<P> In chemistry, a mixture is a material made up of two or more different substances which are mixed . A mixture refers to the physical combination of two or more substances in which the identities are retained and are mixed in the form of solutions, suspensions and colloids . </P> <P> Mixtures are one product of mechanically blending or mixing chemical substances such as elements and compounds, without chemical bonding or other chemical change, so that each ingredient substance retains its own chemical properties and makeup . Despite that 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 using physical (mechanical or thermal) means . Azeotropes are one kind of mixture that usually pose considerable difficulties regarding the separation processes required to obtain their constituents (physical or chemical processes or, even a blend of them). </P> <P> Mixtures can be either homogeneous or heterogeneous . A homogeneous mixture is a type of mixture in which the composition is uniform and every part of the solution has the same properties . Examples of homogeneous mixtures include alloys and alcohol in water . A heterogeneous mixture is a type of mixture in which the components can be seen, as there are two or more phases present . </P> <P> One example of a mixture is air . Air is a homogeneous mixture of the gaseous substances nitrogen, oxygen, and smaller amounts of other substances . Salt, sugar, and many other substances dissolve in water to form homogeneous mixtures . A homogeneous mixture in which there is both a solute and solvent present is also a solution . Mixtures can have any amounts of ingredients . </P>

What are the two types of mixtures in science