General Chemistry Assignments

Introduction


Completing traditional end-of-chapter homework assigned in organic chemistry courses is vital to developing students’ ability to demonstrate that they can solve the problems of organic chemistry. They need to be able to master the outcomes: put together reasonable structures, represent them in a variety of pictorial forms, name compounds, identify functional groups, correlate reactivity with those functional groups, predict products of reactions, identify stereochemistry, predict stereochemical changes that accompany reactions, draw mechanisms, and plan syntheses.(1) But traditional homework ignores the underlying issue of understanding how and why we make these representations the way we do, and fails to delve deeply into the language of organic chemistry. It treats the core thoughts, the essential underlying understanding behind the exercises, implicitly. Conceptual understanding of topics within organic chemistry is very important for success in the course.(2) The exercises proposed below are designed to improve students’ conceptual understanding, complementing end-of-chapter homework.

A further challenge for chemistry students at all levels is accepting that the responsibility for learning lies with themselves. No matter how good the instruction, unless the student is constructing her own thought process, she will not learn satisfactorily.(3) While there are methods that teach metacognitive strategies directly,(4) these exercises do so indirectly. The exercises described herein are designed to help students reinforce previous knowledge as they build on concepts from prerequisite courses, and then progress to building new knowledge and concepts within the framework of course material. The assignments are designed to create active, critical readers using the ideas pioneered by Paul and Elder.(5) The students must pull apart the text they are reading into its constituent knowledge types, rather than just try to understand it.

Writing assignments are nothing new in chemistry courses. There are general studies courses designed around understanding chemistry through reading and writing,(6) or graduate courses designed to teach scientific review.(7) Calibrated peer review (CPR) is a process that challenges students to write essays on chemistry topics, and then students are trained to review other students’ essays.(8) There are other assignments available in the writing-to-learn category where students write an essay on an organic chemistry topic.(9) In a more unique approach, Wilson(10) challenges students to teach others about topics within organic chemistry.

I have adopted two types of homework assignments, listed in the syllabus as Journaling Assignments, to address the underlying thought processes of organic chemistry that traditional end-of-chapter problems leave unexamined. Over the past seven years students in my Organic Chemistry I course have completed these assignments in addition to the end-of-chapter questions to supplement their deeper understanding of organic chemistry. I would argue these assignments not only induce students to think more like practiced organic chemists, but develop in students better critical reading skills that should be applicable in whatever field they choose.

Assignments


Two types of assignments are discussed: Nosich’s SEE-I(11) (state, elaborate, exemplify, and illustrate) and Text Analysis, modeled after Paul and Elder.(5a) The SEE-I assignments are designed to help students think more deeply about individual concepts. The Text Analysis assignments are designed to help students read their textbook more critically and to guide students to think about the information in their textbook in terms of the type of knowledge that is communicated. A positive aspect of these assignments is that any topic that needs emphasis to the students could be adapted easily to one or the other assignment type.

In the SEE-I assignment, the statement needs to be clear and concise, but should be a complete definition. Elaboration can expand upon the definition in many ways. Often even a clear definition leaves some room for interpretation; the elaboration should complete and expand the definition. If technical terms were used in the original statement, those could be defined as well. The example should be a concrete example, often with chemical species. Many students will include an image in their assignment as part of the example. The illustration is the part that truly challenges the student to think deeply about the topic. The illustration should be an analogous explanation that uses no chemical terms. This is a miniature creative writing assignment. The student is challenged to explain the concept as if to a person with no background in chemistry. This requires the student to write creatively about the topic, which facilitates deeper thinking about the subject.

SEE-I Example
The SEE-I assignment focuses on discrete concepts. The SEE-I topics used in my class are orbital, resonance forms, electrophile and nucleophile, enantiomer and diastereomer, reaction energy diagram, SN2, and tautomers, as shown in the following example.
  • Statement: A molar equivalent is a ratio of two substances that have the same number of particles.

  • Elaboration: Reactions that occur in a 1:1 ratio require equal numbers of particles to react completely, not equal masses. The molar equivalent gives an equal number of particles by taking into account the different masses of the particles involved.

