What is a Mixture?

Mixtures are constituted by more than one kind of pure form of matter, known as a substance. A substance cannot be separated into other kinds of matter by any physical process. We know that dissolved sodium chloride can be separated from water by the physical process of evaporation. However, sodium chloride is itself a substance and cannot be separated by the physical process into its chemical constituents. Similarly, sugar is a substance because it contains only one kind of pure matter and its composition is the same throughout. 

Soft drinks and soil are not single substances. Whatever the source of a substance may be, it will always have the same characteristic properties. 

Therefore, we can say that a mixture contains more than one substance.