Spiral Study

Reprinted from Journal of Chemical Education, Vol. 72, Page 530-532, April 1995.

the copyright owner.

A Novel Spiral Approach to Introductory Chemistry Using Case Studies of Chemistry in the Real World

Christina P. Brink, David E. Goodney, Norman J. Hudak, and Todd P. Silverstein

Willamette University, Salem, OR 97301

In an effort to respond to the many concerns regarding the general chemistry sequence, several members of our chemistry department spent the last four years reviewing our current curriculum, planning major revisions in our introductory course, and developing the written materials for a new curriculum. The revisions were implemented for the first time during the 1993-1994 academic year. We have attempted to address the problems of the general chemistry curriculum by developing a two-course sequence that uses the first semester to introduce qualitative discussions of most chemical concepts, from structure and bonding to kinetics and chemical equilibrium. Students who drop after this course get a well-rounded introduction to the methods and concerns of chemistry. Furthermore, exceptionally well-prepared high school students should more easily place out of this course and start with the second-semester course. The second-semester course then spirals back through the same chemical concepts in a more rigorous and quantitative way.

The second spiral explores fundamental chemical ideas in a framework of real-world case studies such as lasers, air pollution, and blood chemistry. Each case study builds on chemical knowledge from the first semester, but then it explores the concepts in greater depth and with greater mathematical sophistication. This approach allows students to appreciate the concept's application in a rigorous and non-superficial manner.

When we listed the topics we wanted to survey in the first semester, it was apparent that no suitable textbook existed. We briefly considered preparing a detailed list of sections and even paragraphs from a standard text for students to read, in effect, a road map through the text. We quickly rejected that idea as unsatisfactory and confusing for students. Our best alternative was to cut and paste an existing textbook. With the publisher's and author's permission, we chose to modify Kotz and Purcell's Chemistry and Chemical Reactivity, second edition. We took apart the Kotz and Purcell text, then reassembled it, along with some of our original text, into a manuscript for the students. This manuscript refers students back to color photos, some tables, and figures in the original text rather than reproducing them. Students buy both the manuscript and the original text. While all of the reading assignments come from the manuscript, students may use the text's figures and tables as needed. This method has the advantage of preserving copyright privileges of the authors and publisher while providing a manuscript tailored to the needs of this particular course. For the second semester, students simply purchase a separate Case Study manuscript. We have dubbed this new year-long curriculum the spiral-case study approach.

First Semester: Qualitative Survey

Topics covered in the 1st semester of the spiral approach to Introductory Chemistry are listed below.

1. The Tools of Chemistry
Scientific Method
Units and Measurement
Significant Figures
Energy

2. The Stuff of Chemistry
Density, Classification of Matter
Atomic Theory and Structure
Introduction to the Periodic Table
Ions, Ionic compounds
Compounds Naming
The Mole
Molecular formulas, Molar mass

3. Chemical Reactions
Balancing equations
Stoichiometry
Solubility
Acids and Bases
Redox Reactions
Net Ionic equations
Common Chemical Reactions
Common Organic Functional Groups

4. Structure and Bonding
Periodic Trends in Properties
Bonding and Polarity
Molecular Shape and Polarity
More Organic Functional Groups

5. Chemical Dynamics
Equilibrium
Energy and Spontaneity
Equilibrium Constant
Thermodynamics versus Time
Electrochemistry
Kinetics: Reaction Rate
Rate Laws

6. Phases of Matter
Gases: The Ideal Gas Law
Kinetic Molecular Theory
Liquids
Intermolecular Forces
Solids
Phases Changes
Phase Diagrams
Solutions

Notice that Chapters 1 and 2 resemble the conventional course fairly closely, except that limiting reactant calculations and composition by mass (empirical formulas) have been omitted. (These are introduced in laboratory experiments, as well as in the second semester). In Chapter 3 we omit balancing complex redox reactions and add brief discussions of organic and bio-organic compounds. In Chapter 4 we omit all discussion of electromagnetic radiation, particle-wave duality, the Bohr atom, and atomic and molecular orbitals. This allows us in Chapter 5 to include a complete overview of thermodynamics (including Keq, D H° , D S° , D G° , but omitting calorimetry), as well as kinetics and electrochemistry.

While this may seem like too much to cover in a single semester, removing complex material like empirical formulas, orbitals, and redox equation balancing, does, in fact, leave enough time for clear qualitative discussions of the included material in class. Students found the course neither easier nor more difficult than the old Introductory Chemistry I. While it involves fewer calculations and less physical theory, it covers a broader array of topics. This course lays the groundwork for detailed examination of the chemistry involved in the case studies of important environmental and biological problems.

