Long answer·Standard multi-step (3/5)·No calculator
Difficulty guide
The label describes the problem, not your ability.
1/5 - Foundational
Warm-up setup; checks one basic idea.
2/5 - Routine exam skill
Normal syllabus skill; usually one main rule or interpretation.
3/5 - Standard multi-step
Exam-style problem with multiple steps or a common trap.
4/5 - Hard exam skill
High-end exam problem; combines methods carefully.
5/5 - Challenge
Stretch problem beyond normal exam pressure.
Question
A sample is made by mixing iron filings, sulphur powder, and common salt. Water is added and the mixture is filtered.
Total: 5 marks
(a) State whether the original sample is homogeneous or heterogeneous. (1 mark)
(b) Which component dissolves in water? (1 mark)
(c) Name one physical method to separate iron filings before adding water. (1 mark)
(d) Explain why no new compound is necessarily formed by mixing. (2 marks)
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