Mary Ann Ryan Donald Robinson and JW Carmichael, Jr.' Xavier University of Louisiana New Orleans. LA 70125
A Piagetian-Based General Chemistry Laboratory Program for Science Majors
In recent vears. considerable attention has been eiven to Piaget's theory of intellectual development and its Lplications for science teaching. Of oarticular interest is the possibility that the theory Govides a basis for formulating instructional strategies which would encourage the development of problem-solving ability (Piaget's formal operational level) and consequently make the sciences more accessible to the educationally-disadvantaged. An excellent resource paper which reviews the literature concerning these, and related, topics has appeared in this Journal recently ( I ) . As one part of an effort to explore new methods of increasine oerformance in andlor decreasine attrition from entrv level s&ce courses, in 1976 the science departments at Xavier (a small, historically-black institution in New Orleans) initiated a cooperative program to develop and field-test Piaeetian-based materials. That effort led to the development or twenty-five laboratory exercises (five each from ~iology, Chemistw. Cornouter Science. Mathematics, and Phvsics), each organized & a "learningcycle" (2). ~ubsequentfieldtesting of these exercises for three years in a pre-freshman summer pwgmm for science majors(l'roject S O ~ ~ - S t r e s s On Analytical Reasoning) has indicated that their use produces statistirallv sirnifirant imorovement in SOAR oarticipants' ability to complete correctly activities beli&ed to measure reasoning ability (3-5).It is hoped, but not yet possible to prove, that this improvement is accompanied by a corresponding increase in ability to perform in entry-level science courses. Recoenizine that a six-week summer . oroeram, no matter how intensive, could not remedy all deficiencies (even if all entering science majors could afford to attend), in 19% the chemiitrydepartment at Xwier also began formulating lahoratory experiments similar to those in SOAR for use in its general ch&istry laboratory sequence for scieqce majors. The first stage of this effort, spurred on by the apparent success of SOAR, has now been completed. A full, two-semester sequence of experiments in the learning cycle format has been developed and has been in use in the general chemistry laboratory program a t the University since the fall of 1978. This oaoer for the . . discusses various asoects of the new oroeram . purpose of sharing ideas concerning methods of applying Piaeet's concepts within the traditional instructional framework and stimula'ting discussion of the problems which arise when attempting to do so in a course for science majors. ~~~~
~~
-
An Overvlew of the General Chemistry Laboratory Program at XU The eeneral chemistrv lahoratorv nroeram a t Xavier consists of two semesters 'bf weekly, 3-h;laboratory periods conducted bv full-time facultv. Each laboratorv class enrolls approximately 24 students each semester, almost all of whom are science majors who expect to complete two years of chemistry in addition to the general chemistry course. Students receive one-semester hour credit for completing each of the two laboratory courses while concurrently enrolled in corresponding, separate three-semester-hour lecture
".
"0111SR9 ..--. . . .
Until recently the general chemistry laboratory experiments a t Xavier were traditional, content-oriented exercises which 'Author to whom inquiries should be directed. 642 1
Journal of Chemical Education
stressed skills and verification of chemical principles with detailed explanation and instruction a t every step. This approach appeared to be very good for teaching laboratory skills and was effective, for many students, in teaching/reinforcing a variety of chemical principles and calculations of value. However, because traditional experiments primarily required verification of ideas which had already been spelled out in detail a t the outset of the experiment, they provided little opportunity for the educationally-disadvantaged student to gain experience in "doing science" or to develop the ability needed to analyze data (or solve problems) of a general nature. Therefore, because the success of SOAR indicates that experiments in the "learning cycle" format potentially enable educationally-disadvantaged students to overcome deficiencies, the chemistry department chose to initiate its current laboratorv full. two-semester seauence of . oroeram-a . "learning cycles." Generallv, laboratorv experiments in the learnine cvcle format p~aEemore emphasison learning by doing than iithe cnse for traditional verification experiments. Ench learning cycle consists of three phases: exploration, inuention, a n i application (discovery). The phases, and what occurs in each during a lahoratory period a t Xavier, are described briefly below. In the first of these nhases.. ex~loration. the student is al. lowed to interact with concrete materials to acquire information about a given chemical or ohvsical svstem with a minimum of guidance. The student;^ given only a brief introduction to needed laboratorv skills, a review of safetv precautions, and such general giidelines as are necessary tb estahlish sufficient limits to ensure that the experiment can he completed during a 3-hr laboratory period. NO theoretical introduction is given and the student is not given any prior information about what relationships to seek. Whenever practical, individual students (or groups of them) are allowed t o determine pertinent variables for the system. The instructor seldom attempts to eliminate extraneous factors (and often .ourooselv introduces them). . . and students are allowed . to make non-dangerous mistnkes without interference. The student would normally complete t h ~ activity s hy the midpoint in the laboratory period. If this is not enough time to collect the amount of data needed for the desired analysis, an indi\,idual's data would be pooled with that from .'another lat~oratnrvsection" (carefully