Alloy Structure — Examination Paper
15 questions · 38 marks · Cambridge IGCSE Chemistry 0620 (2026–2028)
The two diagrams below represent the atomic structure of a pure metal and an alloy. Identify which diagram represents an alloy and explain how you can tell.
A student is given two unlabelled diagrams of metallic structures. One shows all circles the same size in neat rows. The other shows large and small circles disrupting the pattern. Which is the alloy? Explain your reasoning.
Look at the structural diagram of brass (an alloy of copper and zinc). Describe TWO observable differences between this diagram and a diagram of pure copper.
A diagram shows rows of atoms with one row shifted out of alignment due to a differently-sized atom. Is this a pure metal or an alloy? State the evidence from the diagram.
Steel is an alloy of iron and carbon. Draw and label a diagram showing the atomic structure of steel. Your diagram must clearly show why steel is harder than pure iron.
Explain, in terms of their structure, why alloys are harder than pure metals. [3]
Pure metals are described as malleable. Explain, using atomic structure, what this means and why alloys are less malleable than pure metals. [3]
Bronze is an alloy of copper and tin. Explain why bronze is harder than pure copper. [3]
A student claims: 'Alloys are harder because the bonds between atoms are stronger.' Assess this statement. Is the student correct? Give the scientifically accurate explanation. [3]
Nitinol is a shape-memory alloy made from nickel and titanium. Using your knowledge of alloy structure, explain why nitinol is harder than either pure nickel or pure titanium. [3]
Pure iron is described as 'too soft' for use in construction. Explain how its structure is modified to make it harder and more suitable for building bridges and skyscrapers. [3]
Gold jewellery is rarely made from pure (24-carat) gold. Instead, 18-carat gold is used, which is an alloy containing 75% gold and 25% other metals. Suggest why 18-carat gold is preferred for jewellery over pure gold. [2]
A manufacturer wants to create a metal that: (i) conducts electricity, (ii) is harder than pure copper, and (iii) resists corrosion. Suggest how they could achieve this and explain the structural reason for the increased hardness. [3]
Duralumin is a lightweight alloy of aluminium and copper used in aircraft. State TWO reasons why duralumin is more suitable for aircraft construction than pure aluminium. [2]
A student suggests that 'to make a metal harder, you should remove some atoms from the lattice to create gaps.' Evaluate this suggestion using your knowledge of alloy structure. [2]
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