Pure Substances and Mixtures

Core concept

Pure substances have fixed physical properties, like a specific melting or boiling point, while mixtures often show a range of melting/boiling points depending on their composition. Mixtures are further classified as homogeneous (uniform composition, like a salt solution) or heterogeneous (non-uniform, like a mixture of oil and water, which visibly separates into layers). This distinction between pure substances and mixtures is fundamental to understanding chemical classification and separation techniques.