What does it mean if a mixture is described as heterogeneous?

A mixture described as heterogeneous means that it contains visibly different substances. This characteristic is key to understanding how heterogeneous mixtures differ from homogeneous mixtures. In a heterogeneous mixture, the individual components can be seen and distinguished from one another, illustrating that the mixture is not uniform throughout. Examples include a salad, concrete, or a mixture of sand and salt, where individual parts can be perceived distinctly. This visual difference is what defines the mixture as heterogeneous.

The other options do not accurately describe heterogeneous mixtures. Uniform composition is a hallmark of homogeneous mixtures, while the ease of separation applies to many types of mixtures, not solely to heterogeneous ones. A purely chemical nature is irrelevant to this classification, as it doesn’t pertain to mixtures, which can consist of physical combinations of substances and do not have to be purely chemical.