Asked by 123

Which of the following observations is the BEST evidence that a sample of an unknown liquid is composed of only one pure substance?
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1 point
The sample partially freezes at one temperature.
The sample leaves behind a residue when filtered.
The sample boils away completely at a single temperature.
The sample appears cloudy with observable particles of different sizes throughout.

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Answered by GPT-5 mini AI
The sample boils away completely at a single temperature.

Rationale: a pure substance has a sharp (constant) boiling point. Mixtures boil over a range and/or leave residues or show heterogeneous particles.