Question detail
A student is testing pure substance. Which choice keeps the observation and conclusion correctly linked?
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. It contains multiple types of atoms
- B. It has a uniform and definite composition
- C. It can be separated into its components easily
- D. It is always a liquid at room temperature
Answer
The correct answer is It has a uniform and definite composition. 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 It has a uniform and definite composition. The important distinction is that pure substance must be identified from single element or compound / fixed melting point; answers that swap in a different test or result do not match Pure substances. Other options are weaker when they confuse gas tests, flame colours, ion-test precipitates, chromatography evidence, or pure-substance/formulation wording.
Common mistake
Confusing Boiling Points
Students often think that a substance can be identified as pure if it boils at any temperature within a range.
Remind students that a pure substance has a specific boiling point, and deviations from this indicate impurities.
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