True Names

Schools of magic are now common in the literature world of fantasy, Hogwarts simply being the most famous and widely known. The storylines are familiar – young precocious student who has suffered early loss finds way to magical school where an inborn spark is honed into talent. Protégé, possibly still raw with more to discover, is forced to grow up quickly and embarks on quest – typically to conquer some evil or malevolent force.

 

I don’t know who first came up with this narrative arc, put possibly the writer who brought it to a large swath of readers is Ursula K. Le Guin in the now-classic A Wizard of Earthsea from 1968. I’ve read some of Le Guin’s sci-fi, but had not gotten around to the Earthsea series. I finally read the first book this morning in a single three-hour sitting. It reminded me a little of the Prydain Chronicles beginning with Lloyd Alexander’s The Book of Three from 1964 in terms of story arc and intended audience (younger readers and teenagers). I can see where A Wizard of Earthsea borrowed ideas from Tolkien’s world where dragons are concerned, but mostly I see where others have borrowed from it.

 

The magic system is sympathetically tied to the natural world, as elaborated and expanded upon in the more contemporary and grittier The Name of the Wind by Patrick Rothfuss. The power of magic comes from knowing the true names of entities. These true names are hidden in an ancient mostly forgotten language. Incantations have power because by truly naming something, you have power over it. The lite version of this can be found in occasional Latin-ish spells in the world of Hogwarts, although I don’t think as much thought was put to tie those incantations into a self-consistent system. Tolkien, a master of words and languages, doesn’t take this route and the magic of Middle Earth is much subtler.

 

In Earthsea, as in many other fantasy novels, arcane knowledge is key to magic. It’s not easy to learn this on your own, and that’s why a school of magic is needed. Teachers who themselves study and practice the magical arts are key to the whole endeavor. In these magical worlds, education is key. In our world, where science and technology are magic’s counterparts, perhaps the same holds true. Cutting-edge science is not so easy to learn on your own even with Internet access, and good teachers are key. Perhaps my job as a teacher of chemistry will hold out for a while against the A.I. bots who may one day replace me.

 

Earthsea’s magic is closely tied to the natural world: physical, chemical, biological. To manipulate the elements requires a close knowledge of them. Much of elementary magic begins in casting illusions – things that seem real, but lack substance. More powerful magic allows for true transformation, but potentially upsets the equilibrium of the natural world with far-reaching consequences. The use and manipulation of energy is emphasized as a cost in performing magic, sometimes with tragic results. But at its heart, magic relies on the abstract knowledge of true names, akin to glimpsing the invisible Forms of Plato behind their physical and visible substantiations. Knowledge is power. Maybe.

 

I’ve said little of the journey of the young protagonist wizard in the first Earthsea novel so as not to spoil the story. Growing up, maturing, learning some things the hard way, are key themes of any young adult novel. Strip away the magical elements, and the best stories are those about personal human struggles, and the hard choices of right, wrong, and plenty of grey all around. That journey is perhaps growing into one’s true name, not the one given to you at birth, but the person you are becoming. It is perhaps a deeper, older, magic, one that Aslan the Lion knew about, that a power-hungry White Witch failed to comprehend; or something that Dumbledore understood that Voldemort disdained.

The Magical Mind

Hurrah, my semester is done! I have a bunch of books lined up for my holiday reading. First up, a series of articles compiled as Imagining the Impossible: Magical, Scientific, and Religious Thinking in Children, edited by Rosengren, Johnson & Harris (Cambridge University Press, 2000). Yes, they’re academic articles and this isn’t light reading. I was hoping to learn more about how children approach fantastic thinking through fantasy stories. There’s a little of it, but not as much as I anticipated, so I was a little disappointed. But the readings were still interesting overall.

