Assignments

Assignment Page

All of the assignments given during the program are listed and explained below. Links to the actual assignments and the peer review main page are included.

Assignment 1: Your Personal Molecule

The goal of this assignment was to introduce the students to a molecule that that they would deal with for the rest of the course and to teach them how to determine the molecular formula, count units of unsaturation, and draw isomers. To begin thinking about the three dimensional structure of the two dimensional molecular line drawings, the students were required to make their molecule from a molecular model kit.

For this assignment, the students were given a handout (link below) which listed 15 biologically interesting molecules (one for each student) with a reference of a journal article which contained the molecule of interest. Some of the journal articles gave general structures or did not specifically name the structure assiociate with the molecule, so some of the references on the handout I gave have a clarification. The students were required to go to the referenced article in the undergraduate library, copy the title page and the page where the molecule appears, and complete the assignment related to their personal molecule. The students would return to their molecule in later assignments.

The Assignment 1.

The Peer Review Sheet for Assignment 1.

Reflection (from JKP: 07/20/98)

Before the class started, I was concerned that this assignment may be too much for the students. After some additional help the evening of the first contact, I found my concern to be unfounded. The students were able to complete the assignment with minimal assistance from me.

I would make several changes to the assignment. I would choose molecules that were more similar in atom count. There was too large of a range in the size of the molecules, making some students work a lot harder than others. I would prefer if all the molecules were of similar atom count.
I would also like to find references that had the complete structure clearly drawn and identified so that I did not have to give clarifying directions for the students to find the molecule or "build" the molecule by specifying groups from a general structure. This was an added aspect that complicated some of the students' molecules. Finally, since this was a dental course, I would have preferred to find more molecules with dental application. In the interest of time, I settled on the ones I gave the students. The main criteria that I used was that they students would be able to show several resonance structures.

Assignment 2: Isomerism and Arrows

This assignment was designed as a follow-up on the isomerism issue and as an introduction to mechanistic arrows. Six problems were included which showed a connectivity change giving an isomer and one problem showed a connectivity change resulting in the liberation of carbon dioxide. Various question designs were used. Some questions gave a starting structure with mechanistic arrows, and it asked for the resulting structure. Some questions gave a starting structure with arrows, asked for the resulting structure, then gave another structure and asked for the arrows which would cause the final structure. Finally, one questions gave the starting and final structure and asked for the mechanistic arrows.

The Assignment 2.

The Peer Review Sheet for Assignment 2.

Reflection (from JKP: 07/20/98)

This was an excellent assignment with the exception of the organization. The questions should be organized in the order of difficulty with the easiest question at the beginning. The first question given on this assignment is one of the most difficult to complete, and I found that it was too early in their learning for them to complete it well. The last question, in my opinion, is also very difficult, and this question was done correctly by many more of the students than completed the first question, and without any assistance by me. This speaks greatly for organizing the worksheet in the order of difficulty so that they are better prepared to complete the harder questions by exposure to easier questions first.

Assignment 3: Practice on Properties

This assignment was designed with the intention of increasing the students' understanding of physical properties. It was designed by asking for rankings in melting point, boiling point, solubility in water, and dipole moment. There were various ranges of molecules in each section (with some repeated between the melting point section and the boiling point section). The molecules were chosen to illustrate how branching, surface area, and spherical structures affect melting and boiling point, how hydrogen bonding acceptor and donator groups contribute to solubility in water, and how electronegativity affects dipole moment.

In addition to the properties worksheet, the students also had to draw their personal molecule from Assignment 1 in ChemDraw with a generic name (other than the real name) and bring the file on disk to the next session to be compiled into a single sheet by the instructor.

The Assignment 3.

The Peer Review Sheet for Assignment 3.

Reflection (from JKP: 07/20/98)

If I had to re-design this worksheet, I would ask for a simple explanation of the rankings. Although I did not observe this, it would be easy for the students to just write numbers for the ranking and not think about the reasoning at all. I would eliminate number 5 under boiling point because it is difficult to rationalize trends with hydrogen fluoride. I would eliminate number 4 under melting point because the differences in stacking ability are not that clear between these molecules. In number 5 under solubility in water, I would replace hydrogen fluoride with propanol or another alcohol as this would make the factors affecting solubility clearer. Finally, I would eliminate number 2 under ranking dipole moment because it pertains to geometry and the cancelling of dipole moments which was not something we had covered in class yet.

Assignment 4: Structure and Resonance

The students had already created personal names for their molecules. In this assignment, the question of representationalism is addressed. The handout contains line drawings of the molecules along with the student names. There is also a link to the copy of the web site that I created, on which the space-filling models of the molecules resided with pulldown menus of names. Students needed to go to the web site and see if they could relate the space-filling representation to the line drawing. This assignment was designed to teach the students something about their personal molecules. It also had the intent to further introduce the students to the three dimensional structures of molecules and to reinforce that the two dimensional line drawings are merely a representation of a real life thing. The students were also required to draw three resonance structures and to rank their relative contributions.

