Supersaturated Solution
Definition and meaning of Supersaturated Solution in chemistry.
Supersaturated solution refers to a solution containing more dissolved solute than would normally be stable at a given temperature and pressure. It represents a metastable state that persists until disturbed.
In more detail
Supersaturation typically occurs when a saturated solution is cooled carefully without mechanical disturbance, preventing the excess solute from crystallizing out. Although the solution contains more solute than the saturation point allows, crystallization does not occur spontaneously because it requires nucleation energy. Any disturbance, such as scratching the container, adding a seed crystal, or vibration, can trigger rapid crystallization as the system shifts toward equilibrium. This instability makes supersaturated solutions useful in classroom demonstrations and commercial applications like reusable heat packs.
Key facts
| Field | Physical Chemistry |
|---|---|
| Common example formula | CH3COONa (sodium acetate) |
| State | Metastable liquid with excess dissolved solute |
| Triggered by | Nucleation (seed crystal, vibration, dust particles, or scratching) |
When a solution of sodium acetate is boiled and cooled carefully without stirring, it can remain liquid below its normal crystallization temperature, forming a supersaturated solution. Adding a seed crystal or scratching the beaker causes rapid crystallization and a significant heat release (exothermic process).
Frequently asked questions
How is a supersaturated solution different from a saturated solution?
A saturated solution contains the maximum amount of dissolved solute at equilibrium. A supersaturated solution contains more solute than is thermodynamically stable, making it prone to sudden crystallization when disturbed.
Why doesn't crystallization happen immediately in a supersaturated solution?
Crystallization requires nucleation energy to initiate crystal growth. Without a nucleation site such as a seed crystal or dust particle, the system can remain metastably liquid even though crystallization is energetically favorable.