 

The opening chapter, “The Makings of the Magical Mind” was my favourite. The authors provide a point-by-point working definition of magic, which they summarize as: “Magic is a cognitive intuition or belief in the existence of imperceptible forces or essences that transcend the usual boundary between the mental/symbolic and physical/material realities, in a way that (1) diverges from the received wisdom of the technocratic elite, (2) serves important functions, and (3) follows the principles of similarity and contagion.”

 

They focus on sympathetic magic, of which one principle is that if two things resemble one another (“like produces like”) in some way, shape, or form, they have a deeper connection going beyond what we consider as science can explain. Voodoo is one example. Another, more mundane, is our common disgust at the thought of touching fake poop. This also illustrates the principle of contagion whereby some essence can be transferred through physical contact – you might be “contaminated” by the essence-of-poop, whatever that is. The authors provide many examples from a variety of cultures around the world for this seemingly magical way of thinking. After reading the chapter, I started to notice my own magical ways of thinking in ordinary daily life, where I mistake correlation for causation.

 

Chapter 4, “Development of Beliefs About Direct Mental-Physical Causality” usefully categorizes physical and mental cause-effect relationships in the context of whether an action takes place within an individual versus between individuals. For example, if you push someone, this is a physical change acting between individuals. This is normal cause and effect, and no one would be surprised. However, if you willed someone else to fall by pushing them purely with your mind (and your mark could not see you or be physically distracted or influenced by you in any way), this would seem magical. This telekinetic ability represents “action-at-a-distance”, something that seemed magical when Newton’s Law of gravitation was first proposed; scientists readily accept the latter, but not the former.

 

In this blog, I have speculated that magic in the Hogwarts world relies on electromagnetic radiation as a “carrier”, possibly in the same way that photonic particle exchange mediate the action-at-a-distance in Coulomb’s Law of electrostatics – which you’ve likely encountered as “like charges repel” and “opposite charges attract”. These sound uncannily like sympathetic magical principles. Perhaps that’s because I’m still thinking like a scientist, trying to ground the underlying principles of magic, somewhere in the physical principles of the energy-matter continuum. The magical mind should perhaps dismiss such efforts and proclaim that magic is truly action-at-a-distance in a mind-over-matter way. Maybe my attempts are all for naught.

 

The articles in this compendium do feature a number of interesting “experiments” and interviews with children, adolescents, and adults. They explore wishful thinking, imaginary friends, believing in Santa, praying to God, and more. Children are neither scientists-in-the-making as they explore the world around them or purely magical thinkers easily influenced and led astray. Growing into adulthood does not shed all forms of magical thinking, and we continually display approaches that can be classified as “folk-biology”, “folk-physics” or “folk-psychology”, that seem to be evolutionarily primary. These serve useful functions even as “formal education” tries to disabuse us of magical thinking.

 

The final chapter, “Theology and Physical Sciences” traces the intertwining of scientific and theological thought through the ages. The author divides Christianity into four eras: Platonism, Aristotelianism (Thomist and Ockhamist), Newtonianism, and Twentieth Century (with the advent of quantum mechanics and special relativity); framing each of these eras in terms of ontology, epistemology, and cosmology. Examining the “seeming” conflicts between science and religion show that these often are related to differing and evolving frameworks of thinking. Thus, the hotly debated issues of the day change over time, and one sees this through the larger arc of history.

 

Overall, I enjoyed this compendium, but I do take issue with the title. I don’t think it’s ontologically possible to “imagine the impossible”. We can imagine many possibilities that may not correspond to physical or historical reality, but I think our act of imagination makes them exist as possibilities, even if only in thought. The possibility of imagining what’s possible and yet unrealized is what allows us to be creative, to bring out something new that wasn’t there before. You might call it magical. I call it living.

Updating a Definition of Life

How will we know if we have discovered extraterrestrial life on Mars, Venus, or the Moon? It might not use DNA or proteins or lipids; it might not be cellular; it might not even be carbon-based (although I think that’s unlikely given the uniqueness of carbon). If we discover some interesting chemistry, how will we know if it is biotic or abiotic? Can we recognize a metabolism that looks very different from the present core used by all living things on our planet?

