IGCSE Chemistry — Metals: Notes, Practice Questions & Worked Solutions

IGCSE Chemistry 0620 · Topic 9: Metals

Metals

How reactive a metal is decides almost everything about it: how it reacts with water and acid, whether it corrodes, and even which extraction method is used to obtain it from its ore.

1. The Reactivity Series

Potassium > Sodium > Calcium > Magnesium > Aluminium > (Carbon) > Zinc > Iron > (Hydrogen) > Copper > Silver > Gold

Carbon and hydrogen are included as reference points (non-metals), since they help decide extraction methods and predict reactions.

Worked example — using the reactivity series Magnesium is added to a solution of copper(II) sulfate. Predict what happens.
Magnesium is more reactive than copper, so it displaces copper from the solution: Mg + CuSO₄ → MgSO₄ + Cu. The blue solution fades as copper metal is deposited.

2. Extraction of Metals

The extraction method depends on the metal’s position in the reactivity series:

Reactivity	Extraction method	Example
More reactive than carbon	Electrolysis of a molten compound	Aluminium (from molten aluminium oxide in cryolite)
Less reactive than carbon	Reduction with carbon	Iron (in the blast furnace)

Extraction of iron (blast furnace) Iron ore (haematite, Fe₂O₃) is reduced by carbon monoxide, formed from coke burning in the furnace: Fe₂O₃ + 3CO → 2Fe + 3CO₂

3. Rusting and Alloys

Rusting of iron requires both water and oxygen. Prevention methods include painting/coating (barrier methods) and galvanising (coating with zinc, which also provides sacrificial protection — zinc corrodes in preference to iron, since it is more reactive).

Alloys (mixtures of a metal with other elements) are usually harder and stronger than the pure metal, because the different-sized atoms disrupt the regular layers, making it harder for them to slide over each other.

Common mistakes to watch for

Forgetting rusting needs BOTH water and oxygen — removing either one prevents it.
Mixing up which metals need electrolysis vs carbon reduction — the key dividing line is reactivity compared to carbon.
Describing galvanising as “just a coating” — its real value is sacrificial protection, which still protects the iron even if the zinc layer is scratched.

Key Vocabulary Recap

Reactivity series — an ordered list of metals by how readily they react

Alloy — a mixture of a metal with one or more other elements

Sacrificial protection — a more reactive metal corrodes in preference to protect a less reactive one

Syllabus Reference

This note covers IGCSE Chemistry 0620 Topic 9, Metals: physical/chemical properties, alloys, the reactivity series, corrosion and rusting, extraction of iron, and extraction of aluminium.

Practice questions

IGCSE Chemistry 0620 · Topic 9: Metals — Practice Question Bank (no answers)

Metals — Practice

Covers: the reactivity series, extraction, rusting, and alloys. 10 questions.

Q1 Core

State the order of reactivity of potassium, calcium, copper, and zinc, from most to least reactive.

Q2 Core

Magnesium is added to a solution of copper(II) sulfate. Predict what you would observe, and write the symbol equation.

Q3 Core

State the two conditions needed for iron to rust.

Q4 Core

Explain how galvanising protects iron, even if the zinc coating gets scratched.

Q5 Extended

Explain why aluminium is extracted by electrolysis but iron is extracted by reduction with carbon.

Q6 Core

Write the equation for the reduction of iron(III) oxide by carbon monoxide in the blast furnace.

Q7 Core

Explain, in terms of structure, why alloys are generally harder than pure metals.

Q8 Core

Name one common alloy and state its two main components.

Q9 Core

State the observation and write a word equation for the reaction between zinc and dilute hydrochloric acid.

Q10 Core

Explain why gold is found in the Earth as the pure, uncombined element, unlike most other metals.

Worked solutions

Show worked solutions

IGCSE Chemistry 0620 · Topic 9: Metals — Solutions

Metals — Practice: Solutions

Order K, Ca, Cu, Zn by reactivity.

✓Potassium > Calcium > Zinc > Copper (most to least reactive)

Mg + CuSO₄ solution.

✓The blue solution fades to colourless, and a reddish-brown solid (copper) forms, as magnesium (more reactive) displaces copper. Mg + CuSO₄ → MgSO₄ + Cu

Two conditions for rusting.

✓Water (moisture) and oxygen (air) are both needed.

Why does galvanising still work if scratched?

✓Zinc is more reactive than iron, so it corrodes in preference to the iron underneath (sacrificial protection) — even where the coating is scratched and the iron is exposed, the zinc still corrodes first, protecting the iron.

Why Al by electrolysis, Fe by carbon reduction?

✓Aluminium is more reactive than carbon, so carbon cannot remove oxygen from aluminium oxide — electrolysis is needed instead. Iron is less reactive than carbon, so carbon can reduce iron oxide to iron directly, which is a cheaper method than electrolysis.

Blast furnace reduction equation.

✓Fe₂O₃ + 3CO → 2Fe + 3CO₂

Why are alloys harder than pure metals?

✓A pure metal has regular layers of same-sized atoms, which can slide over each other relatively easily. In an alloy, atoms of a different element (a different size) disrupt this regular layered structure, making it harder for the layers to slide — so alloys are generally harder and stronger.

Name an alloy and its components.

✓Any valid example, e.g. brass (copper and zinc), bronze (copper and tin), or steel (iron and carbon).

Zn + dilute HCl.

✓Bubbles of gas (hydrogen) are observed, and the zinc gradually dissolves. zinc + hydrochloric acid → zinc chloride + hydrogen

Q10

Why is gold found uncombined?

✓Gold is extremely unreactive (very low down the reactivity series), so it does not readily react with oxygen, water, or other substances in the environment to form compounds — it remains as the pure element.

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