Physical and Theoretical Chemistry

Energy Is Everything

What is the third law of thermodynamics?

The most common statement of the third law of thermodynamics is that the entropy of a perfectly crystalline system approaches zero as the temperature of the system approaches zero. (Recall from “Macroscopic Properties: The World We See” that a perfect crystal is a regularly ordered lattice of atoms that exist in a repeating pattern in three dimensions with no defects or irregularities in the lattice.) This is equivalent to saying that a perfectly crystalline system has only one accessible state as the temperature approaches zero. In truth, this isn’t always strictly true since there can be multiple low-energy states that all have the similar energy, but let’s ignore this for now.


This is a web preview of the "The Handy Chemistry Answer Book" app. Many features only work on your mobile device. If you like what you see, we hope you will consider buying. Get the App