What defines a solution?

A solution is defined as a homogeneous mixture composed of two or more substances that exist in a single phase. This is distinct from other types of mixtures, where the components may not be uniformly distributed or may exist in multiple phases. In a solution, the solute (the substance being dissolved) is evenly distributed within the solvent (the substance doing the dissolving), resulting in a uniform composition throughout.

For instance, when salt is dissolved in water, the individual salt ions disperse evenly throughout the water, creating a homogeneous solution. The characteristics that make a solution homogenous include the fact that the components cannot be easily separated by physical means, and they do not settle out over time as is seen in suspensions or colloids.

The correct identification of a solution as a homogeneous mixture is crucial, as it sets the foundation for understanding various properties and behaviors of solutions in chemistry, such as concentration, solubility, and colligative properties.