Chemistry for Everyone edited by
Interdisciplinary Connections
Mark Alber
Color Science, a Course for Nonscience Majors
Friends Academy Duck Pond Road Locust Valley, NY 11560
Maria C. Gelabert Department of Chemistry and Physics, Wagner College, Staten Island, NY 10310;
[email protected] Based on a course offered at the Fashion Institute of Technology (1, 2), a chemistry course entitled Color Science has been developed for nonscience majors at a primarily undergraduate college. Highly interdisciplinary, the science of color has applications in many fields. Within chemistry, this subject spans organic, industrial, solid state, coordination, and physical chemistry. Here, course development will be described in terms of balancing academic rigor and intellectual engagement to more favorably affect nonscience majors and address science literacy concerns (3). Student feedback, from course evaluations and midterm assessment data, was used to connect student perspectives with broader liberal arts goals involving learning by different methods, scientific content, quantitative literacy, and contextual understanding (4). In the sciences, there is much controversy over the distinction between courses for science and nonscience majors (5, 6). Recent literature on nonscience-major teaching methods suggests that a holistic approach bridging fields across the liberal arts would more effectively address the overarching issue of science literacy (7), currently considered low in the United States (8). Pedagogical literature focuses on making science classes more engaging and relevant (9, 10) to promote effective learning. The first time Color Science was offered, course evaluations indicated a low degree of academic challenge, gathered from responses to questions about how much time was spent on the course outside of class. Driven partly by these evaluations, course changes from the first to second offering consisted of more in-depth chemistry content, broadened context with inclusion of a biography (11) for class discussion and writing, and addition of an anonymous, midterm assessment survey to gauge student perception of subject, depth, breadth, and rigor (12). With the course modifications, average course evaluation responses did not improve from the first to second offering. Increased academic challenge was found to be statistically significant by an independent samples t test on perceived course difficulty (2001: N = 23, mean 3.16, standard deviation = 0.76; 2003: N = 32, mean = 2.68, standard deviation = 0.80; of a scale of 1–5, with 1 indicating most difficult). Further, a semipartial correlation analysis, where variability in course difficulty was established as a control over both offerings, revealed that perceived course difficulty accounted for about 31% of the variability in instructor perception responses. The 2003 midterm assessment, although favorable overall, indicated high variability in response to inquiries about subject depth and breadth, suggesting broad student preferences that anecdotally parallel the formal course evaluation responses. Student feedback, from both course evaluations and midterm assessment, has been instrumental in providing awarewww.JCE.DivCHED.org
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ness of student perception. For further development, I complemented this feedback with broader college mission goals. Besides mastery of content, liberal arts academic goals that are most applicable to Color Science are proficiency in learning with different modes of inquiry, including practice of listening, writing, and oral communication skills, and competency in scientific reasoning and quantitative analysis (13). I have attempted to constructively balance student feedback with the standards of a liberal arts mission. Below, I outline and describe four elements for Color Science that may be found in any science course: method, subject, quantitative rigor, and context. Anyone seeking further details about this course is welcome to contact me. Method Teaching methods chosen for this course include lecture, instructor demonstrations, student classroom activities, and instructor–student discussion. Here, a variety is strived for in the effort to engage as many students as possible over the course. Lecture is used extensively in this course. Merits and drawbacks of conventional lecture have been discussed in depth (14–16). While endeavoring to be as animated and engaging as possible, I encourage students to contribute by including class participation in the final grade. As an educator, I feel that “straight-up” lecture, in addition to disseminating information efficiently, enables students to exercise their own flexibility in learning by different methods. In various professional venues, for example, they will be expected to learn from speakers. I believe that college students can be made more aware of their capability of adapting to whatever teaching methods, including lecture, are employed. Instructor demonstrations using light boxes, prisms, and filters are used to illustrate light dispersion into a rainbow and additive and subtractive color mixing. In one class activity, students use colored cards to generate negative afterimages as a prelude to complementary colors. To demonstrate sound wave interference, two students with similar voice ranges stand at opposite ends at the front of the classroom, choose a note and hold it. Other students walk slowly across the back of the room and listen carefully for constructive and destructive interference. Activities still in development are class visits to other parts of campus; for example, one of my art colleagues described complementary colors and color balance in paintings. Extensions to graphic design, theatre set design, lighting, and painting are in progress and would complement any future laboratory component. Mauve, a book about the discovery of the dye in 1856 (11), is used for discussion and the linking of color chemistry to the historical beginnings of industrial chemistry. For
