Eduard-Job-Stiftung für Thermo- und Stoffdynamik

Entropieerzeugung in einem Entropiestrom

The Ice-Water Calorimeter

If entropy is added to an equilibrium mixture of ice and water, the additional entropy causes some ice to melt. This effect is used to measure entropy. The measurement is reversible, since the ice-water calorimeter does not change its temperature during the entropy transfer, and no surplus entropy obscures therefore the measured value.

The entropy of fusion SS of ice can be calculated from the heat of fusion HS(333.55 J/g [1]).

Ice Ih has at its melting point TS = 273.15 K) a lower density = 0.917899 g/cm3 than water = 0.999886 g/cm3 hat [2]. The flow of entropy into the calorimeter causes some ice to melt and decreases so the volume of the ice-water mixture.

The replacement of m (the mass of molten ice) by the definition of the entropy of fusion SS = S/m reveals a linear dependency of on S.

Finally, is replaced by the formula for the volume of a cylinder = to translate the volume change into the water level in the capillary h.

 

The resolution of the ice-water calorimeter is therefore inverse proportional to the square of the capillary radius r2.

  1. David R. Lide, Handbook of Chemistry and Physics, 72nd edition, CRC Press, 1991, Boca Raton
  2. Matthias Schöninger & Jörg Dietrich, HydroScript 2.7, Stand 20.04.2001http://www.hydroskript.de/html/hykp0301.html