 

One approach to check if what is observed corresponds to an agreed-upon definition of life. NASA has a pithy definition that’s both easy to remember and useful: “Life is a self-sustaining chemical system capable of Darwinian evolution.” It is also pregnant with meaning. Its heart is chemical (which I favor as a chemist!), but also systemic (with all that entails). It has the contrast of being self-sustaining and yet open to change via evolution. Must that evolution be Darwinian? What would it mean, and how is that distinguished from other evolutionary mechanisms? Is this definition too limiting? Is it too broad?

 

In their paper “Towards a General Definition of Life” (Origins Life Evol. Biosphere 2019, 49, 77-88), Vitas and Dobovisek propose an updating of NASA’s definition. Here’s the abstract.

 

Piece-by-piece, the authors analyze and critique the NASA definition that was formulated twenty-five years prior. Notably: (1) Thermodynamics is incorporated through the idea that life seems to stay away from falling into the equilibrium state; (2) Information becomes a central piece of their thesis; (3) Dynamic interactions between the living system and its environment are emphasized. Here’s their updated definition; it’s not as pithy, but perhaps a little improved over the original by being both more precise and more encompassing.

 

Life is a far from equilibrium self-maintaining chemical system capable of processing, transforming and accumulating information acquired from the environment.

 

The same journal issue contains a workshop report discussing “Hidden Concepts in the History and Philosophy of Origins-of-Life Studies” (Origins Life Evol. Biosphere 2019, 49, 111-145). There are twenty-five co-authors, and the discussion is indeed far and wide. One section considers the roles of necessity and contingency in origin-of-life explanations: Some explanations have a universal aspect; others have a historical aspect; and yet others seek to test the model by synthesizing (artificial) life. These three aspects were subsequently discussed in a definition of Lyfe (with a diagram illustrating these aspects).

 

The group also discussed two main strands in origin-of-life research. The first connects biology, chemistry and geology. The second connects physics, information theory and computation. For a while there was little cross-fertilization between the two groups, but that has changed in recent years. My own journey started with a little-known book by Jeffrey Wicken: “Evolution, Thermodynamics and Evolution: Extending the Darwinian Program” (published in 1987). I read it a decade ago but didn’t quite grasp its significance. More recently, I read “The Origin of Nature and Life on Earth” by Morowitz and Smith, combining the two strands. This was influential in pushing me towards tackling the question of proto-metabolism as my current main research thrust. You also see this in Vitas and Dobovisek’s updated NASA definition, where they weave the second strand into the first.

 

However, the 25-person panel also wonders if trying to find an agreed-upon definition of life might compound the problem, and this leads to what I think is the most interesting paragraph in their paper.

 

This brings us to a central problem with tailoring a model of the origins of life closely on a definition of life: there may be little reason to suppose that one could extract a causal “recipe” for life (in general, or specifically with regard to life on Earth) from a description of the fundamental properties of life (even assuming that we know what they are). It is not true in general that knowledge of the identifying properties of a material thing will reveal how it was produced. As an analogy, descriptions of quartz at the macro-mineralogical level (hardness, crystal habit, etc.) or the molecular level (SiO2) both explain how to identify quartz. Neither, however, explains how quartz is produced under natural conditions. Geochemists have discovered that quartz crystallizes in magma and precipitates in hot springs, and there are possibly other ways in which it forms under conditions very different from those found on Earth. Moreover, there is a fear in any subject that our observations are ‘theory-laden’ and so what appears essential to us is merely essential to the implicit theoretical commitments with which we approach life. The point is a lack of clarity about one’s commitments to the nature of life can lead to theoretical confusions and ambiguities over what needs to be included in a model of the origins of life, and in fact, a commitment to a theory or definition of life may not even be entirely necessary for the sake of making progress in understanding steps in the emergence of life.

 

Can a well-meaning and well-crafted definition of life cause us to look at life with narrowly blinkered vision? I don’t know the answer, but I should keep the question constantly in mind.

