GCSE Chemistry – Extraction of Metals

Extracting metals

  • Ores contain enough metal to make it economical to be extracted. The economics of extraction can change over time.
  • Ores are mined and may be concentrated before they are extracted and purified.
  • Unreactive metals such as gold are found in the Earth itself.
  • Some metals are found as compounds and require chemical reactions to extract the metal.

 

The process of extraction

  • Metals that are less reactive than carbon can be extracted from their oxides by reduction (removal of oxygen) with carbon.
  • Iron oxide is reduced in the blast furnace to make iron.
  • Metals that are more reactive than carbon e.g aluminium is extracted by electrolysis of molten compounds.
  • Electrolysis uses large amounts of energy and can therefore be expensive.

 

Extracting copper

  • Copper can be extracted from copper-rich ores by heating ores in a furnace (smelting).
  • The copper can be purified by electrolysis. The supply of copper-rich ores is limited.
  • Copper is extracted from its ores using chemical processes that involve heat or electricity.
  • Copper-rich ores are being used up and traditional mining and extraction have major environmental impacts.

 

New ways of extracting copper

  • New ways are being found to extract copper from low-grade ores to reduce the environmental impacts of traditional mining.
  • Bioleaching uses bacteria to produce leachate solutions containing metal compounds

Phytomining uses plants to absorb metal compounds and the plants are burned used to produce an ash which contains metal compounds

  • Copper can be extracted from solutions containing copper salts by electrolysis or by displacement (more reactive pushes out less reactive) using scrap iron.

 

  • Aluminium and titanium can’t be extracted from their oxides by reduction with carbon.
  • Current methods of extraction are expensive because 1) there are many stages involved 2) there is a lot of energy involved.

 

Recycling metals

  • We should recycle metals because we are extracting them from limited resources and it is expensive in terms of energy and effects on the environment.

 

Alloy

  • Iron from the blast surface contains about 96% iron. The impurities make it brittle so it has limited uses
  • Blast furnace iron is used as cast iron because of its strength in compression
  • Most iron is converted into steels.
  • Steels are alloys since they used mixtures of carbon and iron
  • Some steels contain other metals. Alloys can be designed to specific uses.
  • Low-carbon steels are easily shaped, high carbon steels are hard, and stainless steels are resistant to corrosion.
  • Most metals in everyday uses are alloys. Pure copper, gold, iron and aluminium are all too soft for everyday uses and so are mixed with small amounts of similar metals to make them harder for everyday use.

 

Properties and uses of metals

  • Metals in the centre of the periodic table are transition metals. They are conductors of heat and electricity and can be bent or hammered into shape.
  • They are useful for structural metals and for making things which must allow heat or electricity to pass through them easily
  • Copper has properties that make it useful for wiring and plumbing:

-it’s a good conductor of electricity and heat

-Can be bent but is hard enough to be used to make pipes or tanks

-does not react with water