Concept Learning versus Problem Solving: Revisited Barbara A. Sawrey University of California, San Diego, La Jolla, CA 92093 Problem solving has been a t the heart of freshman chemistry courses for many years. Student success in an introductorycbemistrycourse is usually judged by the ability tosolve numerical nroblems. In a recent article1 Nurrenbern and ~ i c k e r i n ~ a i kthe e d question: is the ability to solve problems eouivalent to understanding molecular concepts? Their answer was no; the ability to solve a numerical piohlem did not euarantee conceptual understanding of the molecular basis of the problem. This work and that of Yarroch2was done on relatively small classes. Further, the sample in the Nurrenbern and Pickering experiment was drawn from a heterogeneous student population that was not mainstream. For a homogeneous student population that is average or better than average, the distinction between ability to solve numerical problems and ability to do conceptual problems may have little practical significance, simply because the students are bright enough to do both well. Therefore, I have repeated the Nurrenbern and Pickering experiment with a larger, more uniform group of students at a well-known university. In addition, I have separately studied student success on conceptual vs. numerical problems for the top and bottom of the class in order to see if the effect disappears for the higher achievers. The issue addressed by this research is important because i t cuts to the core of our ideas about teaching freshman chemistrv. Manv instructors. mvself included, have believed (or hope& that teaching students to solve problems is equivproposed, alent to teacbine the concepts. If, as is now being.. . this axiomis nottrue, then b e allmust rethink our approach to chemical education. Method The test auestions used for this studv come directlv from The stoichi&etry t h e ~ u r r e n L e r nand Pickering problems were used as part of the first examination, and the gas law problems were used as part of the second examination, given in the first quarter of a year-long general chemistry course for science majors. In both cases the testa consisted entirelv of multiple-choice questions, and the traditional questionappeared immediatelr before theconcept question. The students in this course were predominantly (R4°c~ firstquarter freshmen. Nearly all students (94.5%) had one or more years of chemistry in high school. No conscious attemptwas made to change my teaching style or to incorporate more or less conceptual material during the course. Results Tahle 1 lists the overall student success rate for these questionsas well as thesuccess rates for the upper and lower 270; ot the class. Clearly, all the questions were discriminating and can be used td distinguish the top students in the class from everyone else. But of interest in this study is that even the good performers had difficulty with the concept questions.
' Nurrenbern, S. C.: Pickering, M. J. Chem. Educ. 1987, 64, 508.
Yarroch. W. L. J. Res. Sci. Teach. 1985, 22,449. 3Gabel, D. L.: Samuel, K. V.; Hunn, D. J. Chem. Educ. 1987, 64, 695.
Table 2 shows the breakdown of answers chosen by all students. Most chemistrv instructors will have little trouble understanding why the most common (though wrong) answers were chosen. The ability to relate the particulate nature of matter to mathematical problem sol\&g is definitely not a common occurrence in my class! The dramatic differences in student success on the two types of questions are statistically significant, as shown in Tahle 3. This significance does not disaDDeaI for the uooer end of the class. Even the best numerical&oblem solversperformed poorly on the concept auestions. This is not a new result.'-3 but the size and natuie of the population in this study leaves little room for doubt as to the oervasiveness of the affliction. Educators and textbooks have devoted a great deal of effort to improving the methods of teaching problem solving to students. I contend this has largely been successful hecause of how problem solving is viewed. Drill work has relied on the 100 most popular chemistry questions as a basis. Table 1. Rate ot Student Success
Gas Laws All Students Upper 27% ofclsssa
N
Conceptual Question
Traditional Question
285 77 77
31.23% 44.16% 14.29%
87.72% 96.10% 80.52%
Lower 27% of class' Stoichiomeby All Students 323 11.46% 66.25% 87 20.69% 90.80% Upper 27% of class Lower 27% of class 87 3.45% 45.98% 'me upper and lower 27% of me class refer to overall performance on the entire 25item multiple-choice exam.
Table 2. Percent of Students Chooslng Particular Answers to the Conceptual Ouestlons (Correct Answer In Bold Type) no
Stoichiometry Gas Law
(a)
(b)
(c)
(d)
0.9% 31.2%
0.6% 47.7%
11.5%
87% 8.1%
11.9%
answer 0% 1.1%
Table 3. Statistical Slanlficance QuestionsCompared
xZ
Level of Significance
188.68 49.60 67.76
