Saturated vs Unsaturated Solutions
The term saturation has varied definitions in various branches of Chemistry. While, in Physical Chemistry, the idea of saturation is different from how saturation is viewed in Organic Chemistry. Nevertheless, the word saturation has a Latin origin, and it literally means ‘to fill’. Therefore, the basic idea of saturation is to fill up the total capacity whereas unsaturation means that there’s still some more space left to fill the entire capacity.
What is Saturated Solution?
A solution is made up by dissolving a solute in a solvent. The resulting mixture is what we refer to as a solution. At any given temperature and pressure, there’s a limit to the amount of solute that could be dissolved in a particular solvent for the solute to remain dissolved in the solution phase. This limit is known as the saturation point. In the attempt to dissolve more solute surpassing the saturation point, the excess solute will form a precipitate at the bottom, separating itself into a solid phase. This happens in order to maintain the limit of solutes that the solution could hold at a given temperature and pressure.
Therefore, any solution that has reached its saturation point is known as a ‘saturated solution’. In principle, there can be two types of saturated solutions; fully saturated and nearly saturated. When it is fully saturated, usually we would witness a formed precipitate at the bottom due to the inability of further dissolution of solute in the solvent. Whereas when it is nearly saturated, the solution would hold nearly the exact amount of solutes needed for saturation; hence a little bit of added solute can burst into a little precipitate at the bottom. Therefore, when a solution is nearly saturated, even though we consider it as a saturated solution, we would not witness a precipitate at the bottom. The saturation point of a given amount of solution varies depending on temperature and pressure. The same volume of solvent would be able to hold a greater amount of solute in the solution phase when at a higher temperature. Therefore, higher the temperature, higher the amount of solutes needed for saturation. In contrast, when pressure is increased, saturation is achieved easily.
When dissolving the solute in the solvent, it is important to do so with regular mixing. This is done in order to avoid local super saturation (a small amount of volume of solvent that passes its saturation point). Therefore, the solutes must be evenly spread over the entire volume and should not be dropped down at the same place.
What is Unsaturated Solution?
Unsaturated solutions are solutions that have the capacity of dissolving more solutes in them. These solutions are yet to pass their saturation point hence would never carry a precipitate at the bottom. Unsaturated solutions and nearly saturated solutions, as described above, would look almost similar from the outside, but they can be easily distinguished by performing a fast step. That is, upon the dissolution of a bit of solute molecules, the nearly saturated solution would burst into a precipitation almost instantly passing the saturation point whereas for an unsaturated solution, there would be no difference in appearance as the solutes will fully dissolve since there’s enough room to accommodate them in the solution phase.
Generally, a solution which was saturated at a lower temperature, can be made unsaturated at a higher temperature as the increase in temperature increases the carrying capacity of solutes in the solution phase.
What is the difference between Saturated and Unsaturated Solutions?
• Saturated solutions are unable to dissolve solutes further in the solution phase, whereas unsaturated solutions could.
• Usually, saturated solutions carry a precipitate at the bottom but unsaturated solutions do not.
• With increasing temperature, saturation decreases but unsaturation increases.