Mixtures and Solutions

A mixture is formed when two or more substances are combined without undergoing a chemical reaction. Each substance keeps its own chemical identity and can usually be separated by physical methods such as filtration, evaporation, distillation or magnetic separation. Mixtures can be homogeneous, meaning their composition is uniform throughout, or heterogeneous, meaning different parts can be distinguished.

A solution is a type of homogeneous mixture in which one substance, called the solute, is evenly dissolved in another substance, called the solvent. Salt water and sugar dissolved in water are familiar examples. Air is also considered a homogeneous mixture because its different gases are evenly mixed under normal conditions.

The amount of solute that dissolves in a solvent depends on factors such as temperature, pressure for gases and the nature of the substances involved. When no more solute can dissolve under given conditions, the solution is said to be saturated. Understanding mixtures and solutions is important in cooking, medicine, environmental science and industry.

Water treatment plants separate unwanted substances from water, pharmacists prepare medicines with carefully controlled concentrations and many foods rely on precise mixtures of ingredients. Scientists also use techniques such as chromatography to separate and identify the components of complex mixtures. Learning how mixtures behave helps explain many everyday processes and allows materials to be selected or prepared for specific purposes.