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The University of Pennsylvania- Master of Chemistry Education Program (MCEP)
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Mark Hayden e-Portfolio The University of Pennsylvania- Master of Chemistry Education Program (MCEP) |
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Comprehension of
Chemistry Content Course
Enduring Understandings The participant has grown to have stronger comprehension of science content as described in the program and course Enduring Understandings |
| GROWTH |
This entry will
demonstrate how
I have grown to have a stronger comprehension of science content as
described in the program and course Enduring Understandings by:
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| BASELINE EVIDENCE |
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PROGRAM EU: Chemistry is an
experimental science where bridges are built between experimental
observations and underlying concepts. (see EU source) Before entering the MCE program, I
understood that bridges are built between experimental observations and
underlying concepts using models (i.e. physical, mathematical,
etc.) However, what I
didn't appreciate was the extent to which computers are now used
to make those connections. Considering this, my baseline was
virtually zero for the types of activities that we would be doing in
Information Technology and Experimental Chemistry (CHEM502). In
relation to the specific content at hand, I also had never heard of a
transition state. In order to show this, I've included an image
from one of my classroom PowerPoints below. Readers will note
that the transition state is not labeled on the diagram. The
only aspect of the diagram that I was emphasizing to my students was
the energy difference between the reactants and products.
 CONTENT EU: For any acid HA, the relationship between the pKa, the concentrations existing at equilibrium, and the solution pH is given by: pH = pKa + log [A-]/[HA] (see EU source) One of the basic understandings
that is a foundation for acid/base chemistry is the concept of a
buffer. While studying buffer systems in Biochemistry (CHEM504),
I was asked to complete a problem on the board. Readers can view
the problem itself, as well as my particular response by clicking on
the links below. While attempting to complete the problem in
front of the class, I treated the acid (nitrous acid) as a strong acid
by assuming that it would dissociate completely in the buffer
solution. This can be seen in my calculation where I attempt to
calculate the moles of acid directly from the molarity of the nitrous
acid.
CONTENT EU: Atoms
obey the laws of quantum mechanics and have energy levels- Vibrational
Energy (see
EU source)
At the end of each quiz in MCE
Molecular Spectroscopy (CHEM507), we were asked to complete a
"preview" section that related to upcoming concepts. The idea was
to establish a baseline for items that were coming in the following
months. Below is a preview question related to the vibrational
modes in carbon dioxide. Readers will note that I was completely
clueless, which clearly indicates a baseline of zero for that topic.
Vibrational modes preview question
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| EVIDENCE OF GROWTH |
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PROGRAM EU: Chemistry is an
experimental science where bridges are built between experimental
observations and underlying concepts. (see EU source) GAMESS Problem Set #1 (Concepts: Bond Energies, Reactive Intermediates) CHEM502 During my participation in
CHEM502, I started to appreciate the role of technology as a bridge
between experimental observations and underlying concepts.
Mostly, I recognized computer modeling software as an incredibly
powerful tool that can catalyze the creation of new chemical theories
by providing an additional method for experimentation and
visualization. Below, readers will see evidence from my Games
Problem Set #1. First, I have provided the reaction coordinate
for the process. Next, I have provided the link to the data and
analysis completed during the project.
CONTENT EU: For any acid HA, the relationship between the pKa, the concentrations existing at equilibrium, and the solution pH is given by: pH = pKa + log [A-]/[HA] (see EU source) Acid / Base Equilibria Problems (Concepts: Acid / Base Equilibria, Henderson-Hasselbalch) CHEM504 After presenting my misconceptions
at the board (see baseline evidence), I met with several members of my
cohort in a small group. We talked about the concepts involved
and came up with a couple of different strategies for solving the
problem. Below, readers will see the correct solution to the
original problem, which is included in the image.
