October 31 seems like an appropriate place to begin my CHEM
musings, so welcome to Hufflepuff Hippo’s Halloween inaugural blog post!
Since this is my first day blogging, it seems appropriate to
muse about what I do in the first day of my introductory chemistry courses.
What is the scale of chemistry? By this I mean: Where does the action take
place? It turns out to be at the level of atoms and molecules, and as a chemist I would like my students to
embrace the concept of the atom. Actually all of them come into class having
already embraced the notion that the atom is the building block of matter. (The
first question I pose is “What is matter and why does it matter?”) What I want
them to learn, as part of teaching scientific inquiry, is how strange a notion
it is to think that all matter is made up of indivisible particles that are too
small for us to see and touch.
For the past ten years or so I have typically illustrated
the idea by holding up my one-page syllabus and asking the question: “What do I
have in my hand?” (I usually have to preface this by asking them to humor me and shout out
answers to my seemingly silly questions.) I get answers ranging from paper,
syllabus, ink on paper, part of a tree, and so on. Then I tear the paper in
half and pose the question again. Then I tear off a small but clearly visible
piece of paper and pose the question again. (Some years a student will shout
out “confetti”!) Finally I enact tearing what might be a very tiny piece of
paper but no one can actually see if I have torn off anything. “Could it be
nothing?” I ask.
James Clerk Maxwell, in a wonderful paper titled “Molecules”
that appeared in the esteemed journal Science in 1873, discusses this same idea.
Can a drop of water be infinitely subdivided? Is there a point at which it
ceases to be “water”? (It’s particularly interesting that at the time there was
still much debate as to whether molecules existed, but more on that in a
subsequent post.)
In class, we then pretend to be ancient Greeks and consider whether
the fundamental building block of matter should be the atom, water (as
suggested by Thales) or the four elements as championed by Aristotle, by
debating the pros and cons of each idea. Since Aristotle’s idea won out, I lead
the students through a brief history of the alchemists and their quest to make
the philosopher’s stone. (Harry Potter’s first adventure makes a brief cameo
here!) In particular we discuss the approach taken by the alchemists and what
some of their favored substances were that should go into the mix.
I have been thinking about a different approach to this
first class that I might like to try out next year. I am thinking of asking the
students to discuss what Potion they might want to concoct, and what
ingredients they think should go into such a potion. To gauge how this might
go, I wrote a “no credit” question at the end of an exam I gave today. (Yes, I
gave an exam in my chemistry class today. No, I did not realize it was
Halloween when I set the exam date before the semester started. I guess I’m a
Muggle of the most clueless sort.) The question goes something like: “If you are a Muggle, what
Potion would you want to learn how to make?” I’m curious to see what the
responses are, and when I have finished grading, I will discuss the range of
responses in a subsequent post.
Happy Halloween!
