Sheldon H. Cohen
Washburn University of Topeka Topeka. KS 66621
Exploring Chemistry for Junior High Students
A report of a course, "Exploring Chemistry for Parents and Children," was recently published in this Journal.' The enthusiasm for science shown hy the participants was one of the most positive outcomes of this program. 1n response to strong pressures brought by former students, a second more advanced offering was designed by the university faculty for children of junior high age with strong interest in science. This naoer will reoort the details of this follow-uo course. "Exploring chemistry for Junior High students.;' The prigram consisted of five weekly, two-hour evening sessions. As in the earlier offering, chemistry principles were learned from experimental observations instead of from formal lectures. The only materials covered in the classroom were brief prelaboratorv discussions. S ~ e c i ael m ~ h a s i was s placed on aood experimental techniqies, such-as the proper hanzling of chemicals, the use of safety equipment, and the correct manipulation of instruments. Whenever applicable, the students did quantitative determinations on unknown samples. This allowed the participants to grade their techniques, and to feel the pride of accomplishment when excellent results were obtained. On those experiments which were also done in a standard college freshman laboratory, the junior high students' results compared very favorably. First Session
Acids and Bases-The effects of acids and bases on a number of indicators were ohserved. Acidic, hasic, and huffered neutral solutions were tested on a pH-meter. Each student was given 100 ml of an oxalic acid unknown solution. With the use of sodium hydroxide, standardized earlier by the instructor, and traditional acid-base titration procedures he was required to determine the normality of a t least three separate 10.0 ml aliquots of the acid. The students were expected to obtain results within 1%of the approved value. Second Session
Chemical Reactions-The top loading analytical halance was demonstrated. The students then spent a short time studying various qualitative tests which could he used to determine the presence or absence of copper ions in solution. After each participant had reported his procedure to the instructor, he was given an unknown solution containing copper sulfate. The copper ion was displaced with zinc metal, and the excess zinc was removed with hydrochloric acid. After being washed with distilled water and dried. the comer was weiehed. A comparison was made with the approvedvalue so that the student could judge his technique.
Fourth Sesslon
Chemical Equilibrium-With the use of test tube reactions the effect of varying concentration was studied for the iron (111)-tbiocyanateand chromate-dichromate equilibria. Since the students were looking a t color changes, the side topic of spectrophotometry was introduced at this time. A number of colored solutions at various concentrations were studied with the use of a manual spectrotophotometer. The relationship hetween concentration and absorbance was determined. The effect of temperature on an equilibrium was demonstrated in the laboratory by the instructor using the cobalt chloride ~ystem.~
E C 0 N D A R factors which effect the speed of y
Fifth Session
Chemical Kinetics-The a reaction (nature of the reactants, state of subdivision, presences of a catalyst, concentration, and temperature) were examined. The first two factors were demonstrated by the instructor in the laboratory. Various metals (zinc, copper, and sodium) were placed in dilute hydrochloric acid to show the effect of the nature of the reactant. Powdered cornstarch blown into a flame and the burning of a large crystal of sugar were used to comnare the effect of article size. The students then studied the Lolume of ovyge'collected over water for a eiven leneth of time when ootassium chlorate was heated with "nd wittout manganese dioxide catalyst. The old chemical rnaair clock reaction. the formation ot colloidal arsenic sulfide. was used for the &udy of the effects of concentration and temperature on the rate of reaction.3 Concluding Remarks
After the comoletion of the five-week momam an extremelv favorable evaluation was obtained from a i t h e participants. In discussions at the end of this Dromam t . .. one maior . .~ o i nwas constantly stressed hy the students. Teachers ofscienre who deal with students below the hiah school Iewl often expect too little from them in both laboratory competence and interpretation of scientific observations. A great deal of the success of this program was credited by the participants to the fact that they were expected to obtain results limited only by the accuracy of the equipment used, and they were required to independently determine basic concepts of srienre from their ~
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Third Session
Thermochemistry and Chemical Reaction-This experiment was similar to that reported earlier except the students were required to make quantitative calculations on the reactions which previously had been studied only qualitatively.' In addition the heat of fusion of ice was experimentally determined.
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I ~ o h c nS. . H.. .I. (.HEM. EDL'C., 56,736 (19-91. 2Clte11,1'. S.. "Entertaininr! and Educational Drmonatrntron," Chem:cal Elements Puldishing Cu., Carnarillo. Cnlifornia. 1971, y.
36.
Chen, P. S., "Entertaining and Educational Demonstration," Chemical Elements Publishing Co., Carnarillo, California, 1974, p. 30.
Volume 57, Number 10, October 1980 / 723
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