  • Example: 6 g of carbon-12 has the same number of particles as 10 g of neon-20.

  • Illustration: There is a jar of quarters that I can win if I can guess the correct number of quarters. If I measure the weight of the jar, I can use my phone to look up the weight of one quarter and guess the number quite accurately.

Text Analysis Overview

Text Analysis assignments are critical reading assignments, requiring that the students read a section of the textbook analytically and categorize the knowledge. The goal of this exercise is to get students to think about all the different types of knowledge that are being passed on to them in their text. This in turn should allow the student to better assimiliate accepted knowledge and be able to develop healthy skepticism about the topics. Not all classifications are necessary for all sections, so a subset is usually assigned to focus the students on the most useful parts of the topic.

The text is categorized according to the following classifications:
  • Purpose: Why was the section written?

  • Information: What data or facts are included in the section to support the argument/explanation? Ideally these would be experimental observables.

  • Assumptions: What goes unstated in the reading, but is essential for understanding and/or accuracy?

  • Clarity: How clear is the author’s presentation? How could it be clearer?

  • Concepts: List and give a brief definition of the ideas and terms that are specific to organic chemistry and necessary for understanding the topic.

  • Conclusions: These should be the author’s conclusions, not yours.

  • Implications and consequences: How will the information in this section affect or influence other topics covered in the text? What are the organic chemistry implications and consequences?

Hybridization Text Analysis Example
The Text Analysis topics are hybridization, substituted cyclohexanes, E2 stereochemistry, carbocation rearrangement, Markovnikov’s rule, acetylide anion reactions, and hydrogenation of alkenes and their stability.(12)
  • Purpose: To give a thorough explanation of why organic chemists use hybridization of orbitals of differing angular momentum to describe typical bonding within organic molecules.

  • Assumptions: Basic information about the filling of orbitals for the ground state, and what orbitals are (and are not).

  • Concepts: Major concept: An orbital is a statistical description of electron location. Other concepts: Energy levels are one type of organization of orbitals. Molecular geometry is a three-dimensional relationship of atoms. Ground state is the lowest energy electron configuration. Valence shell is the outermost shell of electrons. Bonding is the interactions of atoms that holds together molecules.

  • Conclusions: Each bond in CH4 is formed by the overlap of an sp3 hybrid orbital of carbon with a 1s orbital of hydrogen. These four bonds point to the corners of a tetrahedron. By using hybrid orbitals, the shape of the molecule and the shape of the orbitals comprise the molecule match, resulting in better bonding.

  • Implications and consequences: This further explains that bond angles are dependent on the number of “groups”; it will be useful when we look at molecular shape and reactivity of molecules that are more complexly bonded.

Substituted Cyclohexanes Text Analysis Example
  • Information: Two chair conformations of methyl cyclohexane are shown. In the graphic it is indicated that the conformation with the methyl equatorial comprises 95% of the mixture, while the axial methyl conformation is only 5%. It is stated that this correlates to an energy difference of 7.6 kJ/mol. In the case of cis-1,4-dimethylcyclohexane, the two chair conformations are represented as a 50%–50% mixture, which shows that these two conformations are equally stable.

  • Concepts: The chair conformation is used to visualize the conformation of the ring, like a deck chair. Axial (along the axis) and equatorial (around the perimeter) are used to demonstrate the relative position of the groups on the chair. The ring-flip describes the change from one chair conformation to the other. The concepts of cis (on the same side of the ring) and trans (on opposite sides of the ring) are reviewed.

  • Conclusions: Conformational preferences of substituted cyclohexanes are determined by energy. The lower energy chair conformation is preferred.

  • Implications and consequences: Reactivity of substituted cyclohexanes can be strongly influenced by conformational preferences. If the conformation required for a reaction is disfavored, that reaction can be considerable slower.

Evaluation of Student Work


The Journaling Assignments are valued at 10 points each. I assign approximately one per week, for a total of 14, just before subjects are covered in class. The rest of the points for the course (800 total) come from in-class quizzes, tests, and the comprehensive final. Initially I assigned the Journaling Assignments just after I covered the topic. I moved them to just before I covered the topic in the lecture to encourage the students to read the text before coming to lecture. I encourage the students to keep their responses succinct for two reasons. First, with a typical course size of 36, the grading load is more manageable. Second, I want the students to think carefully about the assignment, not reproduce everything in that section of the textbook in the hope that they include what I want.

