Take a glass of water and throw in a handful of sand or dirt. Stir it and stir it and stir it. The water may become turbid, or unclear. Have you made a solution? Sand and dirt do not dissolve in water and though it may look homogeneous for a few moments, the sand or dirt gradually sinks to the bottom of the glass.
A suspension is a heterogeneous mixture in which some of the particles settle out of the mixture upon standing. The particles in a suspension are far larger than those of a solution and thus gravity is able to pull them down out of the dispersion medium (water). The typical diameter for the dispersed particles (the sand) of a suspension is about 1000 times greater than those of a solution (less than approximately two nanometers for particles in solution, compared to greater than 1000 nanometers for particles in suspension). Unlike in a solution, the dispersed particles can be separated from the dispersion medium by filtering. Suspensions are heterogeneous because at least two different substances in the mixture can be identified.
- Suspensions are heterogeneous mixtures.
- Some of the material in a suspension will settle out on standing.
- Solid material in a suspension can be removed by filtration.