edited bv

Highlights SUSAN H. HIXSON

National Sctence Foundation Arlington, VA 22230

CURTIS T. SEARS, JR. Georgia State University

Atlanta, GA 30303

- .

Projects supported by the NSF Division of ~ n d e r ~ r a d u a t e Cducation An Interactive Multimedia Software Program

for Exploring Electrochemical Cells

Thomas J. Greenbowe Iowa State Jn Yerslly of Sc~ence and Techno ogy Arnes, IA 50011

Many chemical processes are difficult to communicate ef- fectively because the concepts require individuals to visu- alize the movement ofmolecules, ions, or electrons. Herron and Greenbowe (1) have stressed the importance of in- structors helping students make connections between three levels of representation: macroscopic, microscopic, and symbolic. Static diagrams, graphs, chemical equa- tions, mathematical equations. and chemical symbols are part of the symbolic ievel of representation. ?:hemistry demonstrations and laboratory actirities idlow students to directly observe chemical reactions at the macroscopic level. Amissina component of instruction is a way to con- vey the m i c r ~ ~ ~ i c level of representation of a ihemical process. Explaining dynamic processes of equilibrium re- actions and-oxidation&ductibn reactions becomes easier when students can observe a computer animation or simu- lation of these processes.

McPhillen and Greenbowe (2), Lynch and Greenbowe (31, and Greenbowe and Parker (4) have developed computer animated sequences and interactive multimedia instruc- tional programs for use in introductory chemistry. The "Electrochemical Cells Workbench" is one component of a software package that allows students and faculty to ex- plore building and testing electrochemical cells. The "workbench" is a microworld environment simulating a chemistry laboratory in which a student can perform ex- periments. The "workbench" section of the program pro- vides students and instructors the opportunity to manipu-

Figure 1. A computer screen image of the electrochemistry work- bench showing three aqueous solutions and two beakers.

Figure 2. A computer screen image of the electrochemistry work- bench showing a voltmeter, metal electrodes, wires, and saltbridge.

late experimental apparatus, chemicals, and instruments in order to design and build an experiment. Students use a mouse to "point-and-drag" objects on the screen that repre- sent beakers, various metal electrodes, salt bridge, wires, and a voltmeter to seeup and test an electrochemical cell. For example, when viewing the screen the student selects three solutions to work with from a menu of 12 solutions. The solutions appear as labeled reagent hottles on a shelf. Beakers are moved under the spigots of each bottle. The spigot from a bottle is opened to allow the solution to fill one of the beakers. Figure 1 shows a computer screen of the chemistry workbench with three 1.0 M aqueous solu- tions to choose from. In this example, the student is choos- ing to work with aqueous 1.0 M coppedII) nitrate in one beaker and aqueous 1.0 M zinc nitrate in another beaker.

The menu of aqueous solutions also includes the option of working with 0.10 M, 0.010 M, and 0.0010 M aqueous solutions. enabline students to exolore concentration cells and calklations i&olviug the st equation. Next, the student selects metal electrodes to lace in the solutions. A menu presents various metal electiodes to choose from. If a student wants to explore building an electrochemical cell by placing a zinc metal electrode in copper(I1) nitrate solu- tion and by placing a copper electrode in zinc nitrate solu- tion, the program will do so. This is an important compo- nent of interactive multimedia: the user is presented with decisions to make just as if he or she were in a laboratory working with electrochemical cells. The program prompts students with hints if they are having trouble setting-up a cell, and there is a help menu also. Figure 2 shows the com- ponents of an electrochemical cell being assembled. One beaker contains 1.0 M coppedII) nitrate and a copper elec- trode; a second beaker contains zinc nitrate and a zinc elec- trode. Avoltmeter, wires, and a salt bridge are available.

The student moves the wires to connect the electrodes to the voltmeter. Again, the student must make a decision: which electrodes should be connected to which terminals.

Volume 71 Number 7 July 1994 555

Figure 3. Acomputer screen image of a copperlzinccell with a digital color overlay (right).

A salt-bridge must be inserted connecting the two beakers in order to complete the circuit. If students connect the wires one way and obtain a negative voltaze on the voltme- ter, they can readily change the connemions of the wires to obtain a positive voltage. When the elec~rochemical cell is assembled, a color digital photograph ol'a similar electro- chemical cell connected to a voltmeter is displayed along- side the simulated cell as shown in Firmre 3.

After assembling an electrochemical cell, the student has the option of viewing animation sequences on two scales. The first scale shows an animation of the entire electrochemical cell. The student observes simultaneous oxidation-reduction reactions occurring at each electrode, migration of ions in the solutions, migration of ions within the salt-bridge and at the ends of the salt-bridge, and di- rection of movement of electrons in the wire. This view re- inforces the dynamic nature of electrochemistry and pro- vides students with a representation at the microscopic level. Figure 4 shows a computer screen of one frame of an animation for a copper-zinc electrochemical cell. A mouse is used to "click-on" control panel buttons that pause, move ahead one frame a t a time, move backwards one frame at a time, repeat, or exit the animation.

The second scale of animation allows users to click-on areas of the cell to observe a "zoom view" at the atom or ion level as shown in Figure 5. Zooming in on the copper elec- trode shows copper(I1) ions in solution and copper atoms comprising the electrode. As electrons are shunted down

Figure 4. A computer screen image of a copperlzinc electrochemi- cal cell.

