Question detail
Which answer avoids confusing pure substance with another qualitative analysis result?
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
Purity, formulations and chromatography
Question
- A. They can melt and boil at a range of temperatures
- B. They melt and boil at specific temperatures
- C. They do not have a melting or boiling point
- D. They can be mixtures of different substances
Answer
The correct answer is They melt and boil at specific temperatures. It matches pure substance because the evidence is single element or compound / fixed melting point and the expected result is purity evidence.
Explanation
The correct option is They melt and boil at specific temperatures. Use this as an exam check: if the observation is not purity evidence, the conclusion about pure substance is not properly supported. Other options are weaker when they confuse gas tests, flame colours, ion-test precipitates, chromatography evidence, or pure-substance/formulation wording.
Common mistake
Misunderstanding Melting and Boiling Points
Students often think that all substances melt and boil at the same temperature regardless of purity.
Remember that a pure element or compound has specific melting and boiling points, while impurities can alter these temperatures.
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