The question is an application to my lessons: during melting the temp remains constant, during solidification the temp remains constant. But sometimes a liquid can ‘forget’ to solidify and cools down further and thus remains liquid below the solidification point. We also have this phenomenon with water, rain… hypothermic rain. What conditions (pressure, temp, cooling speed,…??..) do you have to have so that water high above our heads does not freeze but still goes below 0°C?
Regards, Jan Vandorpe, physics teacher
Answer
Water becomes ice when the kinetic energy (temperature) of the particles can no longer exceed the force of attraction between the particles.
The ice formation starts in places where the attraction between the particles is already strong, in other words in places where there is already a small ice crystal or other impurity. A supercooled liquid is an unstable condition that can be reversed by, for example, applying impurities or a shock. The reverse (overheating) can also occur.
http://polymer.bu.edu/hes/articles/ms98.pdf
The attached videos show a supercooled gel, which starts to solidify with a shock (caused by a clicking plate). In the infrared image you can see the latent heat that is released during solidification.
Answered by
Professor Walter Lauriks
Physics Acoustics
Old Market 13 3000 Leuven
https://www.kuleuven.be/
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