Science (086) — AI-generated practice question

Corrosion is the process by which a metal is attacked by substances in its surroundings such as moisture and acids, leading to its deterioration.

Chemical formula of rust: $\text{Fe}_2\text{O}_3 \cdot x\text{H}_2\text{O}$ (hydrated iron oxide)

Conditions required for rusting: Both air (oxygen) and water (moisture) must be present simultaneously. If iron is exposed to only water or only dry air, it does not rust.

Harmful consequence: Corrosion causes severe damage to iron structures such as bridges, railings, car bodies and ships, leading to enormous financial loss every year.

Source: Chapter 1, Section 1.3.1; Chapter 3, Section 3.5

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• Examiners expect the chemical formula of rust — $\text{Fe}_2\text{O}_3 \cdot x\text{H}_2\text{O}$ — to be written correctly. Many students lose marks by omitting it.
• The key experimental finding (Activity 3.14) is that both air and water are needed — state this clearly, not just one condition.
• For the harmful consequence, any one specific example (bridges, ships, etc.) with mention of financial/structural damage is sufficient for 1 mark.