Alloy

  1. An alloy is a mixture of two or more metals mixed in a certain percentage.
  2. Most pure metals are weak and soft. The properties of pure metals can be improved by making them into alloys.
  3. Alloys are made to
    1. increase the hardness of metals.
      Example:
      Magnalium is made from aluminium and magnesium to improve the hardness of the pure metals but at the same time, maintaining their lightness.
    2. prevent the corrosion of metals.
      Stainless steel which can resist rusting is made by adding carbon, chromium and nickel to iron.
    3. improve the beauty and lustre of metals.
      Copper and antimony added to tin produces pewter, used to make decorative items.

Q & A

Q: Explain why alloy of copper is harder than pure copper?
A:

  1. In alloys of copper, foreign atoms are present. 
  2. The impurities can prevent the layers of copper atoms slide over each others, thus making the metals harder, less malleable and ductile.
(Pure metal - Atoms can slide over each other easily)
(Alloy - The presence of foreign atoms prevent the atoms of metal slide over each other)


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