Second Semester: Case Studies

A case study is a practical example or set of phenomena within which many fundamental concepts of chemistry may be integrated and applied. Our case studies include lasers, fossil fuels, air pollution, blood chemistry, marine chemistry, and ozone, among others. Our case studies are keyed to the same Kotz and Purcell text used in the first-semester course. We rely on the textbook to provide the detailed chemical theories and mathematical rigor as well as some practice problems and exercises. By relying on the textbook, we are able to keep our case studies generic. We have considered re-writing them to incorporate the detailed chemical theories. However, the advantage of keeping them generic include :

The case studies can be used with any existing textbook.
The case studies can be kept shorter because the explanatory material covering the theories is omitted.
The flow of the case study is not interrupted with detailed general chemical theory.
When, in later case studies, we use the same chemical principles again, we can refer to the text rather than to the previous case study.

For our particular course, we began with eight case studies which focus on the listed chemical principles.

1. Lasers
quantized atomic and molecular energy levels
light and energy
absorption and emission of light

2. Graphite, Diamond, and Buckyballs
Periodic Table
electron configuration
orbitals, hybridization, bonding

3. Fossil Fuels
molecular structures
energetics, D H, D H° f, D G
Hess' Law, bond energies

4. Air Pollution
gas laws
kinetics
reaction mechanisms

5. Ozone
structure
Valence Bond Theory
Molecular Orbital Theory
free radical reactions

6. Marine Chemistry
Concentration
Colligative properties
Solubility and Ksp

7. Blood
chemical equilibrium
weak acids and bases
buffers

8. Bioenergetics
Redox reactions
Electrochem cell reactions
E° , D G° , and Ksp

As an example of how we developed the case studies, let us consider in more detail the Bioenergetics cases study. What kinds of questions are raised?

How do plants store energy in food?
How do we get energy out of food?
How much do foods differ in energy?

What are the concepts necessary to answer the questions?

D Hreact
Bond energies
Electrochemistry: balancing half-reactions
D E° , D G° , and Ksp
Nernst equation

A brief topical outline of Bioenergetics:

I. Introduction

A. Examples of respiration: oxidative releases energy
B. Photosynthesis: carbon reduction driven by light energy
- II. Half-reactions and Cell Reactions
A. Balancing in aqueous solution
B. Review of E°
1. E° cell from tables
2. Spontaneous versus non-spontaneous redox reactions
3. D G° and Ksp
A. Nernst Equation

III. Bioenergetnics

A. Balance Respiration Reactions (Half-reaction Method)
B. Glucose Metabolism
1. Photosynthesis
2. Respiration
Calculate Energy Available
1. E° cell
2. D G°
3. Spontaneity
4. D H° calculation for fat oxidation
A. Real-Life Conditions: non-standard state calculations

One clear advantage of the case study approach is the way in which ideas are reiterated as we progress from one case study to another. For example, energy levels in atoms and molecules are introduced in the Laser case study. In the Graphite, Diamond, and Buckyball case study, atomic orbitals and various bonding methods are introduced that more clearly illustrate specific kinds of atomic energy levels and their characteristics. Finally, in the Ozone case study, molecular energy levels and their relationship to atomic energy levels are discussed. At this point, lasers can be revisited briefly so that the general energy levels inherent in the laser source can be more specifically addressed as molecular or atomic energy levels. The Fossil Fuel case study emphasizes thermodynamics and Hess' Law. Though the emphasis in the Air Pollution case study is kinetics, thermodynamic concepts are repeated and applied as we look at the formation of various nitrogen oxide pollutants. The Air Pollution case study also provides many opportunities to stress the very important dynamic between kinetics and thermodynamics.

We have found that case studies can be used fruitfully to teach specific, fundamental chemical concepts. Another feature of using the case study approach is that different courses could be based on different combinations of topics. Thus, our goal is not to provide one set of case studies that everyone must use; rather, our approach allows for a wide variety of topics to be developed so that a particular institution can choose a set that best suits its needs.

Student Reactions

Student reaction to the new introductory chemistry curriculum in general and to the case study approach in particular has been very favor-able. Interestingly, in response to a series of survey questions, each of the case studies was mentioned as a favorite and also as one that could be discarded. Although there was no clear winner, the Air Pollution study was often cited as most important. Students often were reluctant to choose one to discard. We also were gratified to read the responses to questions regarding whether or not the new approach met its goals. Students perceptively recognized those aspects of the course that we had hoped would be the advantages of a spiral-case study approach. They commented positively about such things as building on the first semester, applying the same concepts to several different cases studies, and anticipating future applications of ideas in other case studies.

