Unit 2 Reflections: PVTn Labs

It's no fail-- my students always surprise me.  Sometimes for the better, sometimes for the worse...

I was having some trepidation about how seriously I should pursue calculating the pressure in a manometer flask like so:

It's not a state standard, so I was going to play it by ear as the students completed Worksheet 2.  If they seemed to understand the concept quickly, I'd have them do those problems.  If not, I wasn't going to fight the battle.  Go figure, they mastered the concept in about 30 seconds.

Overall, they did really well with Worksheet 2.  I would say 85% of the class was even successful at the pressure unit conversions at the end with minimal help from me, and I didn't even tell them it was coming.  Granted a good portion of my students still freeze up like a deer in headlights when they see a conversion, but they can do it with some goading.

We ended yesterday with a Boyles Law lab.  The AMTA lesson plans have students performing 3 labs with Vernier equipment:  P & V, P & n, and P & T.  We don't have Vernier equipment at my school, however I personally have a single LabQuest and probes of my own.  I have mixed feelings about having students do too many Vernier labs, regardless of having the equipment or not.  I feel the students often are intimated by the equipment and software, which causes them to miss the entire point of the lab.  At the same time, I've watched many college students continue to struggle with the Vernier labs.  It would be nice to give my students the exposure now so they're more comfortable with Vernier in college.  I don't think there is a "best" answer when it comes to using Vernier with standard high school chemistry students.

Anyways...

My compromise was for students to do a simple Boyles Law lab using pipets and textbooks that I found on Flinn's website:




Then for Avogadro's and Gay-Lussac's Laws, my plan was to use the Vernier equipment and demonstrate the lab the students were supposed to do from the curriculum.

The Boyles Law lab went pretty well-- it was quick and straight forward.  My first two classes of the day figured out the relationship easily for the most part. Most of their boards looked something like this:

By the end of the day, I found there were more and more student procedural mistakes.  The most common was measuring the length of the water instead of the air, giving them an incorrect graph (this one was doubly incorrect):

I was bummed about their verbal conclusion.  And confused about their particle diagram.

The mathematical expression was really hard for them on this one.  I've found here most students just don't understand inverse relationships.  I showed them the concept of P=1/V, but I'm not sure how many took anything away from the discussion.

The Vernier demos were a huge flop.  The kids were bored to tears.  They didn't understand what I was doing, they just blindly copied the graphs on the screen into their lab notebook.  Seriously, there was zero advantage to pulling out the Vernier equipment for a demonstration in this instance.  I might as well have just talked at them for half the period.

What was most helpful, again, was the PHET simulation.

We also did a KMT reading out of the textbook, or tried to.  I wanted them to read thoroughly and write, but we only had about 10 minutes left at the end of the class to do the activity.  It became more of a "scan for the answer" activity, which I hate.

Tomorrow we will tackle PVTn problems using the combined gas law.  While I plan on using the PVTn charts, I'm not teaching the factor/train-track method they showed us in our modeling workshop.  Not happening.  I'd rather the students be able to plug and chug into the equation that they will receive on the back of their periodic table when they take the EOC.