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this, students practice reading comprehension, in-class discussion, writing, and extension of scientific knowledge beyond the laboratory. Subject As stated earlier, midterm assessment indicated variable preferences with regards to depth and breadth of course material. Therefore, a variety is strived for with regards to content: in-depth subjects are laced with plenty of broad perspectives and interesting trivia. An excellent resource is Nassau’s The Physics and Chemistry of Color (17). Although more appropriate for science majors, this book has great reference value. Required books are currently Rossotti’s Colour (18) and Garfield’s Mauve (11). Overheim and Wagner’s Light and Color (19), intended for the nonscience major, is a more physics-based textbook recommended for the course. Ball’s Bright Earth (20) contains a plethora of chemical and historical information about dyes and pigments. Since Color Science is offered as a chemistry course, it includes more chemistry than the physics-based course from which it was adapted. Carbon–carbon bonding and conjugation are introduced as a prelude to organic dyes, often highly conjugated and many containing aromatic rings (21). The color progression from benzene (single ring, colorless liquid) to naphthalene (two rings, colorless solid) to anthracene (three rings, colorless solid, violet fluorescence) to napthacene (four rings, orange solid) demonstrates that as conjugated molecules get larger, the absorption edges shift into the ultraviolet region of the spectrum, enabling emission of visible light. This progression is also seen in conjugated chain molecules such as carotene. Synthesis and purification of dye chemicals, a critical aspect of industrial production, is a topic explored in Mauve (11). The concept of a chemical recipe is emphasized with dyes (organic molecular substances) and pigments (usually inorganic extended structures). Paint binders such as encaustic wax, tempera, casein, fresco, watercolor, and oil all involve a set of ingredients specifically mixed, analogous to a chemical synthesis (22). Adhesion of dyes often relies on a mordant or salt solution that a substrate material is immersed in before dyeing. Interface chemistry between dyes (or pigments), mordants (or binders), and substrate can also be explored. Paints such as acrylics, enamels, and polyvinyl chloride contain polymers. Basic chemical bonding, learned previously with benzene and other conjugated molecules, can lead to understanding the process of polymerization. These three polymers are introduced chronologically along with historical caveats behind each technology (20). Many historically important pigments contain the same few elements. Copper, iron, and cobalt (among others) span a broad color palette found in insoluble “salts of the earth”. Lead and arsenic are also found in many pigments. Arsenic, found in “emerald green” (copper aceto-arsenate) pigment used in wallpaper, is thought to be responsible for Napoleon Bonaparte’s slow poisoning in St. Helena via a humid environment and formation of arsine (20). Lead paint has been used for a variety of applications; the carbonate salt (“lead white”) was the main white pigment in household paint well into the 20th century before replacement with zinc oxide and 1156
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eventually titanium dioxide (20). Toxicity of arsenic and lead introduce a safety aspect easily connected to modern environmental concerns. There is also much interesting dye and pigment trivia, of which a few are described: • Indian yellow pigment, made from cow urine, was exported from India until animal-cruelty legislation passed in the 1890s, after it was discovered that the cows were raised on a diet of mango leaves that consequently made them severely malnourished (20). • Indigo and Tyrian purple, dye molecules differing in structure by two bromine atoms, have completely different sources (21): indigo from a plant native to India and Tyrian purple from shellfish in Tyre. Hundreds of thousands of shellfish were needed to make 1 ounce of Tyrian purple and the scarcity thereby associated this color with wealth and royalty (20). • Woad, a plant native to Europe and Asia, produces a dye containing the indigo molecule. Extraction of the dye involved soaking in urine, exposure to sunlight, and foot trampling for a few days, a consuming and odorous process (20). I like to compare this procedure with historic grape fermentation via trampling to make wine.
Quantitative Rigor Practice of quantitative skills through mathematical formulas and graphing is appropriate for any physical science course. However, maintaining this rigor and keeping students engaged can be difficult, and the professor’s attitude can make a big difference in how students perceive their effort. Teaching as a facilitator, by attaching meaning to the rigor and emphasizing that the skills are valuable (even though they might not see this formula again), helps students understand its purpose. Handling conceptual information is also crucial for scientific literacy. Under the best of circumstances, students might discover their own potential for science, completing the course with improved skill in asking questions and overcoming fears about seeking information, armed with confidence that they draw on scientific thinking when needed for professional or personal endeavors. In Color Science, students are asked to master calculations, dimensional analysis, and graphical manipulations. Specific examples follow. Development of graphical skills is enabled through complementary mathematical relationships between spectra. When incident light reaches a sample, three things can occur: absorption, reflection, and transmission. Each of the processes has its own spectrum, characteristic of the material, that all add to give the incident spectrum. The mathematical adding manifests in the conceptual principles of the generation of color; namely, that whatever color does not absorb gets reflected. The spectra of two complementary colored lights add to give a uniform “white” spectrum, whereas an analogous filter combination would yield no light, or a “black” spectrum; the principles of additive and subtractive mixing are thereby established (23). A more sophisticated and quantitative mode of graphing occurs in the study of the conventional chromaticity diagram developed by the Commission Internationale de l’Eclairage (CIE) (23). Consisting of a curved ribbon containing the rain-
