Question

You are given a liquid. Briefly describe steps you would take to show whether it is a pure substance or a homogeneous mixture.

Short answer

Four steps can be taken to determine whether a liquid is a pure substance or a homogeneous mixture: visual inspection, boiling point test, distillation, and chromatography. If the liquid is homogeneous with a fixed boiling point and cannot be distilled or separated into different components, it is a pure substance; otherwise, it is a mixture.

Step-by-step solution

Visual Inspection

Visually inspect the liquid. Pure substances are often clear and homogeneous mixtures are generally uniform in appearance, but some mixtures can have visible components. If it is a colored liquid or there are visible substances in the liquid, it might indicate that it's a mixture.

Conduct a Boiling Point Test

Perform a boiling point test. Pure substances have a fixed boiling point. If the liquid boils at a specific temperature and not over a range of temperatures, it might indicate that it is a pure substance.

Distillation

Carry out a process of distillation. Distillation exploits the different boiling points of the components in the mixture. If after distillation there are separate components left, then the substances were in a mixture.

Chromatography

Undertake a chromatography test if distillation didn't provide a definitive answer. Chromatography separates a mixture into its individual components. If multiple substances emerge, the original material was a mixture.