Clean

Should I stop showering? Should I stop using soap and shampoo? Is what I’m using actually soap? These are some questions posed by James Hamblin, a trained physician who also has a degree in public health, in his book Clean. It’s a breezy read, consisting mainly of anecdotes and vignettes as Hamblin interviews various folks about soaps, creams, cosmetics, dermatology, pharmaceuticals, microbiology, allergens, and more. No, you don’t need a vast scientific background, and the book itself is not heavy on such details.

 

The most interesting part was learning about the skin microbiome. The gut usually gets all the attention; and the health-products market is bursting with the latest and greatest in improving your gut microbiome. Hamblin thinks the tide is shifting and that caring for your skin microbiome could be the next big thing. He makes a good case for this by tracing the evolution of skin-care products over the years. The trajectory can be summarized by “less is more”. Cut out the soapy alkaline products and the constant washing away of what might be “good” microbes.

 

Hamblin doesn’t think that probiotics will make as much headway in the skin microbiome industry (as it did for the gut), partly because the penetrability of skin through topical use is limited. It’s difficult for oral probiotics to be appropriately directed towards the skin cells. Nor do I think most folks would want a bunch of subcutaneous jabs either, but I might be wrong on that. However, Hamblin thinks that there might be a market for prebiotics – not live bacteria, but chemicals that promote the flourishing of the “good” bacteria that already make their home on your skin. As a chemist who studies the origin-of-life, also known as prebiotic (“before life”) chemistry, I foresee much confusion in the near future when explaining my research area; akin to my cosmology friends who are thought to be knowledgeable in cosmetology. Or worse, astronomers who are confused as astrologers.

 

When visiting a department store, I steer away from the cosmetics and skin-health areas, where salespersons try to spray you with stuff. I don’t like the smells, the bright lights, and the many mirrors. I’m generally ignorant about the skin care industry, so it was eye-opening to read behind-the-scenes stories of health conventions where Hamblin chats up a variety of people I would normally avoid meeting. I should educate myself more in this area. There’s some interesting chemistry, particular in the chapter on volatiles. There are dogs that can detect cancers. I should collect examples for class, because I think students would find it interesting. (In a non-majors class, several student groups chose something related to cosmetics for their infographic projects.)

 

I was interested in what Clean had to say because I have occasional eczema flare-ups. They’re mostly mild, but they can be persistent and annoying from time to time. After reading the book, I’ve lessened my use of both shampoo and cleanser (apparently what I’m using is technically not a soap). I wasn’t using much to begin with (because of my eczema) and I already try to have quick showers with water that’s not too hot. Clean also reminded me that getting sunlight is good for our skin microbiome. As winter approaches, I need to be more deliberate about this. I’m still showering daily, and I don’t expect that to change. And yes, I will continue to wash my hands regularly with soap and water given we’re still in a global pandemic. (Hamblin would agree.)

 

Overall, I enjoyed my quick and easy read of Clean. And if you want to learn about Hamblin’s personal experience of not showering, read his book. It’s really about Skin, but perhaps that’s not as good a name for the book. While not earth-shattering, I learned some new and interesting things, and for me, that’s always a win.

Charades: Chemistry Edition

I’m not a fan of Charades – the game where your team-mates try to guess a word or phrase that you silently act out. I’m not dead-set against it either, and will participate if that’s what everyone in the group wants to do. I’m not particularly good at it, nor am I particularly bad at it. But I do think the core idea behind Charades is relevant to my core profession: teaching and learning.

 

Basically, you’re trying to communicate knowledge to others. But there are limitations. Barriers, perhaps. In Charades, you’re trying to communicate through gesture and without speech. Trying to communicate a concrete action such as “frying fish” is a relatively simple task. However, trying to communicate an abstract idea such as “honesty” is much more difficult. (Bet you’re thinking of how to act this out right this minute!)