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bow colors connected by a straight line representing red-violet (purple and magenta), the “white point” is the centroid and all saturated colors are on the perimeter. Any color may be quantitatively described with three variables such as purity, brightness, and dominant wavelength, and converted to chromaticity coordinates for use with the CIE diagram. This can be used much like a phase diagram, where a line between any two points or the area within a triangle of three points spans the potential color gamut possible by mixing appropriate quantities of light from each point. With the electromagnetic spectrum, technologies used by different parts of it and algebraic relationships between energy, wavelength, and frequency are studied. To some nonscience majors, manipulation of the simple formula E = hc兾λ might as well be rocket science, which is all the more reason to emphasize it. Every little bit of math does a service by enlisting quantitative skill in the student, however rudimentary the formula may be perceived by scientists. Further, this and other mathematical relationships (such as the photoelectric effect) are fundamentally important laws governing the nature of light. Context Simon Garfield’s Mauve tells the story of Sir William Perkin, a British chemist who in 1856 serendipitously discovered mauve, the first dye based on aniline (11). At minimum, this book is a biography of Perkin, describing how mauve was mass-produced and marketed; however, from a historical and regional perspective, it is much more. Mauve was found from a distillate of coal-tar, the first in a group of dyes discovered through similar chemical techniques. Experimental aspects behind this discovery spawned research in explosives, perfume, photography, medicine, and plastics. The experimental problem of scaleup and production gives a glimpse into how industrial chemicals (such as pharmaceuticals) are synthesized. Differences in governmental commitment to basic research in Europe—notably United Kingdom, France, and Germany—are explored before and between the two world wars. This book is rich with cultural and historical perspectives of science, in particular chemical industry. Concluding Remarks The development of Color Science has included reflection about what characteristics make a science course academically rigorous, intellectually engaging, and produce the most impact on nonscience majors, students about whom educators have concerns about science literacy. Exploring these components by bringing together course evaluations, informal assessment data and elements within the liberal arts mission enables connection between student perspective and overarching standards, in this case bridging the nonmajor science student and appropriate goals within the liberal arts mission.
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Acknowledgments The author thanks Amy Eshleman, Department of Psychology, Wagner College, who performed t tests and a correlation analysis on course evaluations, and the Megerle Foundation of Wagner College for support of course development. Literature Cited 1. Rogers, G. Course Syllabus for SC332: Color and Light, Department of Science and Math, Fashion Institute of Technology, New York, 2000. 2. Department of Science and Math, Fashion Institute of Technology. Course Descriptions. http://www.fitnyc.edu/aspx/ Content.aspx?menu=Present:SchoolsAndPrograms:SchoolOfLiberalArts: ScienceAndMath:CourseDescriptions (accessed May 2006). 3. Klotz, I. M. J. Chem. Educ. 1992, 69, 225–228. 4. Tro, N. J. J. Chem. Educ. 2004, 81, 54–57. 5. Druger, M. J. Coll. Sci. Teach. 2001, 31, 134–135. 6. Hazen, R. M.; Trefil, J. S. J. Chem. Educ. 1991, 68, 392– 394. 7. Caprio, M. W. J. Coll. Sci. Teach. 1999, 29, 134–137. 8. National Science Foundation, Division of Science Resources Statistics. Science and Engineering Indicators–2002: Conclusion. http://www.nsf.gov/statistics/seind04/c7/c7c.htm (accessed May 2006). 9. Singh, B. R. J. Chem. Educ. 1999, 76, 1219–1220. 10. Singh, B. R. J. Chem. Educ. 1995, 72, 432–434. 11. Garfield, S. Mauve: How One Man Invented A Color That Changed The World; Norton: New York, 2000. 12. Seymour, E. Student Assessment of Learning Gains. http:// www.wcer.wisc.edu/salgains/instructor/ (accessed May 2006). 13. Wagner College Bulletin 2002–2004; Wagner College: Staten Island, 2002. 14. Cronin Jones, L. L. J. Coll. Sci. Teach. 2003, 32, 453–457. 15. Lord, T. R. J. Coll. Sci. Teach. 1999, 29, 59–62. 16. Ward, R. J.; Bodner, G. M. J. Chem. Educ. 1993, 70, 198– 199. 17. Nassau, K. The Physics and Chemistry of Color: The Fifteen Causes of Color, 2nd ed.; Wiley: New York, 2001. 18. Rossotti, H. Colour: Why the World Isn’t Grey; Princeton University Press: Princeton, NJ, 1985. 19. Overheim, R. D.; Wagner, D. L. Light and Color; Wiley: New York, 1982. 20. Ball, P. Bright Earth: Art and the Invention of Color; Farrar, Straus and Giroux: New York, 2001; pp 139, 150–153, 155, 199–202, 320–325, 335. 21. Zollinger, H. Color: A Multidisciplinary Approach; Wiley: Weinheim, 1999; pp 49–56. 22. Mayer, R. The Artists Handbook of Materials and Techniques, 5th ed.; Viking: New York, 1991. 23. Berns, R. S. Principles of Color Technology, 3rd ed.; Wiley: New York, 2000; pp 151–173.
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