Problem with conceptually accurate solution
 CONTENT EU: Atoms obey the laws of quantum mechanics and have energy levels- Vibrational Energy (see EU source) Vibrational Modes of Carbon Dioxide (Concepts: Vibrational modes, bending/stretching, IR spectroscopy) CHEM507 After participating in a POGIL,
discussion, and related assignment, I learned about vibrational modes,
the difference between bending/stretching,
and how to determine if a molecule is IR active. Below, readers
will see a question from a quiz in CHEM507. To preserve the
reliability of the assessment, only the question of interest is
shown. In addition, only the specific portion of the answer that
is correlated to the baseline evidence is shown. The remaining
portions of the quiz and the question have been removed.
Vibrational modes quiz question
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| REFLECTION |
| Since the start of the MCE
program, I have come to recognize computer modeling software as a
valuable tool for bridging the gap between experimental evidence and
chemical concepts. One particularly salient example of this for
me was the GAMESS problem set #1 completed in CHEM502. In this
situation, the software was actually used as a source of data to
analyze. As described in the evidence, the purpose of the
activity was to determine the energy of two structural isomers and the
transition state that connects them at the HF/3-21G level of
theory. This particular investigation, and others like it, are
"experiments" that cannot be physically carried out in the lab, so
computer applications like MacMolPlt and Chem3D are one of the only
sources of meaningful data. This technology is incredibly
valuable for theoretical chemists, particularly for predicting the
energy of transition states or theoretical reaction
intermediates. In addition to my experience with software as a
modeling tool and the computer programs themselves, I also gained some
valuable exposure to reaction coordinates. As shown in the
baseline evidence, my knowledge related to energy diagrams was somewhat
limited before the first summer of the program. However, it is
clear from the evidence of growth that my comprehension of related
energy concepts improved considerably. I have identified the
process as exothermic by calculating a loss of energy over the course
of the transition (-47.37701 kcal/mol). I have also incorporated
the idea of activation energy (energy barrier) and found it to be
60.36646 kcal/mol when going in the "forward" direction. Finally,
I shown my understanding of the transition state by including it within
the website and calculating its energy (-70940.06825). Acid/base chemistry was a sticking point for me all the way up until the last summer. In fact, I recall identifying related concepts on more than one "first-day inventory" as a weakness that I was hoping to improve. Finally, in CHEM504 I figured out one of my major difficulties. As shown in the baseline evidence, I was treating a weak acid as though it should completely dissociate. Looking back, this silly misconception ended up causing me a great deal of trouble. After conferencing with my cohort members I got everything straightened out, realizing that only strong acids and bases dissociate completely in solution. Weak acids and bases establish an equilibrium with their conjugate. To handle this situation, I got the hang of the ICE diagram method again, something that I haven't done since my undergraduate courses. This is the way that I successfully handled acid/base equilibria for the remainder of the course (and program). As shown in the evidence for growth, after coming up with expressions for the equilibrium concentration of nitrous acid and its conjugate base, I utilized the Henderson-Hasselbalch equation to determine the hydroxide ion concentration. From there, I was able to easily calculate the moles of hydroxide using the molarity and the volume. The first time I studied the theory behind IR spectroscopy my head was spinning because of the complexity. Since I lacked much of the foundational math, it was really out of my league. This is illustrated in the baseline evidence, where I was unable to come up with anything meaningful in my "preview" quiz question. Fortunately, CHEM507 offered a primarily qualitative treatment of the topic. Only the essential quantitative information was presented, which generally came in the form of easy-to-digest POGIL's and PIM's. In the beginning of the course, we learned about the basics by calculating center of mass and relating it to energy. Soon after we discussed the quantum nature of vibrational energy, by examining the possible "v" states in comparison to those that exist for other forms of energy (i.e. translational, rotational, electronic). Later, I learned the simple formulas for vibrational degrees of freedom for linear and non-linear molecules. As shown in the evidence for growth, I was able to apply the linear version (3N-5) to carbon dioxide to determine that it has four. In addition, I labeled them each as a bend or a stretch respectively. Finally, I determined if each was IR active by considering if an oscillating dipole is present. In the case of the first, the stretch is symmetric and so it doesn't not result in an oscillating dipole. It will not be IR active. The others, the asymmetric stretch and the two bends, will be IR active. |
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