Principle

In general fluids, gases und solids expand when heated. Water
though has a special property, which lets it stand out from most
other fluids: Its density reaches its maximum at 4 °C. Below and
above 4 °C the density decreases. Therefor ice is lighter than
water and swims at the surface.

In this experiment the anomaly of water shall be demonstrated in
an ice bath with two thermometers.