Metal Properties and Reactivity

This guide covers Topic 9, Metals — subtopics 9.1 Properties of metals, 9.4 Reactivity series and 9.5 Corrosion of metals — for Cambridge IGCSE Chemistry 0620 and Cambridge O Level Chemistry 5070, 2026–2028 series. The remaining Topic 9 subtopics — uses, alloys and extraction — are covered in Alloys and Extraction of Metals.

Where this fits in 0620/5070

This is the topic where earlier ideas about bonding (Topic 2) and redox (Topic 6.4) become predictive tools: once you know where a metal sits in the reactivity series, you can predict whether it reacts with water, steam or dilute acid, and whether it will displace another metal from solution — without needing to be told the answer or memorise individual reactions one at a time.

Syllabus coverage

CAMBRIDGE IGCSE CHEMISTRY 0620

Core

• Comparing the general physical properties of metals and non-metals: thermal conductivity, electrical conductivity, malleability/ductility, melting and boiling points (9.1)
• Describing the general chemical properties of metals — reactions with dilute acids, cold water/steam, and oxygen (9.1)
• Stating the order of the reactivity series: potassium, sodium, calcium, magnesium, aluminium, carbon, zinc, iron, hydrogen, copper, silver, gold (9.4)
• Describing the reactions (if any) of potassium/sodium/calcium with cold water, magnesium with steam, and magnesium/zinc/iron/copper/silver/gold with dilute hydrochloric acid, explained by position in the series (9.4)
• Deducing an order of reactivity from given experimental results (9.4)
• Stating the conditions required for iron/steel to rust (hydrated iron(III) oxide), and common barrier methods — painting, greasing, coating with plastic (9.5)
• Explaining how barrier methods prevent rusting, by excluding oxygen or water (9.5)

9.1 has no Extended-only content at all — every 9.1 outcome above is Core, for every 0620 candidate.

Supplement / Extended

• Describing relative reactivity in terms of a metal’s tendency to form positive ions, using displacement reactions with aqueous magnesium, zinc, iron, copper and silver ions (9.4)
• Explaining aluminium’s apparent unreactivity in terms of its protective oxide layer (9.4)
• Describing zinc galvanising as both a barrier method and sacrificial protection, and explaining sacrificial protection in terms of the reactivity series and electron loss (9.5)

CAMBRIDGE O LEVEL CHEMISTRY 5070

5070 has no Core/Extended split — every outcome above, Core and Supplement alike, is required for every O Level candidate.

Physical and chemical properties of metals

Metals share a recognisable set of physical properties: good thermal and electrical conductivity, malleability (can be hammered into shape without shattering) and ductility (can be drawn into wires), and generally high melting and boiling points. These properties come directly from metallic bonding — a lattice of positive ions in a “sea” of delocalised electrons, covered in Ionic, Covalent and Metallic Bonding.

Chemically, metals are compared by how they react with three things: dilute acids (more reactive metals react faster, releasing hydrogen), cold water or steam (very reactive metals react with cold water; moderately reactive ones need steam), and oxygen (forming a metal oxide, at a rate that again depends on reactivity).

The reactivity series

The reactivity series ranks metals from most to least reactive:

potassium > sodium > calcium > magnesium > aluminium > carbon
  > zinc > iron > hydrogen > copper > silver > gold

Carbon and hydrogen are included even though they aren’t metals — they act as useful reference points (carbon for extraction methods, hydrogen for whether a metal reacts with dilute acid at all).

Reaction with water/steam, by position:

• Potassium, sodium, calcium react with cold water, releasing hydrogen and forming a hydroxide.
• Magnesium reacts only with steam (not cold water at a noticeable rate), forming magnesium oxide and hydrogen. This is the only steam reaction the syllabus requires.
• Zinc and iron react with steam only, and slowly — not required by the syllabus, but factually true, so don’t mark it wrong if it comes up.
• Copper, silver, gold — no reaction with cold water or steam at this level.

Reaction with dilute hydrochloric acid, by position: magnesium and zinc react readily; iron reacts more slowly; copper, silver and gold — all below hydrogen — do not react with dilute acid at all.

Worked example. Magnesium ribbon reacts vigorously with dilute hydrochloric acid; iron filings react slowly, with gentle fizzing; copper powder shows no visible reaction. Place the three metals in order of reactivity, with reasoning.

