What distinguishes a heterogeneous mixture?

A heterogeneous mixture is characterized by having distinct and separate phases, which means that the different components of the mixture can often be seen and are not uniform in composition. This means that if you were to look at a sample of a heterogeneous mixture, you would be able to identify different regions where different substances are present, such as oil and water separating, or a salad where the lettuce, tomatoes, and cucumbers can all be distinguished.

The other attributes do not define a heterogeneous mixture: uniform composition refers to a homogeneous mixture, where the components are evenly distributed and not visually distinguishable. The presence of dissolved substances typically describes a solution, which is also a form of homogeneous mixture. Low visibility of components could apply to both homogeneous and heterogeneous mixtures depending on the context, but it does not specifically characterize heterogeneous mixtures, where the components are often clearly visible and distinct.