C10.1 Properties of metals
Why do we make alloys instead of using pure metals?
Research each of the six alloys below. For every one, find its composition, its key properties, a specific use, and explain why it's better than the pure metal it replaces.
30 minutes · pairs or individual
For each alloy, answer these four questions
Q1What is it made of? (all components)
Q2What are its key physical properties?
Q3What is a specific use — and why is it used for that?
Q4Why is the alloy better than the pure metal for that job?
Steel
Fe + C
construction beams, car bodies, tools
Stainless steel
Fe + Cr (+ Ni)
surgical tools, cutlery, sinks
Brass
Cu + Zn
musical instruments, taps, locks
Bronze
Cu + Sn
statues, ship propellers, medals
Solder
Sn + Pb (or Sn + Ag)
joining electronic components, plumbing
Nichrome
Ni + Cr
toaster elements, electric fire coils, kilns
Key concept — why alloying changes properties
Pure metal lattice
In a pure metal, all atoms are the same size, arranged in a regular pattern. Layers of atoms can slide over each other easily when a force is applied — this is why pure metals are soft and malleable.
- All atoms identical size
- Regular close-packed layers
- Layers slide easily
- Relatively soft and malleable
Exam tip: recognise the pure metal diagram — equal-sized spheres in a regular arrangement.
Alloy lattice
Adding a different-sized atom disrupts the regularity of the lattice. The layers can no longer slide as easily. This makes the alloy harder and stronger than the pure metals it contains.
- Different-sized atoms present
- Irregular arrangement
- Layers cannot slide freely
- Harder and stronger
Exam tip: in the diagram, look for an atom that is clearly a different size — that's how you identify the alloy.
Useful starting points