Figure 5. Acomputer screen image of acopperlzincelectrochemical cell with zoom, click-touch areas.

the electrode, copperiII) ions move toward the electrode where they each acquire two electrons. When the electrons are awuired. the size of the co~~er ( I1 ) ion increases as it becomes a copper atom and atta%est;the electrode. Com- uuter animation helus make the connection between the chemical symbols, ci21(aq) + 2 e -> Cub), and the mi- croscopic level of representation of this process. Figure 6 illustrates the reduction process occurring at the cathode. -

A small image of the copper-zinc cell appears in the up- per right-hand corner with a box around the copper elec- trode to help students recognize that what they are view- ing is the enlarged area around the copper electrode. I t also serves to reinforce to students that other processes are happening simultaneously in the cell.

While comuuter-animated sequences are fine for simu- lating dynamic motion of molehes (microscopic repre- sentation), students need to be able to connect these mod- els with actual chemical processes. Used by instructors in their lecture presentations, the animations are most effec- tive when coupled with live demonstrations of electro- chemical cells. In the laboratory, students construct sev- eral electrochemical cells using metals, solutions, a salt bridge, wires, and a voltmeter. Before they measure the voltage, the students draw a diagram predicting the loca- tion of the oxidation and reduction processes, the move- ment of electrons in the wire, migration of ions within and at the ends of the salt bridge, and the identity of the anode and the cathode. They check their predictions with the

Figure 6. Azoomed-in image of a representation of a copper elec- trode functioning as a cathode.

556 Journal of Chemical Education

computer animation. Of particular interest is the discov- ery by students that a negative voltage does not indicate that the electrons and oxidation-reduction process is re- versed.

The results of preliminary studies indicate that the pro- gram helps students achieve a better conceptual under- standing of the processes occurring in electrochemical cells. These studies also indicate that student learning styles play a role in whether or not students benefit from viewing and working with the animations, simulations, and instructional modules. The interactive multimedia program becomes a problem solving tool, a wnceptualizer, and a tutorial for the student.

Acknowledgement The National Science Foundation Division of Under-

graduate Education has provided support for this project through Grant No. DUE 9253985.

Literature Cited 1. Hermn, J. D.; Greenbowe, T. J. J Cham Edue 1986,63. 528. 2. Lynch, M ; Greenbowe,T J. "An InteractiveKineties Program'.Apaper presented at

the 12th Biennial Conference on Chemical Education, University ofCalifornia - Davis. Davis. CA, Augvrt 6.1992.

3. McPh3len. M. A ; Greenbowe, T. J. "An Int t tadi~e E l ~ t t h h m i i i l Cell Programgra.A paper presented at the 12th Biennial Conference on Chemical Education, Univer- sity of California-Davis, Davis, CA, Avgvrt 6, 1992.

4. Greenbowe, T J . ; Parlte~ M. M. l l s ing Interactive Multimedia To Help Students understand f i n p l e a and concepts of ~ ~ ~ ~ t ~ = h ~ ~ i ~ ~ ~ C ~ I Y S . A~~~~ presolted nf the American Chemical Society meetin& San Diego, March, 1994.

Science Education Is Focus of New RCS Prosram - - -- -

The recently reestablished State and Lacal Government Affairs program (SLGA) within the American Chemical Society's Department of Gavemment Relations and Science Policy will aid ACS members in pmduetively interacting with their state and local deeisianmakers. The initial focus of the Proeram will be science education a t the elementaw and secondary level.

Wide acceptance of the need to reform education in the United States exists. Efforts by the Nation's governors and recent congressional passage of legislation supporting the development of national standards testify to this fact. While the American Chemical Saiety and many other groups contribute to Congress's development of federal education policy, much of the reform activity is centered a t the state and local levels. The SLGA program will help fill this niche and build on the work underway in many ACS Local Sections across the country. Through distribution of information on related bills pending in state legislatures and on local reform measures, the Pmgram will enable ACS members to become a force in shaping education reform to the benefit of the sciences. A Public Affairs Kit, newsletter, and other materials will allow even those previously unversed in dealing with public officials to get involved.

State legislatures offer a unique opportunity to affect public policy on a wide range of issues affecting chemistry- from edueation to environmental protection. Legislators a t the state level are much more accessible than their Wash- ington counterparts. Many also hold other full-time jobs, making the availability of reliable and informed advice fmm constituents vital. With approximately 150,000 members in 186 Local Sections across the country, the American Chemical Society is well situated to provide such information. The mix of its members'industrial, government, and academic backgrounds affords the Society credibility lacked by groups representing narmwer interests.

In the education area, the Society Committee on Education (SOCED) is providing policy direction to SLGA. SOCED bas selected several areas for emphasis: (1) measures dealing with teacher training and qualifications, (2) account- ability for federal funds, and (3) programs to attract and retain populations underrepresented in the sciences. Afive- member Advisory Board provides strategic direction. The Board includes chemical professionals from industry, academe (precollege, two-year, and four-year institutions), and government (a state legislator).

To maximize its impact, SLGA has selected 15 target states in which ACS member networks will be established: California, Colorado, Delaware, Florida, Illinois, Massachusetts, Michigan, New Jersey, New York, North Carolina, Ohio, Pennsylvania, Texas, Washington, and Wisconsin. Members may request further assistance for other states or an additional issues.

While intended far American Chemical Society members, the SLGAnewsletter also will be useful to others following science education reform developments. Ta receive the free newsletter and other information about the SLGApragram, contact Bill Gray of the SLGAstaff. He i s a t the American Chemical Society, 1155 Sixteenth Street, NW, Washingtan, D.C. 20036,202/872-4391 (phone), 2021872-6206 (fax), or wtg93Bacs.org (Internet). ACS members requesting informa- tion are asked to identify their Lacal Section affiliation.

David R. Schleicher Depattment of Government Relations and Science Policy

American Chemical Society Washington, DC

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