Ardas Ozsogomonyan Skyline College San Bruno, CA 94066
An Application of Gagne's Principles of lnstrucfional Design Teaching the limiting-reactant problem
This paper describes the results of an experiment in chemical education carried out a t the University of California, Berkeley, during fall quarter, 1976 ( 1 ) . Subjects were a subgroup of students enrolled in Chemistry lA, the first quarter of a year-long general chemistry course. This subgroup consisted of students identified as underprepared on the basis of their low scores (zero, one, two, or three) on a pretest (see Table 1). 'l'hr primary gonl ad this study was t h ~development . and validi~tionot effcctioe individualized instructional muterials to teach somr major concepts of stuichiumrtry ~especiollvthe lin>itinr-reactant~rohlemlto under~mpuredstudrnti.'l'o this end, instructionaidesign criteria were formulated, tested, and refined until the desired goals were achieved. Stoichiometry was selected on the considerations that the topic is used throughout chemistry and that many Chem 1A students have difficulty in learning this topic. Moreover, there is a dearth of systematic investigations of instructional strategies that facilitate concept learning in chemistry in generd and in stoichiometry in particular. The decision to work with und e ~ p r e ~ a r e d s t u d e nwas t s prompted by the general concern exhibited toward this group by the community of chemical educators (2,3). Experimental Design .A prrtrst-posttrsl control group design was used i n this study ( 4 , p. I:{!. On the hasis oitheir Scores ('l'ahle I i. 197 out 1400 students u,hu took thr pretest wert: identiiied as underprepared. The mean p e t e s t score of this group was 12%; whereas, by comparison, that of the entire class was 75%. Comnletion or noncomoletion of hieh school chemistrv was not cmsidert~das a crit~.rionto idrntify the unrlrrprepared student?. Indeed. @LC< o f t h e students in this crouo - .had w m pleted one year df high school chemistry. Undernre~ared . . students (hut no others) received individual letters inviting them to participate in a "short experimental program run by the Berkeley Chemistry Department." They were told that "the program offered individualized instruction in stoichiometry" and would "take about twelve hours to complete." The letter ended with the statement: "It is possible that not all applicants can he accepted because of space limitation." One hundred and fifty students signed up for the propram. These students were randomly divided into two iroups of 75 each. One of thc,se was r;?nd