More vigorous reaction with dilute acid = more reactive metal.
Magnesium (fastest) > Iron (slow) > Copper (none)

This matches their positions in the reactivity series:
Mg is well above Fe, and Fe is above hydrogen while Cu is below it —
consistent with copper showing no reaction at all.

Displacement reactions

A more reactive metal will displace a less reactive metal from a solution of its salt — the more reactive metal loses electrons to form ions in solution (is oxidised), while the less reactive metal’s ions gain electrons and are deposited as solid metal (are reduced). This is direct, experimental evidence for the reactivity series, rather than something to memorise separately from it.

Worked example. An iron nail is placed in blue aqueous copper(II) sulfate. Describe and explain what happens.

Iron is more reactive than copper, so iron displaces copper:
Fe(s) + CuSO4(aq) → FeSO4(aq) + Cu(s)

Observation: the nail becomes coated in a pink-brown deposit (copper metal);
the blue solution fades to the pale green of iron(II) sulfate.

Aluminium’s apparent unreactivity

Aluminium sits above zinc and iron in the reactivity series, so it should react more readily with acids, water and oxygen than either — yet in everyday use it appears almost unreactive. The explanation is a thin, continuous layer of aluminium oxide that forms instantly on the metal’s surface on contact with air. This oxide layer is impermeable — it seals the aluminium underneath from further contact with oxygen, water or acid — and it is also self-repairing: if the surface is scratched, the freshly exposed aluminium immediately reacts with air to form a new oxide layer. Once the oxide layer is removed or prevented from forming (for example by scratching the metal under mercury), aluminium reacts with the expected vigour for its position in the series.

Corrosion and its prevention

Rusting is the corrosion of iron and steel, forming hydrated iron(III) oxide — it needs both oxygen and water present; remove either one and rusting stops.

Barrier methods work simply by keeping oxygen and water away from the metal surface: painting, greasing, and coating with plastic all physically exclude the two things rusting needs.

Galvanising — coating steel with zinc — is a barrier method and something more: even where the zinc coating is scratched and the steel underneath is exposed, the steel still doesn’t rust. This is sacrificial protection: zinc is more reactive than iron, so the zinc corrodes preferentially, losing electrons in place of the iron, protecting it even without an intact physical barrier.

Common mistakes

• Assuming all metals react with cold water. Only potassium, sodium and calcium do, at this level — magnesium needs steam. (Zinc and iron also react with steam, slowly, though this isn’t syllabus-required; copper, silver and gold show no reaction with cold water or steam at all.)
• Explaining a displacement reaction without mentioning electron transfer. “Iron displaces copper because it’s more reactive” is incomplete at Extended/O Level — the expected explanation is in terms of the more reactive metal losing electrons more readily to form ions.
• Confusing a barrier method with sacrificial protection. Every sacrificial coating is also acting as a barrier while it’s intact — but sacrificial protection is specifically the extra effect that continues working even once the barrier is broken.
• Forgetting that rusting needs BOTH oxygen and water. A common wrong answer removes only one condition; both are required, and either one being absent is sufficient to prevent rusting.

Quick revision checklist

• General physical and chemical properties that distinguish metals from non-metals
• The reactivity series, in order, from memory
• Which metals react with cold water, which need steam, and which don’t react with either
• Reactions (or lack of reaction) with dilute hydrochloric acid, by position in the series
• (0620 Extended, 5070 required) explaining displacement reactions in terms of electron transfer
• (0620 Extended, 5070 required) aluminium’s apparent unreactivity, and why
• Conditions needed for rusting, and how barrier methods prevent it
• (0620 Extended, 5070 required) sacrificial protection, explained in terms of reactivity and electron loss

Related resources

• Alloys and Extraction of Metals — uses, alloys and extraction, the rest of Topic 9
• Ionic, Covalent and Metallic Bonding — the metallic bonding behind these physical properties
• Redox Reactions — electron transfer, applied here to displacement and sacrificial protection
• Cambridge IGCSE Chemistry hub · Cambridge O Level Chemistry hub

Written against Cambridge IGCSE Chemistry 0620 and Cambridge O Level Chemistry 5070, 2026–2028 series. Always check the current syllabus for your examination year.