* 1 point
Which of the following observations is the BEST evidence that a sample of an unknown liquid is composed of only one pure substance?
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.
The sample boils away completely at a single temperature.
This is the best evidence because it indicates that the liquid is a pure substance with a distinct boiling point, which is characteristic of pure substances.