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9.3Metals

Alloys and their properties — Cambridge IGCSE Chemistry 0620 Revision Notes & Topical Questions

5 min read 8 parts Lesson 3 of 6 1 quiz

📚 Cambridge IGCSE Chemistry 0620 Hub / Topical Revision
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Lesson summary

9.3 Alloys and their properties — Notes — IGCSE Chemistry notes: Describe alloys, their properties and uses, and explain why they are harder than pure metals.Alloy: a mixture of a metal with other elements, usually other metals and sometimes carbon.Most alloys contain more than o…

  • Stainless steel
  • Most alloys contain more than one metal, and some contain non-metals such as carbon
  • The substances are not chemically combined, so an alloy is a mixture and not a compound
  • Alloys can be stronger, harder and more resistant to corrosion or extreme temperatures than the pure metal
  • These enhanced properties make alloys more useful than pure metals for many jobs
  • The properties of an alloy can be chosen for a job

Section 1 of 8What an alloy is

What an alloy is
Alloy: a mixture of a metal with other elements, usually other metals and sometimes carbon.
Most alloys contain more than one metal, and some contain non-metals such as carbon.
The substances are not chemically combined, so an alloy is a mixture and not a compound.

Section 2 of 8Examples and uses

AlloyMade ofProperties and use
BrassCopper and zincMuch stronger than either metal; musical instruments, ornaments, door knobs
Stainless steelIron with chromium, nickel and carbonHard and resists rusting; cutlery and sinks
SteelIron with a small amount of carbonStronger and harder than iron; buildings and cars
Iron with tungstenIron and tungstenExtremely hard and resists high temperatures
Aluminium alloyAluminium with copper, manganese and siliconStronger but still low density; aircraft bodies

Section 3 of 8Properties of alloys

Properties of alloys
Alloys can be stronger, harder and more resistant to corrosion or extreme temperatures than the pure metal.
These enhanced properties make alloys more useful than pure metals for many jobs.
The properties of an alloy can be chosen for a job.

Section 4 of 8Structure of an alloy

Structure of an alloy
Pure metal: a regular arrangement of identical positive ions in layers in a sea of delocalised electrons.
Alloy: an irregular arrangement, because atoms of different sizes distort the regular lattice.
Particle diagrams show an alloy with uneven-sized particles and distorted layers or rows.

Section 5 of 8Why alloys are harder (Supplement)

Why alloys are harder (Supplement)
In a pure metal the layers slide easily when a force is applied, so the metal is soft and malleable.
In an alloy atoms of a different size are mixed in and disrupt the layers.
The layers can no longer slide easily, so more force is needed and the alloy is harder and stronger.

Section 6 of 8More from the specification

1Chemical resistance of alloys to acids
  • Chemical resistance of alloys to acids adding alloying elements passivates metal surfaces against chemical corrosion caused by dilute mineral acids.
2Periodic
  • Describing properties that repeat at regular intervals along the table
3Metal oxide
  • Compound of a metal and oxygen.
4Metal hydroxide
  • Compound formed when a reactive metal reacts with water.
5Oxygen
  • A gas that relights a glowing splint.
6Hydrogen
  • A gas that gives a squeaky pop with a lighted splint.
7Ductile
  • Able to be drawn into wires.
8Conductor
  • Material that lets heat or electricity flow through it.

Section 7 of 8Key terms

TermMeaning
Alloya mixture of a metal with one or more other elements.
Brassan alloy of copper and zinc.
Stainless steelan alloy of iron with chromium, nickel and carbon that resists rusting.
Steelan alloy of iron with a small amount of carbon.
Mixturesubstances that are not chemically combined.

Section 8 of 8Exam technique

1
Calling an alloy a compoundit is a mixture of a metal with other elements.
2
Saying alloys are harder because the bonds are stronger: different-sized atoms stop the layers sliding.
3
Choosing the particle diagram with identical particles in neat rows for an alloy: an alloy has uneven-sized particles.
4
Saying all alloys contain only metalssome contain carbon.

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