Conclusions

Our experience suggests that the case study approach is a viable option for teaching chemical principles and applications when preceded by a more qualitative and general introduction to the field. Furthermore, students respond very positively to the case study approach and appear to like it better than the traditional introductory chemistry sequence.

In order for our approach to be adopted widely, the case studies that we have prepared specifically for Willamette would need to be augmented with additional topics so that other institutions could select those that meet their curricular demands. We have found that though a considerable amount of thought and effort goes into preparing the case studies, bringing them into the classroom is relatively straightforward. We are still considering whether to keep our case study materials generic so that they can be keyed to any introductory textbook or re-writing them to incorporate the theoretical concepts directly into each study. We are currently discussing various possibilities with textbook publishers.

Acknowledgment

Support was received from Atkinson, Hewlet, and National Science Foundations.

Letters

Chemical Engineering News. 14 August 1995.

Volume 73(33), pp. 2-3.

Another innovative curriculum

We read with interest the article about the National Science Foundation’s (NSF) $11 million program, "Systemic Changes in the Undergraduate Chemistry Curriculum" (C&EN, May 29, page 7), in which four groups involving some 50 institutions "will begin a five-year effort at curriculum development, evaluation, and dissemination." In particular, two groups headed by Beloit College and the University of California, Berkeley, will receive a total of $4.6 million to "develop complementary sets of modular course materials, each focusing on real-world problems. The modules will introduce core concepts, show links between chemistry and other disciplines, and create a flexible model for curriculum reform."

These are important goals, and this type of new approach to teaching chemistry has been advocated vigorously over the past decade. Thus, we certainly appreciate NSF's willingness to fund these large, substantial programs. Nonetheless, we would like to point out that, at least as far as the introductory chemistry course sequence is concerned, we have already developed this type of new course and have been teaching it for two years now. Student response has been overwhelmingly favorable.

We developed the course sequence, which we have dubbed a "spiral/case study approach," between 1990 and 1993 with only $44,000 of NSF support plus some internal Willamette University funding. We have reported on our progress at three of the past four ACS national meetings and have published descriptions of the course sequence [CUR Quarterly, 14, 127 (March 1994); J. Chem. Ed. (in press)].

Briefly, we rearrange material so that during the first semester we cover all of the major topics in general chemistry (for example, aqueous reactions, gases, atomic structure and bonding, thermodynamics, and kinetics). We accomplish this feat by taking a fairly qualitative approach to the material, avoiding intricate calculations and theory wherever possible.

During the second semester, we revisit major topics within the context of case studies that have direct real-world implications. For instance, our case study on air pollution revisits kinetics and gas laws; the case study on blood chemistry revisits acid/base chemistry; and the case study on fossil fuels revisits stoichiometry and yield, bonding, and thermodynamics.

We developed a series of laboratories to complement each semester's material. For the first semester, we adapted most of the experiments from labs published recently in the Journal of Chemical Education. For the second semester, we devised a series of laboratory case studies that involve teams of students doing extended, fairly independent projects that last from two to four weeks. All of the labs engender significant exposure to sophisticated instrumentation such as spectrophotometers, Fourier-transform infrared equipment, gas chromatographs, and more.

The course sequence we have devised comes very close to meeting the needs of all of the students enrolled. The 30 to 40% of students who take only the first semester of the course sequence get a complete, qualitative picture of modern chemistry, rather than a detailed picture of only half of the field. The students who go on to finish the second semester get to see concepts and theories from the first semester applied to important real-world problems like acid rain, the ozone hole, and fossil fuel burning.

We have had excellent student responses to the new courses, especially the case studies. Student evaluations have been enthusiastically positive, and student retention of material has been more than double that found in past studies (68% versus 30%). Performance on the standard ACS exam is generally better than average (final results will be available soon). We are currently exploring various textbook publication options for our course materials.

In closing then, we would like to alert readers that there are alternative models to the current chemical education paradigm already up and running. Our spiral approach is effective, powerful, and popular with students. Those interested in further information about this program may contact us directly by fax (503) 375-5425 or email: tsilvers@willamette.edu.

Todd Silverstein
Christina P. Brink
David E. Goodney
Norman J. Hudak
Chemistry Department
Willamette University
Salem, Ore.