 

At its heart, chemistry is abstract. It’s a nanometer-scale dynamic world we can’t easily see. Chemistry does manifest itself concretely in our macroscopic world through color changes, gas bubbles, explosions, and strange odors. But chemical understanding requires connecting the concrete with the abstract. We make models, draw pictures, write symbolic equations, in an effort to convey these connections. But it’s not easy for new learners encountering it for the first or even the second time. And it’s only too easy for us “expert” teachers to forget what that first confusing encounter was like.

 

I had no idea what was going on the first time I encountered chemistry in secondary school. A combination of guesswork, following a protocol blindly, pattern recognition, and some memorization, somehow got me through exams. So I have a vague memory of being in the blind fog of supposedly-learning chemistry, although I suspect I learned little. But I’m not able to articulate exactly how the fog eventually lifted, and how multiple “Aha!” moments led to my own conceptual grasp of chemistry. Learning can be systematic, but it’s also mysterious.

 

One of the challenges I face as a teacher is the Curse of Knowledge. Just because something is obvious to me doesn’t make it obvious to a student. Imagine you have a song or a tune running through your head. Tap out the tune. Do you think someone else could guess the tune from your tapping? The song seems so obvious to you with the tune in your head. However, someone else trying to identify the song solely from your tapping will find it very, very, very challenging. (Try it if you don’t believe me.) Now I don’t think teaching and learning chemistry is in the same realm of difficulty, but as teachers we should be cognizant of the curse when explaining chemistry – it may seem so clear and obvious to us, but it’s likely not so for the student.

 

Hence, one important thing we must do as teachers is to get feedback by probing what and how our students are learning. Early in my teaching career, I was regularly surprised by the lack of understanding from students when probing what they knew. These days I am less surprised (having figured out where many of the muddy bits are), but I still experience the occasional surprise usually in office hours while one-on-one probing a student’s knowledge, especially when it’s one of the ‘A’ students, who seemed to have earlier demonstrated the knowledge in a quiz or an assignment. It reminds me that students often have knowledge in pieces, or full of holes (like Swiss cheese)!

 

As I ponder the seeming obtuseness of my own “Aha!” moments, I’ve been thinking about the role of Surprise in the learning process. One idea I’m mulling is a short end-of-class or after-class assignment where a student writes down either (1) “something that surprised you from today’s class” or (2) “something you thought was a good reminder to something you already knew from today’s class”. I’m pondering the merits of a closed assignment versus a discussion board. Ideally, I’d like the closed assignment to then be populated in the Discussion Board. I’ll have to figure out how to do this.

 

Thinking about Charades also made me ponder the nature of my multi-modal teaching pre-Covid. I’d have visuals projected on the screen, real-time writing on the board, oral explanations, and lots of gesturing. Confined to my Zoom screen, the richness of this multi-modal environment is diminished. Yes, I have supplemental videos and other textual explanations that students can access asynchronously. But these miss out on the real-time back-and-forth that may contribute to a richer and more salient “Aha!” moment. I don’t have the statistics to prove it, but anecdotally I think the best “Aha!” moments my students have experienced are usually in office hours, as a result of the back-and-forth; part-Socratic and partly assisted by a white board. Asking students to write or draw as part of their explanation can be very telling.

 

Amusingly, the Journal of Chemical Education has a recent short article on ChemCharades, a simple game developed to help students learn the uses of glassware and some lab techniques. (See abstract and citation below.) It’s not rocket science.

 

 

Found an Argument

“I have found you an argument.” That’s the title of a short excellent article by George Bodner in the Journal of Chemical Education. I’d read this a long time back (the article was from 1991) but stumbled across it again as I’ve been reading and thinking about student misconceptions in chemistry. The article is based on a conceptual knowledge chemistry test given to entering first-year graduate students at Purdue – note these are students who were likely academically very strong students in their respective undergraduate programs.

