What defines a homogeneous mixture?

A homogeneous mixture is characterized by having a uniform composition throughout, meaning that the individual components are evenly distributed and cannot be easily distinguished from one another. This consistency allows for identical properties in any sample taken from the mixture. For example, a solution of salt in water appears the same throughout, regardless of where it is sampled.

In contrast, mixtures with varying composition are classified as heterogeneous mixtures, where different regions can have different properties. Mixtures of two solids can still be homogeneous if the particles are evenly distributed, but not all solid mixtures are homogeneous. Finally, while some mixtures can be difficult to separate, it isn't a defining property of homogeneous mixtures, as some can be separated through physical processes. Thus, the defining feature of a homogeneous mixture lies in its uniform composition.