AQA Chemistry 1 C1.3

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  • Created by: Chloe
  • Created on: 06-06-13 20:35

Extracting Metals - Carbon Reduction

  • An ore is a rock containing enough metal to make it economically viable to extract it.
  • Ores are mined and may be concentrated before the metal is extracted and purified.
  • Most metals are found in compound so reactions are needed to extract the element.
  • Some metals are pure such as gold which is found without a compound in the earth. This is known as the metal in its native state.
  • Metals that are less reactive than carbon can be extracted with reduction by carbon.
  • This is where carbon pushes the metal out of the compound and takes it's place.
  • This is commonly used to extract iron in a blast furnace, where iron oxide and carbon is reduced to iron and carbon dioxide.
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Extracting Metals - Electrolysis

  • The other way of extracting metals is electrolysis. This is used when the metal is more reactive that carbon.
  • First, the atoms need to be free to move around so the ore is melted, known as smelting, or added to a solution.
  • Then electricity is passed through the substance with the use of positive and negative electrodes.
  • The positive ions in the substance are attracted to the negative electrode and the negative ions are attracted to the positive electrode.
  • The ions attracted to the negative electrode are the pure forms of the metal.
  • This process is used for extracting copper.
  • Unfortunately, the large amounts of energy needed for the process makes it expensive.
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Extracting Metals - New Techniques

  • Due to the rapid decline of remaining copper rich ores, we need to find new ways of getting copper.
  • One way is Phytomining. This involves plants which take up copper in their roots. The plants can be burnt to produces ashes containing copper compounds.
  • The other technique is Bio-leaching. This uses bacteria that produce leachate solutions containing the metal compounds. This can then be extracted.
  • The final technique is the use of scrap iron. Scrap iron can be used to displace copper in a similar way to carbon displaces iron.
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Extracting Metals - Recycling

  • Certain metals are very expensive to extract as they cannot be extracted by carbon and longer methods with more energy needed are necessary.
  • Aluminium and Titanium are two metals that have to be extracted in alternative ways, hence they are so expensive.
  • A way to avoid extracting metals is to recycle them.
  • Recycling avoids using up limited resources and avoids major expense in terms of energy and the affects on the environment.
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Alloys

  • An alloy is a mixture of multiple elements that together improve the properties of the metal.
  • For example, steel is an alloy of iron.
  • Iron straight from the blast furnace is 96% iron and the impurities make it brittle and so it cannot be used for a lot of things.
  • Steels are mixtures of iron and carbon.
  • Low-carbon steels are soft and easily shaped whereas high-carbon steels are hard. Stainless steels are resistant to corrosion.
  • Most everyday metals are alloys as they are too soft for many uses. For example, pure copper, gold, iron and aluminium.
  • An alloy is stronger because different metals have atoms of different sizes. Therefore, it prevents the atoms from sliding over each other easily.
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Properties and Uses of Metals

  • The elements is the central block of the periodic table (between groups 2 and 3) are the transition metals.
  • Like other metals, they are good conductors (heat and electricity) and can be re-shaped.
  • They are commonly used for building structures and for building things that require heat and electricity to pass through them easily.
  • Copper is a transition metal. It is useful for wiring and plumbing because:
    • It is a good conductor of electricity and heat
    • It can be bent but is still strong
    • It does not react with water
  • Aluminium and titanium are useful metals because:
    • They have a low density
    • They are resistant to corrosion
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