4. Physical Chemistry: The rise of thermodynamics

It may seem easy (specially in hindsight) to find common ground between chemistry and physics. But not so in the late 1800's when that terrain was barely tread. First, you must determine which physics to use, and how it might have something, anything, to say about the chemistry of your system. This is where thermodynamics comes in. It was a relatively new physics at the time. Gibbs gave it root; Ostwald and van't Hoff used it to make physical chemistry a science.  The success of thermodynamics lies in its ability to describe energy transactions between large bodies. These bodies can consist of a single type of atom or molecule like a pure glass of water or, more likely, it can be a mixture. No question that mixing liquids is fun, but the action lies in having them react. The use of thermodynamics to describe chemical reactions gave rise to what may have been the first significant interdisciplinary application of physics to chemistry. Thus the field of physical chemistry was born.

The power of thermodynamics to describe chemical processes—like reactions and phase transitions—is so great that it still fills much of the material that we teach in general chemistry courses. It's useful to understand that atoms and molecules exist as indivisible objects—up to chemical bonds—which allows us to create balanced reactions that also reflect energy transactions. So what need does a chemist have for any other physics? Sadly, the American Chemical Society (ACS) Journal of Physical Chemistry (founded in 1896) and their editor—Wilder Bancroft—answered this question in the negative well beyond the 1920's. Lest you think that Bancroft was a heretic, it is important to note that he was a graduate student of Ostwald and a postdoc of van't Hoff! Under Bancroft's rule, the Journal defined physical chemistry as only that science which involved the use of thermodynamics to understand chemistry. Pretty powerful, yes, but also limited.


(This is the fourth post in a series starting with the first one on interdisciplinary sciences.
Click here for the previous post.)