Alijäähtyminen

Alijäähtyminen, also known as supercooling, is a phenomenon where a liquid is cooled below its freezing point without solidifying. This state is metastable, meaning the liquid is unstable and can transition to a solid state if disturbed. The absence of nucleation sites, such as impurities or rough surfaces, is crucial for preventing crystallization in a supercooled liquid.

When a supercooled liquid is agitated or exposed to a seed crystal, it can rapidly solidify. This sudden transition releases latent heat, which can cause the temperature of the liquid to rise back to its freezing point. Alijäähtyminen is observed in various substances, including water, which can be cooled to below 0 degrees Celsius under controlled conditions.

This phenomenon has practical implications in meteorology, where supercooled water droplets in clouds can contribute to the formation of ice crystals and subsequent precipitation like snow or hail. In laboratory settings, alijäähtyminen is utilized in cryopreservation techniques to store biological samples at low temperatures without ice crystal formation, which could damage cellular structures. Understanding the conditions that promote and disrupt alijäähtyminen is important for both scientific research and technological applications.