selected tw the instructor) or with thatfrom classmates. In the second phase, invention, the student is asked to analyze the data gathered during exploration. As appropriate, analysis might include seeking relationships between variables, making generalizations from these relationships, constructing graphic presentations, and developing an empirical equation which describes the r e l a t i m ~ h i ~ ~ ~ m ~ t h e m a ~ c a l l ~ . As in the previous phase, the instructor dues not tell the student merely to verify a known answer but rather asks questions which guide the student to develop a logical analysis of the data. In so doine. ,.. the instructor does not discouraee ,. investigation of chemically unimportant relatinnihips(such as the rrlationshin hetween heirrht and volume of a cvlindrr in " an experiment designed to emphasize density) but instead encourages further investigation to see what other relationships might exist. Students are actively encouraged to work in pairs (or larger groups) in the invention phase. In addition, the phase is usually initiated by a short, instructor-led pre-
liminary discussion of the data which is intended to suggest possil)le considerations rather than to pro\.ide specific answers.'l'he a h v e descriptionshould not he read to imply thnt a student is expected to "invent" all of modern chemistry in derail. Instead. tht, laboratorv" r)rormm focuses un acuuisition . of concepts of a general nature as a basis for more detailed studv in the corresoondine lecture. g t h e final phasi, appli&tion, the student extends the basic concepts from invention in some manner. This stage - mieht include making predictions based on concepts developed, conducting student-designed experiments which test the prediction, or (occasionally) using self-designed experiments t o investigate an area closely related to one studied previously. The general chemistry laboratory handouts a t Xavier re-
-
Table 1. Synopses of Selected Learning Cycles Exploration invention:
Mass and Volume Relatlonshios ma%. vowm toy d sp,acementof wter), ength. mod amem of oram ana a1.m nm cylmders (a) Look for general relationships among variables. Meas-re
Plot mass versus volume foraluminum cylinders to see what type of relationships might exist. Develop an equation relating mass and volume, first by trial and error, then by determining slope and y-intercept and placing in the general equation for a straight line. (c) Plot mass versus volume for brass and performthe same type of analysis as for aluminum. (dl The concept of density is introduced. Application: (a) Use both the graphs and equations developed in "invantion" to predict either masses or volumes of aluminum or brass given the value for one of the variables. (b) Calculate volumes of metal cylinders tmm equation V = r r 2 h , compare values with those obtained by water displacement, and discuss possible reasons for differencesnoted. ClarrHieatlon of Chemical Substances by Physlcal Propeiiles Exploation: For eight solids determine approximate melting points; solubilities in water, polar organic, and non-polar organic solvents: conductivity in solid phase and in water solution (Instructor provided conductivity in molten state):and density far one substance (otherssupplied by instructor). (a) Classify the substances separately on the basis of Invention: similarities in melting paint, solubility, conductivity,and density. (b) Develop a general classitication scheme which groups substances with similar properties in all categories. (These classificationsfarm the basis for later discussion of the relationship between physical properties and bonding type in lecture.) Appficatton: Design a brief experiment to extend your knowledge of the physical properties of substances in s a w manner. Sample possibilities are "Does solubility of a'substance in water depend in any way on the temperature of the water?" and "Does the conductivity of a substance dissolved in water depend on lhe quantity ot lhe substance dissolved?" Colorimetry (a) Observe solutions d various colored salts and compare two solutions of a salt, one dilute and one concenhated. to note the difference in color intansitv. (b)
diameter and small diameter. Rank solutions according to color intensity. h ~ ~ n f i ~Look : tor relationships between color intensity and other variables. Application: (a) Use 'Wandards" prepared In the exploration phase to determine visuailv the a~oroximateconcentration of an
(b)
conditions are necessary fora fair comparison of unknown and standards. Determine the concentration of an unknown using a spectrometer afler the operation of a spectrometer is explain% briefly.
setnble a workhook in that they require the student r o a n s w r questims in writing as thry proceed through the expcrlmenr. 'I'his process not only rrqbires thar the student think ahout the data u,ltile working, but also it provide an opportunity for thr inaructgjr 111 interact with individualc as rhey a r t m p t to answer rhe quesrims. Students are generally ttrged tu complete the inventhm section, and as much ut the application ~ectitrnas possihle, while i n the laboratory a)that they can recewe assistance (in rhr form of lead~nrauestions) as needed. Thus, although most students have some remaining questions or protrlt.ms tocomplete on their own, thr majority of rhe required repmr i i finished lwft,re leaving the laharator!'. This approach has proven to be ~articularlysuccessful for students who have weak backgrounds, since they can receive assistance in analyzing the quanitative data. Such assistance, of course, becomes more difficult to obtain as the semester proceeds and the students acquire more experience. A SMODS~S of three tmical from the ". laboratorv- experiments . . general chemistry laboratory program a t Xavier is provided in Table 1.I t should be noted that althoueh their format is non-traditional, the content of each is typical of that in other eeneral chemistrv laboratorv proerams. A list of the entire sequence of expeknents is gi;en
