First Day of Chemistry!

So... this post is 2 days late.  Our first day of the new semester was on Monday.  Would you believe we're already off schedule?  Thank you inclement weather-- school was dismissed at 12:10 today, and will be closed tomorrow.  Yay for snow days, although there's nothing like being one and a half days behind after the first week.

I am teaching all standard chemistry this semester.  I currently have 57 students between three sections-- I'm sure that will change.

The first day of class, after all the necessary introductions and paperwork, I did the "Exploding Can" demo:

The Can

You can see a YouTube video of it HERE (I did not makes this video, despite using the same brand of coffee).

I set up the demo by explaining to students that methane is a gas that is lighter than air as I was filling the can.  I dimmed the lights and ignited the methane coming out the top hole.  I told students to record their observations and to keep their eye on the flame at all times.  The flame burns for about 3-5 minutes, culminating in a small explosion that scares the bejezus out of the students..

With their groups at their tables, I then had students story board the particles at the beginning, middle, and end of the demonstration.  The results were pretty interesting.  Here are some highlights from my 3rd block:

The particles are multiplying, building up pressure, which caused the can to explode

Particles starting off at room temperature and heating up because of the flame.  The additional heat causes them to move faster and crash together harder until they cause an explosion.

The methane and oxygen particles rise and move upwards during the demonstration, causing the can to explode.  The also expand because of the heat from the flame.

It was really interesting for me to see just how many misconceptions these students have about all sorts of topics.  For example, most groups didn't draw the flame.  When I asked if there was a reason, some told me because flames aren't made of particles.  Some told me that flames are oxygen, which isn't a particle.  Some told me flames are just heat.  One kid told me the flame was made of lighter fluid, and I just transferred it to the can.

Most groups only drew one type of particle, with a very small handful including air or oxygen.  When I asked if the can was made of particles, most told me no, the can was made of metal.

I would say about 50% of the groups said that the particles were multiplying in the can as the demo progressed.  When I asked for evidence to support this idea, some said because the flame was going into the can.

I didn't really have a great "wrap up" for this discussion, expect to tell the students that all groups had some correct ideas and some incorrect ideas.  And I promised them that by the end of the course, they would be able to fully explain why the can exploded.  I also said that chemistry is the study of particles-- particles are what cause everything to behave the way it does.  Through chemistry we can predict what different types of particles will do in different situations.

Yesterday, students took the Chemistry Concepts Inventory.  I haven't even run their answer sheets through the Scantron yet.  I can't imagine their scores are going to be very impressive based on our class discussions thus far.  We also had a lab safety day, which I felt was absolutely imperative before the Mass and Change lab.  Traditionally, I have spent multiple class periods on safety and lab equipment.  This year, I limited it to one day in hopes that I will be able to impress what I didn't cover in detail upon them during the many lab activities and board meetings.

I gave students a worksheet that I have used in the past called Identifying Improper Lab Behavior.  Previously I have used this activity as an evaluation or homework assignment after we have covered safety.  The worksheet has 6 scenarios where students are doing obviously incorrect things.  Students have to read and highlight the unsafe behaviors.  There is also a checklist where students have to match a particular unsafe practice to the scenario(s) where it occurs.

To add a modeling "spin" on the activity, I then had students in groups create a list of laboratory safety rules that would have prevented all of the unsafe behaviors:

We held a board meeting to share and discuss each group's safety rules, then came up with a consensus list of rules for the laboratory to be copied into our laboratory notebooks (which about 2/3 of my students didn't bring to class- I was spoiled last semester with exceptionally responsible students).

Today's original plan was to complete the Mass and Change lab.  But... we had an early dismissal that caused us to be on a modified schedule.  We barely got started on the lab.  On a positive note, the students conducted themselves in an excellent manner in the lab for the short time we were there today.  I was worried after the first day of class that the maturity level of my students was going to be too low for many of the more complicated labs.  But my hope has been (tentatively) renewed after this morning!