The Assignment 4.

The Peer Review Sheet for Assignment 4.

Reflection (from JKP: 07/20/98)

The web assignment went very well. All the responses receieved from the students were completely correct. I was very impressed by the students' ability to complete this assignment. The students seemed to like the assignment and the connection of the 2-dimensional structures to the 3-dimensional shapes. They liked seeing what their molecules really look like. Some students had trouble initially understanding what was expected of them on the webpage. One student thought that only their molecule needed to be identified from the page. Perhaps more explicit directions are needed.

There were a lot of problems with the resonance assignment. I believe that more in-class examples are needed prior to this assignment. Even though most of the assignments were incorrect, it still served as a learning experience.

Assignment 5: Practice on Shape

The goal of this assignment was to give the students practice determining molecular geometry as derived from the hybridization model. Hybridizations were not specifically asked for in the assignment, but it was presented as a method for determining geometry in the previous class.

The Assignment 5.

The Peer Review Sheet for Assignment 5.

Reflection (from JKP: 07/20/98)

I would not change anything on this assignment except for number 2. This is a salt, which added an aspect of difficulty. Even more significant than that was the NO₃^- molecule. This is a very difficult structure to determine, and I should not have included it in this assignment.

Assignment 6: Acid/Base Worksheet 1

This assignment was designed to introduce students to protonation/deprotonation issues.The students were required to give ALL the possible deprotonation product of the given molecule in the first section and ALL the possible protonation products of the given molecule in the second section. Inadvertently, this assignment also introduced students to the issue of symmetry within molecules.

The Assignment 6.

The Peer Review Sheet for Assignment 6.

Reflection (from JKP: 07/20/98)

This assignment was a great introduction to acid/base chemistry with the protonation and deprotonation sections. Some students only drew one possible product for each problem, not realizing that the assignment was asking for ALL the possible products. There are also interesting symmetry issues that arise with this assignment. The students readily accepted that two hydrogens on a methylene are identical and that three hydrogens on a methyl group are identical, but only after I showed them the rotation with a model. The symmetry with the ring in Part 1. a) was a little more difficult for the students to grasp, especially since there are two planes of symmetry. There was also some difficulty with Part 1. h). Most students understood that the three hydrogens on each methyl were equivalent, but then it took quite a bit of discussion as well as demonstration with a model of (CH₃)₃S⁺ before they really understood. I encouraged the students to make models of each molecule to identify which protons were actually the same, but perhaps this should be an explicit direction.

Assignment 7: Acid/Base Worksheet 2

The goal of this assignment was to introduce the students to reactions. The students were required to predict the products of the acid/base reactions and to add the mechanistic arrows. The second part of the assignment was designed to test the students' understanding of acidity and basicity by ranking molecules.

The Assignment 7.

The Peer Review Sheet for Assignment 7.

Reflection (from JKP: 07/20/98)

Overall, the students did extremely well predicting the products of the reactions. I was a bit concerned when I handed out the assignment because I feared that they may not know what to do, but they really surprised me in a good way! When ranking acidity and basicity, some students became confused with what factors they were considering. Some students were able to rank the molecules correctly, but didn't fully understand their own thought process. It helped when I discussed Part 3. a). I drew the molecules in a row on the board and drew an arrow pointing down from each one. Then I drew the product of the deprotonation. I explained how one way to rationalize the trend was to look at the stability of the product, and to rank that based on electronegativity of the atom with the negative charge. After this example, I went over an example ranking the strength as a base. The students understood the rankings much better after these discussions.

Assignment 8: Acid/Base Worksheet 3

This assignment was designed to test students' understanding of acidity and basicity by requiring them to predict the products in several reactions and to add mechanistic arrows explaining the reaction. Then they were asked to determine the direction of the equilibrium based on pKa values. There were many levels of understanding that were tested here.

The Assignment 8.

The Peer Review Sheet for Assignment 8.

Reflection (from JKP: 07/20/98)

The students said that this assignment was hard. Some had trouble predicting the products in a few of the reactions. There was some trouble with molecules like KOH and especially NaHCO₃. It made A LOT more sense to the students when I drew Na⁺ HCO₃^- on the board and told the students just to think of those molecules as negative ions and not worry about drawing the structure (for HCO₃^-). The various levels of understanding (predicting products, using mechanistic arrows, using the pKa table, understanding pKa significance) that were needed to complete the entire assignment were one of the most valuable aspects of this assignment.

Before giving the students the assignment, I told them to think about everything in the terms of acidity. I did this so that the students would not look up the pKa values of the bases in the reactions and predict the equilibrium that way. My reasoning was that if I discussed something in class and if students discussed issues with each other, I wanted them to all be thinking about pKa in the same terms. It has been my experience that students can become easily confused when dealing with issues of acidity and basicity, and this direction helped to keep students on the same track.