A 200 g piece of iron is placed in a sealed container containing 1 L of water. After 3 days the iron turns reddish‑brown. Explain whether this is a physical or chemical change, and give two other examples of similar changes.
Answer
Chemical change
The correct answer is Chemical change — Two other examples of such changes are burning of wood and decomposition of hydrogen peroxide.
Step-by-step solution
- Rusting involves a reaction between iron, oxygen and water to form iron oxides.
- This reaction changes the composition of iron, not just its appearance.
- Therefore the change is a chemical change.
- Two other examples of such changes are burning of wood and decomposition of hydrogen peroxide.
Common mistake: Assuming rusting is only a colour change
Concept tested: Chemical change indicators
Published · How this solution was prepared and checked
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