edited by
J. DUDLEY HERRON Pvrdue University West Lofoyene, lndiono 47907
Molecule Madness and the Balancing Game: Examples of Classroom Games Helen Schmitt Lane Technical H.S., Chicago, Illinois 60618 Molecule Madness Models have always played an important part in teaching honding abilities of atoms and shapes of the resulting molecules. An ideal situation would be one in which every student had his own model building kit. Because this is prohibitively expensive for most high schools, models are usually shown a t the front of the classroom by the teacher during a lecture. An attempt to involve students more led to the development of the model building activity called "Molecule Madness." The equipment consists of one set of . . a t m ~ i cmodt,ls wirh cmncrtlng pieces ior honds. T h e \ can Ilr rommercial car homemade. T h e models used in the a c t i v ity as described below are expanded polystyrene halls of various sizes, color-coded to indicate electronegativities, with black heads attached as valence electrons, holes in the halls for making connections, and toothpicks and pipecleaners a s the connectinn ~ i e c e s . Prior to the start of the &ivity the models are placed a t the front of the room. Students are instructed to choose one atom apiece, with which they will make honds. Next each identifies his own atom, based on its relative size and the number of valence electrons attached. The class is provided with a supply of toothpicks and pipecleaners. Students can bond their atoms to those belonging to other students to make molecules. The object is for the student to participate in as many different molecules as possible in the time allotted. Since this activity preceeds any actual discussion of honding, it must he established a t the outset that every honding position on every atom must he involved in honding. Completed molecules are shown to the teacher for approval and credit on a master score sheet, then dismantled so that each student is free to participate in another structure. Students should keep a record of the structures and learn their names from the text or the teacher. Through this activity some interesting parallels to actual behavior in bonding emerne. I t is more roba able that small molecules will formthan l&ge ones. he student who originally picks an inert gas atom hecause it appears so elaborate with its eight valence electrons soon finds himself out of luck. On the other hand, the student who is willing to settle for the far less glamorous hydrogen model is needed everywhere. T h e reason hehind the name "Molecule Madness" becomes apparent to anyone who enters the room when honding is in progress. In order to insure the huilding of a large variety of molecules it is suggested that only a few types of atoms he available, and those in varying quantities; hydrogen being most abundant, followed by oxygen; carbon, nitrogen, chlorine, sulfur, and perhaps an alkali and an alkaline earth metal. 172 / Journal of Chemical Education
This activity does not teach many more complex aspects of honding, such as resonance structures and coordinate covalent bonds. nor is that its intent. If the student has felt a sense of accomplishment in discovering, on his own, these simple structures, he will he more receptive to a detailed discussion of honding and if he never learns anything more than this about honding, he will a t least remember this activity and in so doing, will understand something about molecular structure. Balancing Game T h e second activity is the "Balancing Game" and is used to teach the halancine of simole eauations. T h e class is divided into two teams.-~hee&ation balancing is conducted on a blackboard a t the front of the room that has been divided into two halves, one for each team. An unbalanced equation is written on each side. The two equations should not he identical but should be of the same order of difficulty. Students take turns coming to the hoard to help halance the equation. Each student is permitted to write in one coefficient or erase one mistake made earlier as his move. He may not make both moves hut must make a t least one. If the student whose turn it is believes the equation to he correctly balanced a t the start of his turn, he raises his hand. This action ends the play for his side. The round ends when someone on each side has raised his hand. The side which finishes first wins the round only if it has balanced the equation correctly. If neither side balances the equation correctly, nobody wins the round. Communication between team members during play disqualifies that team. Equations cannot be balanced by the students a t their seats, either. The following example typifies a round during the first day balancing is taught: Teacher writes: Hp + N2 NHs Student (1) incorrectly adds subscript: HZ+ N2 N2Hs Student (2) erases mistake: Hz + Nz NH3 Student (3) adds coefficient:Hz + NZ 2NH3 Student (4) adds coefficient: 3H1+ Np 2NH3 Student (5) fails to recognize balanced equation, adds coefficient: 3H2 + 2N2 2NH3 Student (6) erases mistake: 3H2 + N p 2NH3 Student (7) rases hand, ends play Students gain skill in balancing simple equations quickly through this activity because they learn from one another's mistakes and are under pressure from other students not to repeat the same errors from one round to the next. For example, students are taught that subscripts of a correct formula cannot he changed in the process of halancing the equation hut too often this advice goes unheeded. Peer pressure from fellow students during the game drives the point home much faster than the teacher's explanation and pleading could ever do. The balancing of more complex oxidation-reduction equations can also he taught through this activity. It is only necessary to include a few additional moves such as writing in oxidation numbers of appropriate half reactions. No specific moves are outlined here. The individual teacher
-
-- --
should devise his own, based on his method of teaching the balancing of oxidation-reduction equations. One final note in support of activities which involve the
students; the class enjoys what it is doing and, therefore, the atmosphere within the classroom becomes positive and stimulating to everyone-including the teacher.
Volume 53,Number 3. March 1976 / 173
