Unit 3 Reflections: Icy Hot Lab

Snow days.  Don't get me wrong, I love them... but they sure are making it hard to get through everything before the EOC.  The EOC date does not change no matter how many days we are out.  Yesterday was another snow day.  We picked up today with the Icy Hot Lab, and had to cram it into one day.

I haven't gotten to begin this unit as I would have liked with all the interruptions.  Wednesday I was missing a large portion of my classes due to paperwork for the ACT.  All we really got through was the Energy Reading Study Guide.  We didn't even have enough time to discuss the reading and study guide in class, so I had no idea how much understanding they had of energy.  Not surprisingly, my thinking-phobic, non-conceptual students love assignments where they just have to hunt and peck for the answers.  It was the best "work" I've seen out of them this year.

Today, I put some of the main points from the reading into a PowerPoint-- because I feel like this concept of "energy accounts" is going to be difficult for them.  Or maybe it's just difficult for me.  Anyway, I wanted to try to drive home the idea more before they have to apply it to a graph.

In a perfect world, I would have done the Icy Hot Lab over two days.  In that perfect world, we would have discussed and planned part 1 as a class.  We would have white-boarded and discussed our results from part 1 before going on to part 2.  But... that couldn't happen.  Monday, I have to proctor a state writing assessment.  Tuesday is when the juniors take the ACT.  So we crammed everything into today and will discuss results whenever we can.

I had to make some changes to this lab.  First, we used hot plates instead of ring stands/bunsen burners.  Our ring stands are pretty chintzy and our iron rings are ridiculously tiny-- supporting a beaker of boiling water over a bunsen burner was not going to happen safely.

The world's worst hot plates.  The entire casing gets hotter than the actual burner.

Secondly-- no Vernier.  :(  This is one case where I truly would have preferred collecting data and graphing with Vernier if it were available.  Instead, I had my students manually record the temperature every 15 seconds with digital thermometers.  I have no idea of 15 seconds was an appropriate time interval-- looking over the data, I'm not sure if we're going to see good curves.

There was no shortage of "teacher mistakes" with this lab.  For example, I forgot to have them make a hypothesis of how their curves will look.  Big oops!  I was just so worried we wouldn't have enough time to execute the lab that I completely forgot.  I also forgot to demonstrate how to take accurate temperature readings with my first class of the day.  I realized a couple minutes into the experiment that most groups were just letting the thermometer sit against the bottom of the beaker, giving them artificially high temperatures right from the start.  I was able to prevent this in my later class periods.

Another problem I noticed early in the day was students trying to fudge data-- they had an idea of what they thought should happen, so they kept trying to make the data match that idea (which is going to totally botch their curves).  I didn't get as much time to address this teachable moment as I would have liked, but I did make a point to tell all students to record what the data says even if they believe it may be incorrect.

When it came to the freezing of lauric acid part, the teacher mistakes were still in full force.  Again, I forgot to tell my students in my first class the importance of keeping the lauric acid hot before you begin.  Most of them grabbed the sample and let it sit a few minutes while they got organized.  Their samples were well under 50C when they began recording temperatures, giving very linear data.  By the time I noticed this, the groups were so far into the data recording that there wasn't time to start over.

Test tube of lauric acid cooling and freezing as it sits in a beaker of cold tap water

I just hope we get usable data out of this experiment.  I don't want to create/reinforce existing misconceptions.  Also, students will be writing their first lab report over this lab and I don't want it to be harder than it needs to be.  If the data is erratic, they are going to struggle with their conclusions and questions.