Sources of Error

I just created a short article titled, "Sources of Error" for students to read and annotate.  This is because students often confound mistakes with sources of error, thinking that both are bad.  Sources of error are present in any laboratory activity, and understanding them demonstrates that you understand how variables affect the outcome of your experiment.  Sources of error should always be discussed in a lab writeup or lab summary.  You can see it here.

Stoichiometry on Teachers-Pay-Teachers

I finally got one of my canvas and moodle files posted for sale on Teachers-Pay-Teachers.

I've been meaning to do it for 2 years, ever since I started writing those monsterously sized question banks.  I just never got around to cleaning them up good enough for showing to the public.

I took 12 quesion banks for Stoichiometry (moles-to-grams, grams- to-moles, and grams-to-grams) and put them in both Moodle and Canvas.  They look the same in both.  I even put examples into my moodlecloud demo site,, with a "demouser" login so that people can check them out.

What I haven't done is clean up my amazing Drag-and-Drop virtual card sort for stoichiometry and for dimensional analysis.  It really annoys me that something so useful would be part of the core functionality in Moodle, but isn't even being considered yet in Canvas.

Oh, well....

I need to get onto some of those other question banks I've been meaning to list.  With all the downtime because of this coronavirus thing, I could have gotten a lot done.  Instead I blew it - wasted almost 3-weeks!  Now spending my time writing online curriculum so that we can do distance learning in my shool district.  So much potential....just.....lost.  Next time.


Drag & Drop Problems

I've been developing in Canvas for a couple of years now, resorting to good-old php and html sites when I need something Canvas can't do.  After spending a extraordinary amount of time trying to learn more HTML5 so that I could create drag-and-drop question type, I found that there are three versions of that question type now a part of the Moodle core.  I experimented around, found that I could make exactly what I wanted, created it, and published it as an LTI tool.  Then it turns out that Canvas needs to connect to Moodle through SSL.  I buy a certificate, and then find out that of all of Moodle's question types, the Drag-and-drop does not work as an LTI.

What the heck.  Is there no way to get a drag-and-drop question in Canvas??

Here's why this is important.  A drag-and-drop question can be used as a learning tool.  I am trying to teach stoichiometry, and I really want to do a card sort to teach the dimensional analysis.  I could lay out a grid (some people call them train tracks) on a desk, and then have cards with numbers and units for the Given, Molar Masses, Mole Ratio, etc.

Then it hits me - drag and drop is exactly what I'm doing with a placemat-sized grid an a zillion note cards.

If only Canvas would support Drag and Drop question types, or Moodle's LTI worked well with Canvas.  I'll take either.


Solutions Molarity & Dilutions Practice Available

The site has added unlimited practice problems for two categories of solutions, molarity & dilutions.  You can calculate the molarity of a solution given grams or moles, or calculated the volume, moles or mass of a substance given two of the variables.  Many can me done with just a calculator, but you should download a periodic table (Texas Chemistry STAAR Reference Materials) for the molar masses you will need.

Dilutions calculations are also on-line.  They are pretty straight forward.  Given the equations M1V1 = M2V2, calculate molarity or volume given the other variables.  Right now, all volumes are in liters, so there is no conversion to mL necessary, but that is expected to change in the near future.

Just go to