översubkylning

Översubkylning is a phenomenon where a liquid is cooled below its freezing point without becoming solid. This state, known as metastable, is unstable. The liquid remains in its liquid form because the formation of ice crystals, which requires nucleation sites, does not occur. Nucleation can be triggered by mechanical shock, agitation, or the introduction of impurities, causing rapid crystallization.

This process is common with pure liquids. For instance, distilled water can be overcooled significantly below 0°C. In nature, overcooling plays a role in the formation of hail and in atmospheric processes involving clouds. The extent to which a liquid can be overcooled depends on its purity and the presence of nucleation sites. In industrial applications, overcooling can be utilized in refrigeration and food processing to achieve rapid cooling. The transition from an overcooled state to a solid can be quite dramatic and rapid once nucleation is initiated.