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William F. Coleman Wellesley College Wellesley, MA 02481
From Our Peer-Reviewed Collection
Randall J. Wildman University of Wisconsin–Madison Madison, WI 53715
We continue to add to our peer-reviewed collection of WWW-delivered instructional materials. Our latest addition is Equilibrium. Using Shockwave, Sandberg and Bellamy have developed a visual, interactive approach to teaching and learning about chemical equilibrium using the nitrogen/hydrogen/ ammonia system. It is the first item in our collection to include a Spanish translation. Equilibrium Matthew Sandberg and Michael K. Bellamy,* Chemistry Department, Northwest Missouri State University, Maryville, MO 64468; *
[email protected] Students are often taught standard methods for solving equilibrium problems—methods that they then apply to solving similar problems on homework assignments, quizzes, or exams. When asked questions designed to ascertain whether they understand what actually occurs in an equilibrium system, the same students often answer incorrectly. What seem to us small modifications in a problem often cause students to have great difficulty solving the problem. Thus it is generally accepted (1) that students who score well on examinations do not necessarily understand the fundamental concepts of chemical equilibrium. The general chemistry textbook is not the problem with teaching and learning chemical equilibrium. Textbooks usually contain good written descriptions of the topic with instructive accompanying figures; the equilibrium table approach in most textbooks is also useful. However, textbooks are often ineffective at helping students visualize a concept well enough so that they can make predictions and apply concepts. The goal of the applet described here is to help students visualize some aspects of chemical equilibrium. We began by compiling a list of different aspects of chemical equilibrium that we thought could be taught effectively using a visual approach. Based on this information, we programmed this applet that allows students to add colored balls to a reaction chamber. Each ball represents 0.5 moles of N2, H2, or NH3. Click-
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Screen from Equilibrium showing an initial system and an equilibrated system.
ing the “Equilibrate” button displays the equilibrium concentrations of each gas in a chamber that is next to the initial chamber. Thus, students can see how many of each colored ball are present initially and after equilibrium concentrations have been reached. Students can vary the starting concentrations of any of the gases. They can also change the value of the equilibrium constant by changing the temperature of the system. The initial and equilibrium concentrations of each gas are given in an equilibrium table. The value of “X” that would be obtained by solving the equilibrium constant expression is also listed. The applet can be used by the instructor in the classroom as the topics are introduced and by students for individual study. Sample exercises for students are included. The text is available in English and Spanish. Literature Cited 1. Nurrenbern, S. C.; Pickering, M. J. Chem. Educ. 1987, 64, 508–510.
Journal of Chemical Education • Vol. 80 No. 4 April 2003 • JChemEd.chem.wisc.edu
