Question

If a solution of a certain salt in water is saturated at some temperature and a few crystals of the salt are added to the solution, what happens? What happens if the same quantity of the same salt crystals is added to an unsaturated solution of the salt?

Short answer

In a saturated solution, added salt doesn't dissolve; in an unsaturated solution, it dissolves until saturation.

Step-by-step solution

Define Saturated Solution

A solution is saturated when it cannot dissolve any more solute at a given temperature. This means it has reached its maximum concentration of dissolved solute.

Observing Additional Crystals in Saturated Solution

When a few crystals of the salt are added to a saturated solution, the added salt will not dissolve. This is because the solution is already holding as much dissolved salt as it can at that temperature.

Define Unsaturated Solution

A solution is unsaturated if it contains less solute than it can potentially dissolve at a given temperature. This means it has not reached its maximum capacity for dissolving the solute.

Observing Additional Crystals in Unsaturated Solution

When the same amount of salt is added to an unsaturated solution, the salt crystals will dissolve until the solution becomes saturated. If there's more solute than needed to saturate the solution, the excess will remain as solid crystals.

Key concepts

Saturated Solution

A saturated solution is a mixture in which no more solute can be dissolved in the solvent at a specific temperature. It has reached a maximum solute concentration, which means it's at its capacity for holding dissolved particles.
If you add more solid solute into a saturated solution, it will not dissolve. Instead, the additional crystals will remain solid in the solution. This is because the dissolved solute already occupies all available spaces in the solvent.
This can be visualized by imagining a sponge completely soaked with water. Any more water poured onto the saturated sponge will simply run off instead of being absorbed. Similarly, a saturated solution cannot absorb any more solute under the given conditions.

Unsaturated Solution

An unsaturated solution refers to a mixture that still has room to dissolve more solute at a given temperature. It means that the solution's solute concentration is below its maximum solubility point.
In an unsaturated solution, if additional solute (like salt crystals) is added, it will continue to dissolve until it reaches a saturation point. This dissolution occurs because the solution has not yet utilized all the available spaces for dissolved particles.
Think of an unsaturated solution as a sponge that hasn't soaked up enough water. When you add a bit more water, the sponge can still absorb it. Similarly, the solution can still take in more solute without any excess left undissolved.

Solute Concentration

Solute concentration is the measure of how much solute is present in a given quantity of solvent. It is usually expressed in terms of moles per liter (molarity) or grams per liter.
In a saturated solution, the solute concentration is at its maximum for a specific temperature. If you try to add more solute, it remains undissolved because the concentration limit has been reached.

• High solute concentration: Occurs in a saturated solution.
• Low solute concentration: Found in an unsaturated solution.

Temperature plays a crucial role because solubility can change with temperature variations. Most solutes dissolve more in warmer solvents, meaning the saturation point depends on how hot or cold the solvent is.
By understanding solute concentration, you can predict how much more solute a solution can handle before becoming saturated or oversaturated, helping in practical applications like cooking or chemical reactions.