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10.3Unit 5: Metals, non-metals, acids and alkalis

Metal mixtures

5 min read 4 parts Lesson 3 of 7 1 quiz

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Part 1 of 4What is an alloy

1Alloy
= a mixture of metals, made by mixing different metals and melting them
2Atoms
— the atoms of the different metals mix but do not bond together
3Properties1 point
— differ from those of the metals in the alloy
  • Bronze, copper plus tin, is harder than either metal.
4Steel1 point
— an alloy of iron and carbon, much harder than pure iron
  • With chromium and nickel it does not rust and is used for cutlery.

Part 2 of 4Why alloys are harder

  • Pure metal — atoms are the same size in regular rows, and layers slide over each other easily
  • Alloy — a different-sized atom disrupts the regular pattern
    • The layers cannot slide as easily.
    • The alloy is harder and stronger than the pure metal.

Part 3 of 4Uses of alloys

AlloyMade fromUse
CoinsCopper and nickel (silver-coloured); copper, zinc and tin (copper-coloured)Hardwearing but malleable enough to stamp
Gold jewelleryGold and copper (18 carat: 18 parts of 24 gold)Stronger than pure gold
DuraluminAluminium, magnesium and copperAeroplanes; about five times stronger than aluminium
Titanium alloysTitanium with other metalsArtificial joints
NitinolNickel and titaniumShape memory glasses frames

Part 4 of 4Brass and bronze

AlloyMade fromProperties and uses
BrassCopper and zincGolden, resistant to corrosion; musical instruments, plumbing
BronzeCopper and tinHard, corrosion resistant; sculptures, bells, cymbals, ship fittings
  • Melting point — alloys melt over a range because the proportions of metals vary

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