A heterogeneous mixture does not have a definite composition. Cereal in milk is an example of a heterogeneous mixture. Soil is another example. Soil has pebbles, plant matter and sand in it. Although you may add one substance to the other, they will stay separate in the mixture. We say that these heterogeneous mixtures are non-uniform, in other words they are not exactly the same throughout.
Definition: Heterogeneous mixture
A heterogeneous mixture is one that consists of two or more substances. It is non-uniform and the different components of the mixture can be seen.
Heterogeneous mixtures can be further subdivided according to whether it is two liquids mixed, a solid and a liquid or a liquid and a gas or even a gas and a solid. These mixtures are given special names which you can see in table below.
Phases of matter
Name of mixture
oil in water
Table: Examples of different heterogeneous mixtures