4CH1

Extraction and Uses of Metals

Inorganic Chemistry

Exam Frequency Analysis

Past paper frequency (2018 to 2024)

This topic accounts for approximately 6% of your exam marks.

stable
Low
Stable6%

Blast furnace chemistry and electrolytic extraction of aluminium regularly examined.

What an alloy is

  • An alloy is a mixture of a metal with one or more other elements, usually another metal or a non-metal such as carbon
  • Examples already encountered:
    • Steel: iron + carbon (see section 3)
    • Brass: about 70% copper + 30% zinc — used for fittings, decorative work and musical instruments
    • Bronze: copper + tin — used for statues, bells and bearings

Why alloys are harder than the pure metal

  • Pure metals deform easily because layers of identical-size atoms slide cleanly over one another (this was the malleability argument in topic 08)
  • In an alloy, the added element has atoms of a different size, which disrupts the regular layered packing
  • The disrupted layers can no longer slide smoothly, so the alloy is harder and more rigid
  • Many alloys are also chosen because they resist corrosion (stainless steel, bronze) or tolerate higher temperatures (nichrome heating elements)
  • The detailed structural picture sits in topic 08 Metallic Bonding, section 3
Particle arrangement in an alloy: large atoms of element X packed together with smaller atoms of element Y scattered among them, disrupting the regular layers
Source: Alloys by Save My Exams
Exam tip

Explain why an alloy is harder (less malleable) than the pure metal

What comes up: a 2–3-mark question asking you to use a diagram of particle arrangement to explain why an alloy is harder or less malleable than the pure metal.

Write (three marks): (1) in the pure metal, layers of atoms slide over one another easily; (2) in the alloy, atoms of a different size disrupt the regular arrangement; (3) this disruption prevents the layers from sliding, making the alloy harder.

Watch out: the mark scheme deducts a mark if you never mention layers/rows/sheets of atoms — you must use that language. It also rejects "molecules", "intermolecular forces", "ionic bonds", or "covalent bonds" as the reason layers cannot slide; stick to atoms/cations and their arrangement. Saying the metallic bonds are stronger is explicitly ignored.