Chemistry, Contingency Planning, Laboratory, Pedagogy

Moving a (physical) chemistry lab online

The last post discussed some epistemological considerations (roll with it) on moving chemistry labs online, sharing some concerns about trying to teach technique via fancy swipey-wipe interactions (roll with it).This one aims to be a bit more grounded. If we were to move a lab online, what might it look like? I am going to go through my first draft of thinking for moving a physical chemistry lab online below. The headline considerations for me are:

(1) not to create busy work for the student for the sake of it;

(2) some bits of lab work aren’t really that great, so let’s not try to just replicate; and in complement,

(3) when we are all back in the actual lab again sometime in 2027, maybe there are some bits of this online malarkey that would actually be quite useful to keep in place.

In other words, my focus is not on replication, but on looking to build a decent learning experience.

Let’s flash!

My prototype experiment is a pretty standard one on flash photolysis of azobenzenes, built on the experiments described nicely in this J Chem Ed paper. We use this as a basis for an experiment in our third year, and this is the year we focus on teaching experimental design, using our “unfinished recipe” approach. That is to say, students do a recipe lab to get used to the experiment, the kinds of experimental protocols, and data outputs, and then follow this up with a non-trivial investigation based on the kinds of things they learned in the first part. Our “Part 2” is based on the recent paper described here; it asks students to explore pH effects, and if they are really good, to go hunting for a transient.

I like this experiment because it is based on photochemistry – enough said? But also it is a good one for students to pull a lot of what they already know – kinetic analysis, simple techniques (UV/vis in kinetics mode), cis­-trans isomerisation, etc – and apply it to a new analysis (for them). The experimental technique, while reasonably straight-forward, requires a bit of black art at times, and you see students who will get really good traces and those who get not so great ones, just based on some timings when they actually do the experiment. I want students to get things like considering timelines for experimental measurement (my homage to Porter), working with trickier kinetic decay curves, and making reasonable judgements about mechanisms from their data. For students who want to push a little more, hunting for the transient based on the information from the Larsen paper is a good trip to go on.

Moving online

Now I know at some point I should write down all the learning outcomes I want but I am not going to do that because it is just too much of a pain. Instead I want to frame my online lab in terms of technical competence and syntactical knowledge. Just a little more detail on what I mean by those are in the previous post, but it will become apparent below if you can’t be bothered to go back to that.

1. Technical competency

As mentioned I don’t really see much point in going down the road of trying to recreate a simulation of the experiment online. They do exist for flash photolysis, and again I make no judgement on these, but my own purpose here is to take students through an actual experiment and understand how they would complete a task to obtain the data they will be presented with. A cost of moving online necessitates, I believe, an acceptance that we cannot teach experimental technique as well as we could do in person. So what can we do? We do have videos of our experimental techniques, made in our labs. At the very least, we could show these videos?

This seems a bit unsatisfactory, and very passive. I want students to really think through the procedure; live through the considerations that they might have to make in practice. Key ones here are the solution concentration (a desirable absorbance of < 0.2 at max) and the kerfuffle of getting a flash (we use an old camera flash) and recording the subsequent decay. The first is reasonably routine – we could provide students with an absorbance spectrum of the stock and ask them what they wanted to do with it; the second is impossible to role-play – simulation or not. Therefore I am thinking of getting students to critique the procedure as presented in the video. This seems like a sensible way to get them to really think through it. Our procedure could be improved, no doubt, in parts, and a nice task for students would be to talk about how they might do that. This is an example of how I think we might actually improve the status quo, and this critique can feed into some discussion later (for example how different events in this photochemical process might be studied).

2. Syntactical knowledge

The complex learning framework that I use to guide my own thinking on labs aims to describe a lab environment in terms of what students need to draw together when completing laboratory work – the combination of, in this case, knowledge of kinetics and analysis, understanding of photochemistry principles and timelines, knowledge of using the UV/vis spectrometer and application of the combination to address a laboratory-based problem. In simple terms, I do not want to use this lab to teach kinetics, but want students to bring their kinetics knowledge to this environment and apply it alongside their other relevant knowledge and experimental skills to address a laboratory-based problem.

How do we move this online?

I think to answer this I need to write out what the component bits are in each stage of the experiment, so that I can see what it is students are “drawing together”.

In part 1 of the experiment, the focus is really on training about the approach:

  • Running each of the solvents in turn (toluene, cyclohexane, acetone), including one at a range of temperatures and extracting kinetic data;
  • Curve-fitting to obtain rate constants, and in one case Arrhenius parameters;
  • Data presentation and interpretation (in terms of mechanism)

This is all pretty routine, but drawing together in an online version means, along with the technical aspects described above, students will need to be given data to run through the processing, and present some summary findings about what this means in terms of the mechanism (essentially a discussion based on polarity). Do we simulate this data based on some student prompts, or do we just give them some data sets? I don’t know yet, but I would like the former. I’d like them to think also about data quality and what might be affecting it.

In part 2 of the experiment, students have to design a pH study of a water-soluble azobenzene, and if they wish, go transient-huntin’ (unlike the Larsen article, we generate point-by-point spectra). This means they need to plan out things like:

  • Deciding on what pH range to study and how to prepare those concentrations ((un)surprisingly this is a pretty major challenge for students);
  • Repeating the analysis for solutions at different pH
  • Exploring different wavelengths beyond the bleaching peak to see if they can find transient
  • Comparing transient and bleaching kinetics

This second part is much more student-driven, and takes them a lot of time in the lab normally just to even scope it out. So in moving this online, I’d like to replicate that – we really want them to think through experimental design. Online, this might need more guidance and dialogue stages; prompt first thoughts on the overall scope – what will the purpose of a pH study be based on what they know from the first part of the experiment (polarity dependence); how could they go about making a study; what are the technical aspects of that (pHs, concentrations, etc); how might they find transients; what would a comparison of transients mean. I can see this working out quite nicely (in my head!) but wonder about how that dialogue would be managed with ~150 students so that each gets to have their own input into “their” experiment. That consideration (workload of demonstrators aside, albeit hugely significant in terms of what can actually happen) is why I think simulated data would be good.

Assessment

Another significant issue is that of assessment. We could of course continue with the major report we expect of students from these two-part experiments – they are beneficial in preparing students for later pieces of major writing such as their thesis. A concern is that if we need to engage students a lot more in dialogue on the way, they will already be putting quite a lot of work into this – so we need to capture that in what would previously have been a lab mark. Also, I think I would like to hear from students as well; especially in relation to their understanding of the technique and how it works. Perhaps there is scope for that, through an online presentation, and that this would, in some small way, make up for the lack of completion of the experiment. “Category is: explain flash photolysis with 5 pieces of Lego…” Now that would be an improvement on the status quo!

Oh dear – so much to do… And this is only one experiment!