A combination of sand, salt and water is an example of a heterogeneous mixture. A heterogeneous mixture is a type of combination where the constituents of the mixture are not uniform, and there are two or more distinctive phases of separation.
If the two solutes, such as salt and sand, are simultaneously mixed with a solvent, such as water, then the result is a heterogeneous mixture. However, a mixture of salt and water forms a homogeneous mixture, a type of mixture in which the compositions are uniformly distributed throughout the mixture forming only one phase.
Salt completely dissolves in water and can neither be seen nor separated by physical methods. When a mixture, such as a solution of water and salt, is mixed with sand, it gives rise to a heterogeneous mixture consisting of two phases. Sand can be seen at the bottom of the container, while the solution of salt and water fills the top of the mixture. This mixture can be easily separated by pouring off the salty water into another container, leaving the sand behind. To recover the salt from the mixture, the solution is boiled until all of the water is evaporated, which leaves the salt remaining.
The difference between homogeneous and heterogeneous mixtures is the extent at which the constituents are mixed together, as well as the uniformity of their combination. Examples of homogeneous mixtures include air, steel, sugar water and vinegar. Heterogeneous mixtures include ice in soda, soil, cereal in milk, mixed nuts and vegetable soup.