In chemistry, a mixture is when two or more different substances are mixed together but not combined chemically. The molecules of two or more different substances are mixed in the form of mechanical mixtures, solutions, suspensions, and colloids. While there are no chemical changes to its constituents, the physical properties of a mixture, such as its melting point, may differ from those of the components. Some mixtures can be separated into their components by mechanical means. Azeotropes can not, at least not directly.