During the burning of metals in air, iron filings burn vigorously when sprinkled into a flame, yet a solid pi…

Question

During the burning of metals in air, iron filings burn vigorously when sprinkled into a flame, yet a solid piece of iron does not burn even on strong heating. What does this tell you about the factor(s) that determine the rate at which a metal reacts with oxygen, beyond just its position in the reactivity series?

Accepted Answer

## Model Answer The rate of reaction of a metal with oxygen depends not only on its reactivity but also on the **surface area** exposed. Iron filings have a very large surface area, allowing vigorous burning, whereas a solid piece of iron has a much smaller surface area, so it does not burn even on strong heating. *Source: Chapter 3, Section 3.2.1* ## Explanation The textbook explicitly states: "Iron does not burn on heating but iron filings burn vigorously when sprinkled in the flame." This points to **surface area** as the key additional factor. Examiners want you to name this factor clearly and link it to the observation given. Do not just repeat reactivity — the question asks what is *beyond* position in the reactivity series.

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