~~
view fo m my ckmoom
~~
~,
CLAIRE H. SMITH San Francisco University High s
c
~
~
1
~
Using Chemistry's Crystal Ball Bill Allen Stevens Point A r e a Senior High, 1201 N. Point Drive, Stevens Point, WI 54481
The period is rapidly drawing to a close. Several srudents are intently reading the Hnndhook of Chemistry and Physics. Cruups oistudents arr carefull\.studying periodic tables that are posted around the room.~livelydiscussions about density, boiling point, freezing point, ionization energy, and other trends are taking place throughout the room. The bell sounds and astudent exclaims, "Is the period over already?" The above may sound like some kind of fantasy, but I have witnessed it many times over the last few years during our unit on ~eriodicitv.The reason for this "ideal" educational environment is adexercise we have developed called "Using Chemistrv's Crvstal Ball". ' ' ~ s i n & h e ~ i s t r ~ Crystal 's Ball" is an exercise requiring students to identify nine elements, eachsuggested by a set of four to six clues describing physical and chemical properties of an element. The students must not only identify each element hut also must heable todescribe how evrry clur was useful and the order o i usage o f t he clues from must general to most specific. The first two of the nine problems are multiple choice so as to narrow the selections and help in the adjustment to this new kind of assignment. Then, a rather easy multiple-choice type of problem is worked as a class examole. w 2 t i n g a set of clues can be as much fun for the teacher as solvine the ~ r o b l e mcan be for the student. Following are three examl;les of problems that we have used: (1) (a) higher ionization energy than Rb (b) forms X 2 0 (4 mp close to bp of HzO
(d) size of atom is larger than CI (a) K (b) Cs (4 Mg (dl Na (4 S (2) (a) a colorless gas (b) more dense than air ( e ) mp about -200 'C (dl will not react with K (e) occurs as a liquid over a 4 to 5 OC range (3) (a) might he a liquid or a solid in the laboratory (b) silver color (c) formula for chloride of this element is XCI id) low density (el low bp (0 atoms of this element will he oxidized by AP+ ions In the eves of our students. the "correct" answers would be (1)Na Ar (3) Cs. The students are given two 50-minute class periods to use classroom resources-to work on the assignment. These resources include periodic tables with much information that are posted around the room, several copies of CRC H a n d book of Chemistry and Physics, and high school and college freshmen level chemistry texts. T o h a p motivate the s&dents to do a good job, they are told that in three days they may have to present and defend their selections before the class. We do our best to make this nonthreatening and tell
6)
them that there may be no right or wrong answer but that logical reasoning is considered to be the goal. We make the assignment analogous to a detective working with clues and then as a lawyer presenting the case to jurors (fellow students). On the third day, Chemistry Court is in session. We announce that everyone has full credit for the assignment and that they could only lose it by being called upon for a problem and having nothing to say, or doing apoor job (not using most of the clues), or by being an impolite juror. Names are drawn from a hat t o select who will make a presentation. After each presentation the judge (teacher) asks for a vote of agreement or disagreement. Members of the jury (class) may then comment or present alternate cases. We avoid talking in terms of an element being right or wrong, but which answer can best be justified by the clues. Any student absent for any reason must submit a written report of all nine problems. Sometimes i t seems the only cure for the "public speaking flu" is a prescription of formal writing. The major goal of this exercise is to learn trends of properties of elements and to understand that these trends can be related to the arrangement of the elements in the periodic table. This exercise also exposes students to a variety of information. Many of the clues are purposely vague so that students develop their reasoning and discover that in a problem situation the information one has t o work with is often neither black nor white. T o emphasize this, several of the problems have more than one possible element that can be justified. Finally, this exercise gives the students an opportunity to practice verbal communication in science, which is too often neglected. Usually the students do a very good job in presenting their cases. Equally impressive is the attea-
the University of Massachusetts, having been awarded a BS in Chemistry in 1946 and an MAT in 1969. She has taughl chemishy at the San Francisco University High School since 1976. Along wilh her regular teaching assignments. she has directed the NSF-funded Bay Area High Schaal Chemistry T e e cher's Project. An active member of the American Chemical Society, Claire has served as the councilor for the California Section and as a member of DIVCHED's High School Chemistry Commitlee. She is a:so very active in the California Association of Chemistry Teachers and the National Science Teachers Association.
Volume 64
Number 3
March 1967
I
227
:
l
~
tiveness and politeness of the jurors. When there is disagreement, a logical discussion follows, which indicates that we have achieied our goals, Team Teachlng Chemistry at S A S H
Stevens Point Area Senior High School (SPASH) is located in Stevens Point, Wisconsin. SPASH is one of the largest high schools in the state, hut faculty and students enjoy a snecial closeness.. oerhans due t o our student advisorv, nro. . gmm, which promutes the "atmosphrre" of a smaller school. In May 1985, SI'ASH was one of the 12 schools in Wisconsin to receive national recognition 1)). the I!. S. Department 01 E d m a t i m as an outstanding secondary school. There were 212 such schools nationwide. Over SO"& of our appn)ximatelv 1740 students take one of two beginning che&try couses during one of their three years a t SPASH. Both courses use Harper and Row's series of modules Interdisciplinary Approaches to Chemistry (IAC), which is very laboratory oriented. About 30% of our first-vear students take the 1A-2A course which is desiened for &dents who plan a career in a science-related field.- he IAC materials are richlv sunnlemented in this course. Our 12 course is designed f i r stidents who wish to know more about chemistrv and how i t relates to the world around them hur who u,ill probahly not takr more science courses. We are hoping that the promising new CHEMCOM curriculum will
228
Journal of Chemical Education
soon he available for implementation in this course. We also offer a third-semester advanced chemistry course that is designed to help further prepare science-oiiented students for freshman college chemistry. Finally, a few words on the use of the word "we" in this article. Chemistry a t SPASH is team taught in one room by two teachers per period. There are approximately 48 students in a class. This requires careful planning, close partnershio. .. and the ahilitv to eet to know twice as manv students as a typical classroom teacher. T o complicate matters further. our enrollment in chemistrv has increased so much during the last few years that we now have three chemistry teachers who team in every combination during the day. There are disadvantages and advantages to such a teamteaching arrangement, but we feel that the advantages outweigh any negative aspects for both the instructors and students. I t seemsvery difficult after 12years of team teacbing to use the word "I".Ideas are shared and improved upon by constructive criticism. Alternate methods of presentation are explored and praise is given when a job is well done. These are luxuries and fringe benefits that few in our profession share.
- -
Acknowledgment
I would like to thank N. Allen, J. Sporakowski, and R. Sus for their comments on the manuscript.
