The Aluminium Shield: Oxide Layer Mastery
15 Questions · 29 Total Marks · Hidden Mark Schemes
🔍 The Central Paradox
Aluminium sits above iron in the reactivity series — it is genuinely more reactive. Yet iron rusts and crumbles while aluminium stands firm for decades.
The answer? A microscopic suit of armour: the aluminium oxide (Al₂O₃) layer.
The reactivity series ranks metals by how readily they react. Use this to answer the question below.
Where is aluminium placed in the reactivity series compared to iron?
A student drops a piece of aluminium into dilute hydrochloric acid. Surprisingly, almost nothing happens. What is the most likely reason for this observation?
Iron rusts when exposed to air and water, eventually crumbling to dust. Aluminium, despite being more reactive, does NOT corrode in the same way. What property of aluminium oxide explains this?
State TWO everyday uses of aluminium that rely on its apparent unreactivity (resistance to corrosion).
Name the compound that forms on the surface of aluminium when it is exposed to air.
Explain why aluminium appears to be unreactive, even though it is above iron in the reactivity series. [2]
A student claims: 'Aluminium must be less reactive than iron because iron rusts but aluminium does not corrode.' Explain why the student's conclusion is INCORRECT. [2]
What is the purpose of the anodising process applied to aluminium?
Write a word equation AND a balanced symbol equation (with state symbols) for the reaction of aluminium with oxygen. [3]
Explain why iron corrodes more severely than aluminium over time, even though iron is LESS reactive than aluminium. [2]
The surface of a piece of aluminium is heavily scratched under water. Describe what you might observe, and explain your observations. [2]
A technician mixes aluminium powder with mercury(II) chloride solution. After a few minutes, the aluminium starts to react vigorously with the surrounding air, forming white fluffy solid rapidly. Suggest an explanation for this behaviour. [2]
A student wants to extract aluminium from aluminium oxide by reducing it with carbon (as is done with iron from iron ore). Explain why this method does NOT work for aluminium, and state the method actually used to extract aluminium. [3]
Aluminium is used to make overhead electricity cables, despite the fact that copper is a better electrical conductor. Suggest TWO reasons why aluminium is preferred over copper for this application. [2]
EXTENDED RESPONSE: Compare the corrosion of aluminium and iron. In your answer, refer to the reactivity of each metal, the properties of the oxide layer formed, and the consequences for long-term durability. [4]
⚡ THE THREE GOLDEN RULES — Aluminium's Oxide Layer
RULE 1: Aluminium IS reactive — it is ABOVE iron in the reactivity series.
RULE 2: It appears unreactive because of a thin, dense, impermeable layer of aluminium oxide (Al₂O₃).
RULE 3: The oxide layer PREVENTS oxygen, water, and acids from reaching the metal underneath. [2 marks every time]
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