A solution can be one of either gases or liquids. A solution is simply a mixture of a solute and a solvent. A solute is matter that is dissolvable. A solvent is the gas or liquid in which the solute dissolves. There are three types of solutions: unsaturated, saturated, and supersaturated. Below is a look at each of these solutions and their differences.

Definitions

• An unsaturated solution is one in which a little amount of solute has been added to the solvent. The solvent absorbs all the solute and still has room for more. The solvent has not reached its limit and can still dissolve more solute if added to it. For example, if you add a spoon of sugar to a glass full of water, the sugar dissolves completely. The solution is unsaturated.
• A solution is said to be saturated when a solute is not able to dissolve in the solvent. As more and more solute is added to the solvent, it gets to a point where the solvent cannot dissolve any more solute because of some particular conditions (note, the ability of solute to dissolve various amounts of solvent varies and depends on the conditions like temperature, pressure etc). This is when the solution becomes saturated. If you add any more solute, it settles at the bottom of the container. For instance, when water is mixed with lemonade crystals, the lemonade crystals dissolve. At the point when no more lemonade crystals can dissolve in the water, the solution is said to be saturated. Any additional lemonade crystals will not dissolve but settle at the bottom because the water is already holding as much as it possibly can.
• A supersaturated solution, on the other hand, is when the excess of solute is dissolved in the solvent as a result of changes in temperature, pressure or other conditions. At room temperature, a saturated solution keeps the maximum possible amount of solute, and the rest becomes excess. If any more solute is added to the solvent, it will not dissolve but rather settle at the bottom of the container. However, if temperatures are increased, the solvent can dissolve additional solute that was initially settled at the bottom. Even if the solution is then cooled down to room temperature, it still can hold this excess of solute dissolved for some time. This is exactly when it becomes supersaturated. But it’s a temporary condition; eventually the excess of solvent will precipitate and the solution will become saturated again.

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Here is an example to illustrate the difference between unsaturated, saturated and supersaturated solutions.

Let’s say that a glass of water can dissolve 10 spoonfuls of sugar at room temperature.

1. Case one: if you add 2 spoons of sugar to a glass of water at room temperature, it will all dissolve, making an unsaturated solution.
2. Case two: if you add 12 spoons of sugar to the glass of water at room temperature, it will dissolve only 10 of them and the two extra spoons will settle at the bottom of the glass. This makes a saturated solution.
3. Case three: if you heat the solution in case two, all the 12 spoons of sugar will dissolve in the solution. Then you can cool it down back to room temperature and see that this amount of water keeps 12 spoons of sugar dissolved, while you know that only 10 spoons can be kept. This makes a supersaturated solution. After a while the excess 2 spoons will precipitate and the solution will come back to a supersaturated state.

Comparison chart

Saturated vs unsaturated vs supersaturated solutions: