An unsaturated solution is one where the solvent has not yet reached the maximum amount of solute it can dissolve at a given temperature. This means that more solute can still be added to the solution without forming a precipitate. Here are two examples:
- Saltwater: When you mix table salt (sodium chloride) into water, the water can dissolve a considerable amount of salt. If you add salt gradually, there will come a point where all the salt dissolves easily without any settling at the bottom. As long as the water temperature remains the same, if the solution still allows you to add more salt and it dissolves, it is considered unsaturated.
- Sugar in Tea: If you take a cup of hot tea and add sugar to it, the sugar will dissolve completely. In a hot cup of tea, you can keep adding sugar until it can no longer dissolve (which may take quite a bit), but initially, as long as any sugar you add continues to dissolve, the tea is an unsaturated solution.
In both examples, the key aspect of being unsaturated is that more solute can be added without reaching the limit of what the solvent can dissolve.