Properties of Metals
Section: 9. Metals | Syllabus: Cambridge IGCSE Chemistry (0620)
Physical Properties: Metals vs. Non-Metals
Metals share a set of characteristic physical properties, all traceable to the same cause: a metal is a lattice of positive ions surrounded by a "sea" of delocalised electrons.
| Property | Metals | Non-metals |
|---|---|---|
| Thermal conductivity | good conductors of heat | poor conductors (insulators) |
| Electrical conductivity | good conductors of electricity | poor conductors (insulators) |
| Malleability & ductility | malleable (hammered into shape) and ductile (drawn into wires) | brittle if solid - shatter rather than bend |
| Melting & boiling points | usually high | usually low |
Worked Example
- Question: state two physical properties that are typical of metals but not of non-metals. [2]
- Answer: any two of - good electrical conductivity; good thermal conductivity; malleable (can be hammered into shape); ductile (can be drawn into wires)
Common Mistakes
- ❌ Listing "high density" or "shiny/lustrous" as one of the compared physical properties
- ✓ the syllabus comparison is limited to four properties: thermal conductivity, electrical conductivity, malleability & ductility, and melting/boiling points - density and appearance are not part of this specific comparison, even though they are true generalisations about metals
Chemical Properties of Metals
The general chemical properties of metals are limited to their reactions with dilute acids, cold water and steam, and oxygen. Whether and how vigorously a given metal reacts with each depends on its position in the reactivity series (covered in the next topic).
1. Reaction with Dilute Acids
Metals above hydrogen in the reactivity series react with dilute acids to give a salt and hydrogen gas:
metal + acid → salt + hydrogen
Zn(s) + H₂SO₄(aq) → ZnSO₄(aq) + H₂(g)
2. Reaction with Cold Water and Steam
The most reactive metals (potassium, sodium, calcium) react with cold water to give a metal hydroxide and hydrogen. Less reactive metals such as magnesium react far too slowly with cold water to be useful, but react readily with steam to give a metal oxide and hydrogen instead:
2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g)
Mg(s) + H₂O(g) → MgO(s) + H₂(g)
3. Reaction with Oxygen
Most metals react with oxygen to form a metal oxide, which is basic:
2Mg(s) + O₂(g) → 2MgO(s)
Common Mistakes
- ❌ Writing "metal + water → metal oxide + hydrogen" for a reactive metal like sodium reacting with cold water
- ✓ cold water gives a metal hydroxide (2Na + 2H₂O → 2NaOH + H₂); it's only the reaction with steam that gives the metal oxide
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