Scale 7: Heat Packs - a podcast by PSD Channel 10 and Little Shop of Physics

The science of weather can be challenging because large changes can occur with a simple change on the molecular level. Case in point? These heat packs... they are in a liquid state, but have been supercooled. That is, they want to be solid, but don't know how to get there. However, if one tiny little crystal can be formed, all of the other molecules can use that point as a way to become solid. By snapping the metal tab inside of them, we can create a reaction and help the liquid become a solid. (As a fun side note, these are therefore heat packs because the phase change releases the stored energy in the liquid.)

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