Q1. [5] deep thorough-understanding
Both rusting of iron and rancidity of food are caused by oxidation, yet we use very different methods to slow them down — painting iron surfaces versus adding antioxidants or using airtight containers for food. Explain why oxidation is harmful in each case and analyse how each preventive method tackles the root cause of the problem.
Generated by claude-sonnet-4-6 · 2026-06-26 00:55 · grounding rag
Model Answer
Oxidation and its harmful effects:
- Rusting of iron: When iron is exposed to moist air, it reacts with oxygen and water to form reddish-brown rust (iron oxide). This damages the metal structurally, causing car bodies, bridges, and iron railings to deteriorate, leading to enormous financial losses every year.
- Rancidity of food: When fats and oils in food are oxidised, they become rancid — their smell and taste change, making food unfit for consumption.
How preventive methods tackle the root cause:
- Painting iron: Rust requires both air (oxygen) and moisture. Painting creates a physical barrier that cuts off contact between iron and moist air, directly eliminating the conditions needed for oxidation.
- Adding antioxidants: These substances preferentially react with oxygen themselves, preventing the fats/oils from getting oxidised and turning rancid.
- Airtight containers / nitrogen flushing: These methods remove or displace oxygen around the food (chips manufacturers flush bags with nitrogen), so oxidation of fats simply cannot occur.
Both strategies share the same logic: deny oxygen access to the substance being protected.
Source: Chapter 1, Section 1.3; Chapter 3, Section 3.5
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Explanation
- Examiners want you to clearly connect why oxidation is harmful in each case (structural damage vs. taste/smell change) and then analyse — not just list — how each prevention method works against the root cause (oxygen + moisture for rusting; oxygen for rancidity).
- The word "analyse" in the question means you must explain the mechanism of protection, not just name the method.
- Mentioning nitrogen flushing shows you've read the passage carefully and earns extra credit.
- Avoid padding; keep points crisp and targeted at marks.