iron from iron oxide using carbon.

  iron oxide + carbon → iron + carbon dioxide
• What type of metals can be extracted using the method described for iron?

  Metals below carbon in the reactivity series
• What is malachite an ore of?

  Copper carbonate
• What happens to malachite when it is heated?

  It converts to copper oxide
• How is copper produced from copper oxide?

  By heating it with carbon
• What method is used to extract metals higher than carbon in the reactivity series?

  Electrolysis
• What does electrolysis involve?

  Passing electricity through a molten ionic compound
• What is produced from the electrolysis of aluminium oxide?

  Aluminium and oxygen
• What is the ore from which aluminium is extracted?

  Bauxite
• Why is electrolysis considered extremely expensive?

  Because a lot of energy is needed to keep metal oxides molten
• When is electrolysis used for metal extraction?

  For very reactive metals that cannot be obtained by heating their oxides with carbon
• What is the process used to extract aluminium from aluminium oxide?


  Electrolysis
• What is aluminium oxide commonly found in?

  Ore called bauxite
• What is the chemical reaction for the electrolysis of aluminium oxide?

  Aluminium oxide → Aluminium + Oxygen
• Where do metals come from?

  Metals come from the Earth's crust
• In what form are metals typically found in the Earth's crust?

  Metals are found in rocks, often combined with other elements
• What do we call a rock that contains enough metal to make extraction worthwhile?


  An ore
• What happens to ores after they are mined?

  Ores may be concentrated before the metal is extracted and purified
• What is the process involved in handling ores after mining?

  • Ores are mined
  • Concentration of ores may occur
  • Extraction of metal from concentrated ores
  • Purification of extracted metal
• What is the method of extraction for potassium, sodium, calcium, magnesium and aluminium?


  Electrolysis of a molten compound
• What is the method of extraction for zinc, iron and copper?


  Heat an ore with carbon
• What is the method of extraction for gold and silver?


  Found as the uncombined element
• How does the reactivity of metals affect their extraction methods?

  • More reactive metals require electrolysis of molten compounds.
  • Less reactive metals can be extracted by heating ores with carbon.
  • Gold and silver is found in there uncombined form due to low reactivity.
• What is the traditional method of extracting copper from copper sulfide?

  Heating copper sulfide to produce copper and sulfur dioxide
• Why is there a need to extract copper from ores containing smaller amounts of copper compounds?

  Because copper ores are running out
• What is bioleaching?

  A method that uses bacteria grown on low-grade ore to produce a solution containing copper ions
• What is the solution containing copper ions produced by bioleaching called?

  Leachate
• How is copper extracted from the leachate in bioleaching?

  By displacement using scrap iron
• What is the process used to purify copper after extraction from leachate?

  Electrolysis
• Which other metals can be extracted using bioleaching?

  Nickel, cobalt, and zinc
• What is phytoextraction?

  A method that involves growing plants that absorb metal compounds
• What happens to the plants used in phytoextraction after they absorb metal compounds?

  They are burnt to form ash, from which the metal is extracted
• What are the advantages and disadvantages of bioleaching and phytoextraction?

  Advantages:

  • No harmful gases produced
  • Causes less damage to the landscape than mining
  • Conserves supplies of higher grade ores

  
  

  Disadvantages:

  • Very slow process
  • Bioleaching can produce toxic substances and sulfuric acid
  • Phytoextraction is more expensive than mining some ores
  • Growing plants is dependent on weather conditions