Evaluation of student work for the SEE-I assignment is straightforward. The statement, elaboration, and example sections can be paraphrased from the textbook or the Internet. The statement needs to be a clear definition that is specific enough to define the assigned concept. Many students will leave their statement very vague so they can use the elaboration section to complete the statement. This is not satisfactory. The elaboration needs to be more in-depth. Better answers use technical terms in their definition, and then define those terms in the elaboration. Good elaboration digs a little deeper. The example is required to be a specific example. Generic representations like Nu for nucleophile or X for leaving group are not acceptable. I encourage them to use specific ions or elements because the generic nature of the concept has been addressed in the statement and elaboration.

The illustration is the most challenging portion of the assignment, and the part that gives the most indication of student understanding of the topic. As many educators have experienced, trying to describe a topic without technical terms stretches the educator’s understanding of the topic as well as the learner’s understanding. Many of these analogies are shallow or only address one layer of the topic covered, but the better ones can represent several aspects of the concept.

For the Text Analysis assignments, the students often struggle early to discern how to break down the text to the components requested. Training students to think about categorization of the knowledge presented to them is the primary purpose of these assignments. Most students can satisfactorily identify the Purpose and the Conclusions in their first assignment. Occasionally, students will get stuck on the last statement in the section from the author rather than finding the overall conclusion. Students can most often identify some of the concepts, and it is fine if it is a small subset of the concepts in the section.

In the initial assignments containing the Information section, which is defined as experimental data (see above), most students summarize the whole section. In feedback, I focus students on identifying the outcome of the experiment upon which everything else is built. Often there is scant experimental evidence presented. This provides a challenge to students to thoroughly search the text to determine what experiments were performed.

Many students are unmotivated when writing the Implications and Consequences section, and merely state “this knowledge will help me understand future knowledge”. I require that they are much more specific, linking this topic to other topics we have covered or preferably looking forward to see what other topics will be built upon this one.

Student submissions improve throughout the semester (see the Supporting Information for examples). Initially many students require direction on developing an analogous description for SEE-I or struggle with proper categorization of knowledge. For example, students very frequently will label concepts (word pictures that help us understand a topic) as information (data derived from an experiment). By the end of the semester, students are much more capable of recognizing the types of knowledge for what they are; that is, they are better critical readers.

Student Feedback and Analysis


In an effort to improve the Journaling Assignments when first offered, I surveyed the students with two questions. The first question (see the Supporting Information) asked the students to rate the helpfulness of the assignments. Generally, the students found them to be helpful.

The second question was open ended: “Give any suggestions you may have for improving the journaling assignments.” All responses are included in the Supporting Information. Student responses selected to show the primary utility of the assignments are below:

Hmm, I think the only thing would be to maybe do more of the ones where we read a section and then have to write an introduction, implications/consequences, and a conclusion. I like those the most because it made you read and reread the section it was over and when you got done it made you feel much more comfortable with the information.

It forces you to read the book and describe subjects in depth.

Not only did it help me to learn the concepts assigned, but it also forced me to read other sections to further elaborate.

The journaling assignments helped out quite a bit. They made me reread and analyze the sections that were a little more difficult to understand. Perhaps more explanation over guidelines.

The common theme in these responses, and many others, was that the Journaling Assignments made the students “actually” read the text. I was honestly surprised with the number of such responses. I had assumed students in organic chemistry, a content-heavy subject, were at least reading the portions of the textbook that described difficult subject matter from lectures, or reading the portions necessary to complete homework assignments. So if nothing else is accomplished, the students should have a better understanding of the topics covered because they read the material. One student even goes so far as to suggest that I give more Text Analysis assignments because studying the material in depth with these guidelines made him/her more comfortable with the material. I try to emphasize to the students that they do not need additional assignments to break down the text, but that reading critically would increase their understanding of any text.

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