Author: Jon

How I teach Infrared Spectroscopy

You can find here a folder of material I use to introduce IR spectra interpretation in a 70 min mixed SL/HL class.  It is tactically hyper-efficient but structurally sub-optimal: splitting this into two or three sessions of shorter duration could possibly be better.  But, hey, I teach a 240 hr syllabus in 150 hours; I can have my kids for an extra year and we would still not make 240! Sequence-wise, I teach 10 (organic chem) -> Index of Hydrogen Deficiency -> IR -> 20 -> NMR.  I find IHD a generally useful tool that complements structure determination. In this intro class, I first set the context with general idea of spectroscopy (5 min).  My hook is usually, “let’s say the shady dude at the corner tells you ‘it’s the good stuff’ – maybe you don’t trust him, but how would you know?  What…” [pause] “…Way of Knowing do you have?” [groans] For the spectroscopy intro I use my diagram on absorption spectroscopy on wikipedia, which have just all the needed graphics and no extra: (I never cease to be marvel at how the 2010-2011 drawings stand the test of time.)  While we are here, I point out how weird IR spectra are: wavenumber as unit non-uniform horizontal scale baseline on the top (signals go down) …and promise them that in just 25 minutes they will be able to...

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January update for TRE

The following material has been added to the Teacher Resource Exchange folder: Tests by JC IR teaching materialsby JC worksheet / activities uploaded by B-CJ and PB I was transferring material from the myIB TRE group, but progress is stalled while I await responses on copyright / link issues (see discussion here). — Details Tests These are 9 tests I wrote in 2017.  All tests have 40 points, the same expectation as the IB papers of 1.5 pts / min. The recent papers are set in the sans serif fonts (as with the new IB papers) and uses the...

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2018 May IB chemistry practice schedule

I created a “past paper practice schedule” to help my Y2 students to prepare steadily for their upcoming exam, and you can find that here. HL Past paper practice schedule (2018) There is a separate one for HL and SL students, both meant to be printed on a portrait A3 sheet (and posted on their study space).  My proposal is for them (or your students) to do at least the top paper properly.  By “properly” I mean specifically: timing themselves, preferably on each question, but at least for the time it takes to do the entire paper; marking their level of certainty for each response, so they are aware if they have gotten a question right just because they were lucky, or if they thought they understood something but didn’t; score their answers, so they can reflectively analysing their mistake. This is the key to the whole exercise: practice without reflection makes permanent and not perfect. To do this properly would take 2-3 times the amount of time just doing the past paper would take (e.g., to allocate 2 hrs for a SL P1, or 4-5 hrs for HL paper 2; allocate time accordingly).  If they have more time, or targets more rapid improvement, they can additionally do the second paper.  The admonishment is that if they must choose between doing one well or doing two poorly, always choose to do...

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The secret area in acid-base titration

With phenolphthalein (in 50% EtOH) as the indicator, and base as the titrant, it is common knowledge that the solution turns from colorless to magenta.  However, with careful sub-drop addition, the solution actually first turns milky-white, then milky-pink, before it clears up to a transparent pink at the end point: After learning about the existence of the “secret area”, many students did the titration with utmost care.  It was fun (and pretty tense) to watch. Chemistry-wise I am not too sure what is precipitating.  (Both the acid / base forms of phenolphthalein should be completely soluble.)  Surely I am...

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