How is a solution defined in chemistry?

A solution in chemistry is defined as a homogeneous mixture of two or more substances. This means that the components of the solution are uniformly distributed at the molecular level and cannot be distinguished from one another visually. In a solution, one substance, the solvent, is present in greater amount and is responsible for dissolving the other substances, known as solutes.

For example, when table salt is dissolved in water, the salt (solute) mixes thoroughly with the water (solvent), resulting in a clear and uniform solution. This uniformity is a key characteristic of solutions, contrasting with heterogeneous mixtures where the different components can usually be seen and can settle out over time.

In other choices, a heterogeneous mixture refers to combinations like oil and water, where distinct components remain separate and visible. A combination of solids only does not encompass the definitions applicable to solutions, as solutions can include liquids and gases as well, not just solids. A chemical reaction in liquid form does not accurately define a solution, as a solution does not involve a change in chemical composition; instead, it involves the process of solvation where solutes are simply dispersed within a solvent without forming new substances.