Q1. [3] deep exam-ready
Four metals P, Q, R and S were tested with cold water, hot water and steam. P reacted vigorously with cold water producing fire; Q reacted only with steam; R did not react with water at all; and S reacted with hot water but not violently. Arrange P, Q, R and S in decreasing order of reactivity. Identify one metal from the activity series that could correspond to each of P, Q and R.
Generated by claude-sonnet-4-6 · 2026-06-26 01:05 · grounding rag
Model Answer
Decreasing order of reactivity: P > S > Q > R
Identification of metals:
- P reacted vigorously with cold water, producing fire → Sodium (Na) (reaction is so violent and exothermic that hydrogen catches fire)
- Q reacted only with steam → Iron (Fe) or Aluminium (Al) (metals like aluminium and iron react only with steam, not cold or hot water)
- R did not react with water at all → Copper (Cu) (metals like copper, silver and gold do not react with water at all)
(S corresponds to Magnesium, which reacts with hot water but not violently.)
Source: Chapter 3, Section 3.2.2
---
Explanation
- The examiner expects the correct order first, then identification with brief justification for each.
- S (hot water only, not violently) = Magnesium — but the question only asks to identify P, Q, R, so mention S briefly or skip if marks are tight.
- For Q, either iron or aluminium is acceptable; iron is the most commonly cited textbook example.
- Always link each metal to its behaviour described in the question to earn full method marks.