 

Examples of concept questions to be tested are: “What are the bubbles in boiling water?”, “How does salt melt ice?”, and “What happens to the weight of an iron bar when it rusts?” While many of the students provide something reasonably close to a decent answer, a significant number do not. Sometimes only a small fraction of the students can come up with a cogent argument.

 

The paper’s title comes from a quote by Samuel Johnson: “I have found you an argument; I am not obliged to find you an understanding.” This fits with the argument made by Mercier and Sperbier that coming up with reasons or explanations is often lazy and post-hoc. It’s why I try to emphasize the explanative parts of chemistry, often the hardest for students. I’d like to think that’s the value-added of having an expert interlocutor for students to interact with in real-time.

 

An example that Bodner discusses is one that I have emphasized strongly to my first-semester G-Chem students this semester. The prompt is: “Everyone knows that sodium metal reacts with chlorine gas to form sodium chloride. Explain why. In other words, what is the driving force behind this reaction?” Bodner reports that at first students mostly said “because of a decrease in Gibb’s Free Energy of the system”. Further prompting of why led to “a significant fraction not being able to answer the question”. Scarily, and perhaps not surprisingly: “By far, the most common explanation was based on the assumption that the octet rule drives chemical reactions.”

 

Every year I try to emphasize to my students that the octet rule is simply a rule of thumb for identifying good Lewis structures, and should not be invoked for explanative power. I even have a Happy Atoms Story to go along with this part of class. We explicitly go through the energetic calculations showing that the first ionization energy of sodium is not sufficiently compensated by the first electron affinity of chlorine. Then we invoke Coulomb’s Law and define lattice energy. Before all this is done, we’ve already discussed bond forming and breaking across a range of examples illustrating the general bond energy curve.

 

Here’s a snapshot showing some of the erroneous answers from the incoming chemistry graduate students.

 

But it gets worse…

 

The purpose of Bodner’s paper is not to ridicule students. It is aimed at us, the instructors. We should be thinking carefully about our teaching – it needs to be more robust, and we need to pay explicit attention to common misconceptions and the “Swiss-cheese knowledge” of our students. Here is my paraphrase of Bodner’s observations and conclusions: (1) Students are often only good at applying domain knowledge narrowly, and they need more “cross-training” examples; (2) Misconceptions can be quite sticky and difficult to dislodge; (3) Students can “know stuff” yet lack in understanding; (4) Misconceptions can often be caused inadvertently by instructors.

 

I will close with a different example. Here’s the prompt: “Ice is less dense than water, but steel is almost eight times as dense as water. Explain why both the Titantic and the iceberg it hit were able to float on water.”

 

One of the answers given by a student: “The Titantic was made from titanium, not steel.”

Colors in Chemistry

I recently finished the module on Stoichiometry and Chemical Reactions in my G-Chem class. The last group of reactions we looked at were redox reactions. Of these, one of the classic demos is the metal displacement reaction. I usually put in zinc or magnesium, a grey and shiny metal, into a blue solution of copper sulfate. Moments later, the grey metal begins to dissolve, the solution turns colorless, and out pops a brownish solid – copper metal. Our G-Chem lab has the students run through what’s known as the “copper cycle” where they get to observe these changes and more – although in a Covid year, they will likely not be able to actually do this in person.

 

The metal displacement reaction I described above can be represented by the following chemical equation.

 

Zn(s) + CuSO₄(aq)  -->   Cu(s) + ZnSO₄(aq)

 

The students learn how to write the net ionic equation and identify sulfate as a spectator ion that does not participate in the reaction.

 

Zn(s) + Cu²⁺(aq)  -->  Cu(s) + Zn²⁺(aq)

 

We also break up this net ionic equation into its two half-equations to track the loss and gain of electrons in the redox reaction.

 

All this is accompanied by nice “molecular” level pictures of what’s going on in solution. Here’s one from the current textbook we’re using. 

