It’s time for another General Chemistry class update where I
am threading the theme of Elements across the semester, culminating in a final
project where the students invent and justify new elements. For my previous update,
click here.
In October the students completed the third scaffolding
assignment: “Invention of New Compounds”. Since we had just finished ionic and
covalent bonding, and the properties of ionic and covalent compounds, the
students had to propose a new compound based on known elements. What qualifies
as new? An Internet search of the compound should not yield any useful
information. Besides coming up with a name and chemical formula, the assignment
required a description of structure/shape, physical properties, and potential
uses of the compound (or why it might be inherently interesting). Students
could choose to work individually or in small groups.
On the whole, students proposed a range of compounds. Some
were very interesting, and others rather pedestrian. Many students (and/or
groups) had trouble really thinking out of the box so they came up with simple
substitutions where a known element was swapped with its radioactive “heavy”
counterpart. Astatine, Tennesine, Seaborgium, Francium, all had their moment of
glory! The students recognized that some of these elements were radioactive,
and were therefore short-lived. Suggestions included being used as poisons and
explosives.
It was a useful learning experience, because I realized that
even when students proposed ionic compounds (and suggested properties in
alignment), many drew me covalent structures instead of using the unit cell in
solid-state compound description. (Admittedly, only one class period was spent
on cubic unit cells while I rammed home Lewis structures over several class
sessions.) Also because radioactivity was covered very early in the semester,
students had forgotten that forming a chemical bond between a radioactive
element and another element does not change its decay rate. I read several
statements related to how non-radioactive elements would stabilize radioactive
elements through chemical bonds. Students also had difficulty coming up with
analogies to justify the properties they had listed. We went over these issues
in class, so it was a good learning moment, not just for my students, but also
for me.
The students have received their next assignment, a proposal
draft of their new element. I assigned them into groups based on what I had
seen from their work over the semester thus far, but I also took their
preferences and some contingencies into account. The proposals are due in a
couple of weeks. Here’s the first two lines in my instructions: “Your Final
Project is to propose a new element, and justify why such a new element should
be created. You may assume it is technologically possible but very expensive
(this is what Tony Stark does in the movie Iron Man 2) and you are going to
pitch the idea to investors who are also well-versed in science.” Then follows
a list of parameters and things to consider as they come up with their new
compound. Their final poster presentations will be in roughly five weeks. It
will be a larger session because they will present at a symposium involving all
the students in the living learning community (~110 students). I’m excited to
see what they come up with!
Not related to the final project, I am experimenting with
take-home exams this semester. While on average the students did well on the
first exam, they did not do well on the second exam. (I give the students the
full 2% associated with turning in the exam regardless of how they do. They
take it under “exam conditions” as practice for the final exam, which is timed
and closed-book.) I suspect that because it does not impact their grade, they did
not study as hard for it. I took the opportunity to provide a learning moment
(in the form of a pep talk) as to why they need to study as if these exams
“counted” if they really wanted to prepare well for the final exam. The third
exam is coming up this weekend, so I will devote half my Friday class to
Q&A. I normally do this for the class-before-the-exam in my other classes
when they are in-class exams. But I hadn’t done it this time around, so I need
to go back to that practice. We’ll see how it goes.
Other than that, classes are going well. We’re somewhere
around week ten, so there’s still five weeks to go in the semester. Whew!
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