Q1. [3] deep thorough-understanding
An alloy of copper and zinc does not conduct electricity as well as pure copper, even though both copper and zinc are good conductors individually.
(i) What general rule about alloys does this observation illustrate?
(ii) Despite being a good conductor of heat, copper is alloyed with zinc to make brass for many household items instead of being used as pure copper. State one advantage of using brass over pure copper for such applications.
Generated by claude-sonnet-4-6 · 2026-06-26 01:07 · grounding rag
Model Answer
(i) This observation illustrates that alloys generally have lower electrical (and thermal) conductivity than their pure parent metals. The irregular arrangement of different atoms in an alloy disrupts the free flow of electrons, thereby reducing conductivity.
(ii) One advantage of using brass (copper-zinc alloy) over pure copper for household items is that brass is harder and stronger than pure copper, making it more durable and resistant to wear and deformation in everyday use.
Source: Metals and Non-metals, Chapter 3 (alloy definition and properties)
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Explanation
- Part (i) is worth ~1 mark: state the rule clearly — alloys have lower conductivity than pure constituent metals. Mention why briefly (disruption of electron flow) if you want to secure the mark fully.
- Part (ii) is worth ~2 marks: the key advantage examiners expect is greater hardness/strength/durability. Avoid repeating conductivity (that's the disadvantage given in the question). The textbook notes alloys are made to improve mechanical properties like hardness.
- Keep answers concise; one clear sentence per part is sufficient for the marks allocated.