edited by GEORGEB. KAUFFMAN CBlifornia State University. Fresna Fresno. CA 93740
The BedBugS Game-A
Molecular Motion Simulator
Lynn Hogue Greenhills High School, Cincinnati, OH 45218 John P. Williams Miami University-Hamilton, Hamilton. OH 4501 1
A student's understanding of a scientific concept often can be enhanced with a visual aid, especially one of a commonplace nature. This paper describes the adaptation of a eame to r e ~ r e s e n tvarious a s ~ e c t sof molecular motion'. Although molecular-motion dekonstrators are commerciallv available2. this game is a novel and less expensive alternag i ~includes 48 plasticbedbugs in four tive. he ~ e d ~ ugame colors and a game surface that consists of a plastic and cardboard "bed". The pieces move in a random motion as a result of vibrations caused hy a battery-powered motor. The amount of vibration is damped either b y lifting the game surface with one's fingers, or, as shown in Figure 1,by usinga 10-i7 rheostat wired in series to one of the "C" batteries. Figure 2 shows the dimensions of a block of wood that represents a gas-porous membrane that must be made for several of the demonstrations.
I This simulator was developed as a final project for "Teaching Science with Toys", a workshop supported in part by the Ohio EESA Program under grant 5.20 and by Miami University. For example. Shakhashiri. 8. 2. Chemical Demonstrations; Wisconsin University: Madison. Wi. 1985; Voi. 2. pp 96-100. Two Sources: Sargent-Welch #1710M and Central Scientific Co., #31365. Made by the Milton Bradley Company, it is readily available in toy stores.
Molecular Motlon Simulation The crystalline pattern of a solid is represented by placing the bedbugs in an ordered pattern on the game surface. With significant vibration damping, the "particles" just quiver and maintain their orderedpattern. Decreasing the damping parallels an increase in temperature and kinetic energy; the
Figure 1. The BedBugs game with the "porous membrane" (wwd block) and ''dbretlon damper" irhewtet) modifications (photo by M. Henfling).
Volume 67 Number 7 July 1990
585
Dlnuslon and Effuslon Diffusion is simulated by centering the wooden "porous memhrane" between the plastic sideboards of the game surface,as shown in Figure 1. (It should fit snugly hut above the rardhoard surface so that vibration is not damoed.) Bues of one color are placed on one side of the barrie; and hugs of another color on the other. When the motor is turned on. the hugs move in a rapid random motion, and so some of each color pass through the "memhrane" to the opposite side. The effects of molecular collisions are exhibited by hugs humvine into one another in the "membrane" ovenine. Effusion issimulated by placing the hugs on just one side of the "memhrane".
Figure 2. The wwden block made to represent lhe gapporous membrane: only me width need be precise in order lo ensure a snug fit.
"particles" move more rapidly, exhibiting the short-range order of a liouid. With little or no damnine. . -. the extensive "particle" motion demonstrates the random motion that occurs in the gas phase. This simulation avoids the negative conceptual impediment of those simulations in which greater motion is accompanied by a decrease in the number of ohsenred particles.
Graham's Law Graham's law indicates that molecules of lower mass have a greater average velocity than molecules of higher mass a t a eiven temoerature. With a set of hieher mass molecules ipairsof bigs glued together) on one s i i e of the "membrane" and lower mass (single hugs) on the other, the inverse relationship between mass and diffusion rate is clearly evident as more of the lower mass bum diffuse throueh the membrane. If the single hugs represent helium mole&les and the double hugs represent diatomic oxygen or nitrogen molecules, the demonstration is analogous to a helium-filled balloon. Even though there is movement through the harrier in both directions, the lower mass helium molecules exhibit greater movement. Thus the balloon loses volume and hecomes less huovant. Inshort, witha few minor adjustments, the RedBugsgame has proven to he a versatile teaching tool. Ry being visually presented various characteristics of molecular hehavior in this innovative way, students can gain a more complete understanding of these fundamental concepts of molecular mo~~~~~~~
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1991Award for Excellence in Polymer Education by a High School Chemistry Teacher Allactive highschool teacherr whoinelude polymer chemistry i n rhrir curricul~mandencuurageotherstodothe~ome are invited to apply for the 1991 Award in Excellence m I'olymrr Education by a High School Chemistry Teacher. The auards, s~onsorrdby the .lornt Polymer Edt~catlunCommlrt~e11JolvEd1oi thc ACS I'olvmer Chemlsrrs Dlvrsmn and ~o~vmeriE ~aterials;Science and ~neineerineDivision. honor two-national reci~ientsand three honorable mention recibients. Thr awards recc8gnne the ;;um.stnnding efrurts of hrgh school chrmistr), rrachrrs who educate youths ro he informed ririrena and to consider cereerx in ~hemistrv.Awards are h a s 4 on the applicants' innovative ure of classroom laborarory acrit,itiest o promote understanding of pdymer chemistry and its role in rhe products srudenti u6e daily and on applicants' outreach activities to encourage other teachers to explore polymer chemistry with their students. Deadline for the 1991 awards is January 15,1991. Applications can be obtained by writing to A. M. Sarquis, PolyEd High School Teacher Polymer Awards, Miamai University Middletown, Department of Chemistry,4200 East University Blvd., Middletown, OH 450042.
586
Journal of Chemical Education
