Slicing the Chemistry Pi(e)

Prompted by a colleague to ponder the unity and diversity of chemistry, I’ve been imagining Venn diagrams. For some reason, they come in threes.

 

Let’s start by considering the three traditional science disciplines and their mutual overlaps. The following diagram which I’ve previously introduced to introductory students when discussing the definition of life. 

 

I’ve labeled the overlaps from a chemist’s perspective. Physical chemistry is where physics and chemistry overlap (a physicist might call it chemical physics); that’s formally how I’m classified within the world of chemistry. I teach the dreaded P-Chem (Advanced Arithmancy!) and within the American Chemical Society (ACS), I’m part of the PHYS (physical chemistry) division. Biochemistry is where biology and chemistry overlap. And all three might come together in an area I’ve called biophysical chemistry. This way of slicing the chemistry pie visualizes its relationships (and lack thereof in non-overlapping areas) with its sister sciences, physics and biology.

 

The ACS curriculum identifies five areas within chemistry: Analytical, Biochem, Inorganic, Organic, and Physical. To certify that our graduates have gone through the ACS-certified curriculum, our department has to show ACS that our students have covered material in these five areas, usually logged as class hours spent in both lecture and lab across these areas. This classification can be traced historically as chemistry began to specialize into these domains. Nowadays we might also discuss further specialization in areas such as materials chemistry, environmental chemistry, polymer chemistry, nuclear chemistry, solid-state chemistry, or my area of expertise – computational chemistry. You could represent these in a sliced-up pie chart, but I prefer the Venn diagram because it highlights the overlap between boundaries.

 

How might we make sense of all these different subfields and their relationships? Let’s try to group things by category. Here’s one possibility: Geochemistry, Biochemistry, Astrochemistry. These are three distinct areas of chemistry, but they also potentially overlap in interesting ways. You could further subdivide geochemistry into its three spatial realms: lithosphere, hydrosphere, and atmosphere. Once again, the boundary zones are of great interest, chock-full of complexity, and likely to enlarge our understanding of chemistry.

 

When I chat with students about what they might find interesting in chemistry, we discuss what classes they enjoyed, but I also talk to them about two main activities of chemistry: Making and Measuring. While not exclusive to each other, different laboratory activities tend to focus either on one or the other (although we do bring them together at the end). If I was looking for a trinity of chemistry applications, I could perhaps choose: Materials, Medicine, and Manufacturing, for my three Venn circles. Once again, the overlaps might be where interesting action may be found.

 

What unites all these different slices of chemistry? Today I’d say that chemistry focuses on the Molecular level, and translates what’s going on there to the Macroscopic human-sized world where we operate. We’ve used a lot of M-words in the last paragraph, kinda like an M-Theory. All these M-words are anthropocentric to us humans who are practicioners of chemistry.

 

What my colleague actually asked me is whether there are cross-cutting concepts across the different areas of chemistry, or perhaps what unites the slices of the pie. That they’re all pie? Maybe I should ask what are the ingredients of the pie? Or the pi? What does pi have to do with the pie? We’ll get to that.

 

The slices and Venn circles are labeled in ways familiar to chemists. They help us distinguish differences. But what unites them? In the spirit of threes and the anthropocentric “I”, may I suggest the following three concepts: Identity, Interaction, Information. There, I made a Venn diagram!

 

I chose not to use the more familiar structure-function dyad, because I think it’s too limiting, and we’re too used to the mantra that structure dictates function. This limitation is especially apparent in the growing field of Systems chemistry. I haven’t fleshed out my three I’s, but here’s what I can say broadly or vaguely. I think a truly cross-cutting concept should be more generic, and may manifest itself in potentially different but related forms across the different slices of the chemistry pie. (1) While Identity is most easily associated with individual molecular structure, it might encompass more abstract concepts such as familial relationships, classification, and macroscopic views of matter. (2) Interaction isn’t just about intermolecular forces and chemical reactions, and should not just be subsumed into Identity, but may encompass other types of dynamics that chemists are not used to contemplating. (3) Information, the slipperiest of the three, should not just be relegated to cheminformatics or Shannon entropy; I haven’t yet grasped how to think about it in a broader sense beyond the analogy that semantics, and not just syntax, is key to the understanding of language. Information could also encompass other I’s such as Imagination or Interpretation, that highlight the Interaction between observer and observed, a boundary that might prove non-trivial.

 

The slices we have made are human conveniences to corral what might be a huge area into more manageable ones. We may specialize and self-identify (or be identified) with certain slices. But we should be continuously aware that by reducing our field of vision – for good reason, to learn some new things! – we also blinker ourselves from the richness of the whole. In a previous post, I quoted Rosen’s description of that funny number pi – yes, the one that shows up in pies, and that we celebrate by eating said pies on Pi Day. Those seemingly thin boundaries along slices of pie, might actually be broad rich areas of investigation, fractal-like as you look closer, but more complexly so, and certainly not captured by simple Venn diagrams.

 

Identity, Interaction, Information. Perhaps that’s one way to think about the Chemistry Pi.

 

P.S. For other Pi-related posts, see Abstraction or Happy Pi Day!