A saturated solution is a chemical solution containing the maximum concentration of a solute dissolved in the solvent. The additional solute will not dissolve in a saturated solution.
The amount of solute that can be dissolved in a solvent to form a saturated solution depends on a variety of factors. The most important factors are:
- Temperature: Solubility increases with temperature. For example, you can dissolve much more salt in hot water than in cold water.
- Pressure: Increasing pressure can force more solute into solution. This is commonly used to dissolve gases into liquids.
- Chemical Composition: The nature of the solute and solvent and the presence of other chemicals in a solution affects solubility. For example, you can dissolve much more sugar in water than salt in water. Ethanol and water are completely soluble in each other.
Examples of Saturated Solutions
You encounter saturated solutions in daily life, not just in a chemistry lab. Also, the solvent does not need to be water. Here are some common examples:
- A soda is a saturated solution of carbon dioxide in water. This is why, when the pressure is released, carbon dioxide gas forms bubbles.
- Adding chocolate powder to milk so that it stops dissolving forms a saturated solution.
- Salt can be added to melted butter or oil to the point where the salt grains stop dissolving, forming a saturated solution.
- If you add enough sugar to your coffee or tea, you can form a saturated solution. You'll know you've reached the saturation point when the sugar stops dissolving. Hot tea or coffee allows much more sugar to be dissolved than you can add to a cold beverage.
- Sugar can be added to vinegar to form a saturated solution.
Things That Will Not Form Saturated Solutions
If one substance will not dissolve into another, you cannot form a saturated solution. For example, when you mix salt and pepper, neither dissolves in the other. All you get is a mixture. Mixing oil and water together will not form a saturated solution because one liquid does not dissolve in the other.
How To Make a Saturated Solution
There's more than one way to make a saturated solution. You can prepare it from scratch, saturate an unsaturated solution, or force a supersaturated solution to lose some solute.
- Add solute to a liquid until no more dissolves.
- Evaporate solvent from a solution until it becomes saturated. Once the solution starts to crystallize or precipitate, the solution is saturated.
- Add a seed crystal to a supersaturated solution so extra solute will grow onto the crystal, leaving a saturated solution.
What Is a Supersaturated Solution?
The definition of a supersaturated solution is one which contains more dissolved solute than could ordinarily dissolve into the solvent. A minor disturbance of the solution or introduction of a "seed" or tiny crystal of solute will force crystallization of excess solute. One way supersaturation can occur is by carefully cooling a saturated solution. If there is no nucleation point for crystal formation, the excess solute may remain in solution.