Explain how you would use boiling point data to determine if a liquid is a pure substance or a mixture.

A high-scoring answer should explain interpret melting point or boiling point data to decide whether a substance is pure or impure. Use evidence before identification: name the relevant test or measurement, state the observation, and then connect the result to Pure substances.

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. A complete answer should use the approved objective wording, include the relevant evidence, and avoid unsupported identification claims.