IGCSE Chemistry – Metals: Quick Revision Notes

Physical Properties of Metals vs Non-Metals

  • Metals:
    • Lose electrons → \text{M}^{n+} ions
    • Good conductors of heat & electricity
    • Malleable (hammered) & ductile (drawn into wires)
    • High melting / boiling points
  • Non-metals:
    • Gain / share electrons → \text{X}^{n-} ions or covalent bonds
    • Poor conductors (except graphite)
    • Brittle solids, low m.p./b.p.

Chemical Properties of Metals

  • React with oxygen → metal oxides (often basic)
    \text{Metal} + O_2 \rightarrow \text{Metal oxide}
  • React with cold water (very reactive metals) → metal hydroxide + H2 2K + 2H2O \rightarrow 2KOH + H_2
  • React with steam (moderately reactive metals) → metal oxide + H2 Mg + H2O(\text{g}) \rightarrow MgO + H_2
  • React with dilute acids → salt + H2 \text{Metal} + 2HCl \rightarrow \text{Metal chloride} + H2
  • Speed of reaction indicates position in reactivity series.

Reactivity Series & Displacement

Most → Least reactive:
K > Na > Ca > Mg > Al > C > Zn > Fe > H > Cu > Ag > Au

  • More reactive metal displaces a less reactive metal from its salt:
    Fe + CuSO4 \rightarrow FeSO4 + Cu (because Fe above Cu)
  • Reactivity = ease of electron loss → positive ions.
  • Aluminium appears unreactive due to a protective Al2O3 layer.

Metals with Water, Steam & Acids (Quick Guide)

  • Cold water: K, Na, Ca (vigorous → slow)
  • Steam: Mg, Zn, Fe (react; no reaction with cold water)
  • Dilute HCl/H2SO4: Mg > Zn > Fe (rate decreases); Cu, Ag, Au no reaction.

Uses of Selected Metals

  • Aluminium: aircraft & overhead cables (low density, good conductivity, corrosion-resistant)
  • Aluminium: food containers (oxide layer resists corrosion)
  • Copper: electrical wiring (excellent conductivity & ductility)

Alloys

  • Definition: mixture of a metal with other element(s).
    • Brass = Cu + Zn
    • Stainless steel = Fe + Cr (+ Ni, C)
  • Structure: different-sized atoms disrupt layers → layers cannot slide → harder & stronger than pure metal.
  • Uses: stainless steel cutlery (hard, corrosion-resistant).

Corrosion & Rust Prevention

  • Rusting of iron requires: water + oxygen → hydrated Fe2O3
  • Barrier methods: painting, greasing, plastic coating (exclude H2O/O2)
  • Galvanising: coat iron with zinc.
    • Barrier + sacrificial protection.
    • Zinc is higher in reactivity series → loses electrons first, protecting iron.
  • Sacrificial protection: attach a more reactive metal (e.g.
    zinc blocks on ships) so it corrodes instead of iron/steel.