Wichita State University Wichita. KS 57208
ment is given, students are encouraged t o work individually within a small group setting where questions can be asked and answered quickly. When walking around the room, you bear the key words over and over-"Mole Bridge", "Given", Askedfor", and "change yourself into a mole".
A Stoichiometrlc Journey Brlan Molle Platteville High School Planevllle, WI 53818
Some of the common problems students have with stoichiometric calculations &e (1) where to start the problem, (2) when to use the mole ratio, (3) why to use the mole ratio. (4) which mole ratio to use, and (5)how to recognize when the problem iscompleted. The following littlestory will help the student overcome these problems. The students like it. and it has proven effective in teaching stoichiometrir ralculations hv thedimensional-analvsis method tostudents with a fairly wide range of intellectuh abilities. The story allows the students to solve stoichiometric oroblems while still struggling with the conceptual side of the problem. The Story
Once upon a time, you lived in a town by the name of Given. You had some friends who lived in the nearby townof Askedfor. One day you decided to visit your friends in Askedfor, but the only way to get from Given to Askedfor is to cross "Old Mole Bridge". The reason they call i t "Old Mole Bridge" is that only moles are allowed to cross. So the only way to get to Askedfor is to change yourself into a mole and cross the bridee. Now vou don't want to be a mole anv loneer than you have to, so after crossing the bridge you change vourself back, and you've made i t to Askedfor. Three or four examples are presented to the class before an assignment is given. In the solving of each example the story is told and related to the problem. When the assign-
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The Story a s a Conceptual Aid The idea that one can move from one part of a chemical reaction to another and that these parts are distinct, measurable, and yet related is a very difficult concept to relay to beginning chemistry students. This type of learning aid has proved helpful, since the story continually emphasizes the mole relationship in the journey. The mole becomes the dominant character in the story, and this emphasis carries over into the calculation process. Students become aware that the mole is the "mode of transportation" through which these t w e s of nroblems are solved. ~ h & t e a c b & ga class that contains students with a wide ranw of intellectual abilities. one encounters students who easiiy conceptualize even difficult topics such as stoichiometry as well as those who must struggle to conceptualize even a t a basic level. This story approach has allowed students to succeed in solving stoichiometry problems while still working on their conceptual understanding of the topic. Although thisappearsto be rote memorization, which it may be a t the beginning for some students, i t develops into a higher level of conceptual understanding for many students. In fact, since this story has been introduced, the average student score on the stoichiometric lesson showed a 0.96 letter grade improvement over students from the previous two years who did not use this method.
Volume 66 Number 7 July 1989
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