Unsaturated solutions are solutions that contain less solute than the actual amount of solute that the solvent can dissolve. If more solutes can be dissolved in the solution, the solution is still considered unsaturated. Every solute and solvent combination has its limit, and once this limit is reached, the substance is in a state that is called the saturation point.
An example of an unsaturated solution is a teaspoon of sugar in a glass of water. If one adds a teaspoon of sugar to a glass of water, it dissolves, and one can still add more sugar to it because it is still unsaturated. However, at some point, the sugar no longer dissolves in the water because the substance is saturated. In other words, the solution has reached its saturation limit. The same process holds with salt and water, a small amount of salt in a large bucket of water dissolves, and the water is considered an unsaturated solution. Iced tea and coffee can also be considered examples of unsaturated solutions. There are different solubility rules to consider in determining how much of a solute can be dissolved in a given amount of solvent, but as long as the solvent can dissolve more of the solute being added, it is still considered an unsaturated solution.