A heterogeneous mixture is composed of two or more substances mixed together that does not have a uniform composition. If we removed samples of the mixture from different locations the composition of the two samples would differ.

A heterogeneous mixture contains two different substances in the same or different phases.

Two liquids that do not mix, water and gasoline for example, is an example of a heterogeneous mixture. This example is of two compounds. A heterogeneous mixture might have a liquid and a solid, or a gas and a solid, or two solids. If the components are gases the mixture will not be heterogeneous.