🔩 Rusting & Corrosion — Paper 2 & 6 Exam
Cambridge IGCSE Chemistry 0620 · Core & Supplement · 15 Questions
Examiner's Brief: Rusting is one of the most common sources of lost marks. Students confuse "corrode" with "rust", forget that BOTH water and oxygen are needed, and give the wrong chemical name. In this exam, precision earns marks.
Conditions for Rusting
Core recall — name the conditions, name the product.
State the two conditions required for the rusting of iron.
Give the full chemical name for rust.
A student says 'iron rusts faster near the sea.' Suggest TWO reasons why this statement is chemically correct.
⭐ [Supplement] Explain, in terms of oxidation and reduction, what happens to iron atoms during rusting.
A nail is left in a dry atmosphere containing oxygen but no water vapour. Will it rust? Explain your answer.
The Classic Rusting Experiment
Experimental design & Paper 6 analysis skills.
In a rusting experiment, Tube 1 contains boiled water with a layer of oil on top. State the purpose of: (a) boiling the water, and (b) the layer of oil.
Tube 2 in the rusting experiment contains a nail in anhydrous calcium chloride (a drying agent) with no liquid water. State the purpose of the anhydrous calcium chloride, and predict whether the nail in Tube 2 will rust.
A student sets up three test tubes to investigate rusting: Tube A (nail in air + water), Tube B (nail in boiled water + oil), Tube C (nail in dry air with CaCl₂). Complete the results table: which tube shows rusting, and what does this experiment prove?
⭐ [Supplement] A student adds sodium chloride solution to one of the test tubes instead of pure water. Predict and explain the effect on the rate of rusting.
Suggest why iron railings near a swimming pool rust faster than identical railings in a dry inland area.
Terminology & Misconceptions
Examiner traps — only iron rusts; other metals corrode.
A student states 'the copper water pipe rusted after years of use.' Why is this statement scientifically incorrect? Give the correct term for what happened to the copper pipe.
Is rusting a physical change or a chemical change? Justify your answer.
Explain why painting an iron gate prevents rusting, and suggest what might happen if the paint is scratched.
⭐ [Supplement] Explain why connecting a piece of magnesium to an iron gate prevents rusting, even if the iron surface is exposed to water and oxygen.
A ship's hull is made of steel. Suggest THREE different methods that could be used to prevent the hull from rusting, and for each, state the principle by which it works.
🔩 The Rusting Experiment — At a Glance
Tube A
Iron nail + water + air
RUSTS ✅
Tube B
Iron nail + boiled water + oil layer (no O₂)
NO RUST ❌
Tube C
Iron nail + dry air + CaCl₂ (no H₂O)
NO RUST ❌
Conclusion: Iron requires BOTH water AND oxygen to rust. Remove either → no rusting.
⚠️ Top 3 Examiner Traps
- 1.Writing 'iron oxide' instead of 'hydrated iron(III) oxide' — loses the mark every time.
- 2.Saying 'copper rusted' — only iron and steel RUST. All other metals CORRODE.
- 3.Forgetting that BOTH water AND oxygen are required — one condition alone = no rusting.
Cambridge IGCSE Chemistry 0620 · Topic 9.5 · Rusting & Corrosion · Core + Supplement
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