 

Notice it juxtaposes the microscopic world pictures with the macroscopic picture you’d observe in a real-life demo. Interestingly, the particle picture of zinc metal colors the zinc atoms grey, and similarly the copper metal atoms have the reddish-brown of a copper metal. This is somewhat misleading. Bulk copper metal might be reddish brown, and bulk zinc metal might be greyish-silver, but the atoms certainly don’t have those colors.

 

The day after my class, I was reading another chapter from Multiple Representations in Chemistry (blogged about here and here), which discussed misconceptions students have about bulk properties such as color. This particular zinc-copper displacement experiment was one of several such examples. The chapter described a study probing the conceptual understanding of high school chemistry students navigating between the macroscopic, microscopic, and symbolic views of chemistry (known as Johnstone’s Triangle). Not surprisingly, the students didn’t really understand what gives rise to the color of a chemical substance that they can see – and many of them thought that it came from the color of individual atoms.

 

Horrors! I wonder if my G-Chem students have the same misconception. I certainly talked about the observed color changes. When copper precipitates out of solution, you can see the brownish metal. This and the disappearance of the blue color, which I attributed to Cu²⁺ ions in aqueous solution, was connected to the reduction half-reaction Cu²⁺(aq) + 2e^- --> Cu(s). Similarly the dissolving of zinc metal and the solution turning colorless was because of the oxidation half-reaction Zn(s) --> Zn²⁺(aq) + 2e^-, and I probably said that Zn²⁺ ions in aqueous solution are colorless.

 

I think the students comprehend that individual atoms in the solid metal are not colored per se. We went over this the very first day of class when we discussed atom representations, and I occasionally make reference to it when molecular pictures show up again in chemical bonding. “Atoms aren’t colored! This is just a standard representation chemists use!” But I hadn’t discussed the ions. And the textbook picture “colors” the dissolved aqueous ions the same color as the atoms in the bulk solid. Needless to say, they are not blue and colorless for Cu²⁺(aq) and Zn²⁺(aq) ions respectively. I’m not sure what the students were thinking about the different colors of aqueous solutions because I didn’t emphasize this point. I should check but haven’t had time to do so, as my class sessions are usually very tightly scripted.

 

In one of our early G-Chem labs, the students make a standard curve for a red dye solution, and then use it to measure the concentration of red dye in a Kool-Aid solution. There is some discussion about what the absorption spectra of the dye looks like as we discuss Beer’s Law and how to set the UV-visible spectrometers to “lambda-max”. I’m not teaching lab this year, and because of remote teaching, I didn’t do my usual activity of having the students use hand-held spectroscopes and look at colored solutions to see what light gets through and what is absorbed. So I’m not sure my students have a good notion of why they observe color in a solution. The textbook picture doesn’t quite help where the molecular level picture of CuSO₄(aq) has a darker blue background than the ZnSO₄(aq) with a lighter blue background, supposedly representing the “blue” of water. I have mentioned to the students a couple of times that water is not blue even as I use my blue marker to draw beakers of solution on the white board. I might be adding to student confusion without knowing it.

 

What am I learning from all this? Next year when I teach first-semester G-Chem again, I’m going to pay attention to this issue of color and try to address potential misconceptions systematically by building it into several places in my syllabus. And I need to make a stronger connection to what students are seeing and doing in lab. I haven’t taught the lab for a number of years, and that’s caused me to “forget” to make some of those stronger connections between lecture and lab courses.

 

On top of all this, I think the students might further trip up when seeing the simple picture of metallic bonding. The chapter I read discussed students viewing the metal “atoms” in the bulk solid as metal ions – with a sea of separated electrons in the nooks and crannies between the atom/ion spheres. And these pictures have colors. Who knows what the students are actually thinking? I’ll need to pay attention to this again next year. But right now I’m just trying to finish this Covid semester without burdening the students with more details. As to the specific zinc-copper metal-displacement, I have another shot at it next semester when we cover electrochemistry in detail, so I’ll try to design an activity to probe what the students are thinking and how we can correct any misconceptions.