This post was imported from my personal blog, as I make the transition to having a professional blog.
I just gave a class on chemical equilibrium, and one of the big concepts was that although some things don’t look like they’re changing there are probably still a bunch of chemical reactions happening. They just have opposing reactions that balance things out. After a ridiculously fun experiment with some buckets of water, we talked about an example of the first person to suggest chemical equilibrium: Claude Louis Berthollet.
Berthollet, back in 1803, observed sodium carbonate (Na2CO3) on the shore of a lake, and thereafter proposed the world’s first simultaneous back-reaction. The “forward” reaction in question was the well known fact that if you reacted Na2CO3 with CaCl2 in water, they would form CaCO3 solid (limestone) and salt water (NaCl(aq)). Nobody had yet observed chemical reactions to go in the opposite direction like Berthollet just had. Reactions were just thought of as one-way processes. The observation of Na2CO3 on the shore of a (very salty) lake led Berthollet to propose that it came from the combination of CaCO3 and NaCl. So, this begins to form a very new picture of what’s happening in a lake with a bed of limestone. When you or I look at a lake and its bedrock, we see a system that appears static and unchanging. On the molecular level, however, the lake and the limestone are continuously reacting with each-other. There is a constant reaction of limestone dissolving to form calcium cations and carbonate anions, and there is another constant reaction of calcium and carbonate reacting to form limestone. The lake and the limestone, therefore, are not static, unchanging things. They’re interdependent, continuous processes. Which is cool to think about once in a while. Dude.
Now that I’ve had to give a number of teaching talks on different topics, I’ve gotten into a rhythm of including historical information, which turns out to provide a lot of interesting stories and examples. A few years ago, even, this would not have been very feasible unless you had a collection of books on the history of science and a lot of time on your hands. With Wikipedia, though, you can get stories, time lines, drawings, and old photographs in a matter of seconds. And it’s all Creative Commons, so you don’t even have to think twice about the legality of copying an image. That’s what it’s there for! (Though you may technically be required to reference the original work/artist/license in some cases).
