Using Peltier cell to study solid-liquid-vapour transitions and supercooling

We propose an apparatus for teaching experimental thermodynamics in
undergraduate introductory courses, using thermoelectric modules and a
real-time data acquisition system. The device may be made at low cost,
still providing an easy approach to the investigation of liquid–solid and
liquid–vapour phase transitions and of metastable states (supercooling). The
thermoelectric module (a technological evolution of the thermocouple) is by
itself an interesting subject that offers a clear example of both thermo-electric
(Seebeck effect) and electro-thermal (Peltier effect) energy transformation.
We report here some cooling/heating measurements for several liquids and
mixtures, including water, salt/water, ethanol/water and sodium acetate,
showing how to evaluate the phenomena of freezing point depression and
elevation, and how to evaluate the water latent heat.