The Third Law of Thermodynamics

How close can we get to absolute zero?

The third law of thermodynamics states that there is an abslute entropy scale. The zero of entropy is at absolute zero of temperature on the absolute scale. However, a substance can only have zero entropy if it is a perfrect crystal. Any imperfections lead to a residual entropy. In this section we discuss how to define a perfect crystal and how to use the absolute entropy. The experimental test for these ideas depends on our ability to conduct experiments at low temperatures approaching T = 0 K. However, as the temperature approaches zero the heat capacity also approaches zero.


Calculation of absolute entropy