A comparison of student-directed and teacher-directed modes of instruction for presentation of density to high school chemistry students

The purpose of this study was to determine whether the mode of instruction makes a difference in the success of students as they structure a concept that is typical of the concepts students must understand in order to be successful in high school and college chemistry. The concept selected is density. Density contains two abstract critical attributes, mass and volume, and a proportional relationship between them. It is, therefore, a prototype for other important concepts in beginning chemistry. Instructional units were prepared in which the focus of the progress of instruction was either under the control of the students or of the teacher. The units consisted of five days of instruction. The content for each unit was the same. The subjects were in nine classes in two schools. Instruction was monitored daily by short criterion referenced quizzes. Over-all effect of the mode of instruction was measured by open ended surveys administered immediately before and after instruction. In-depth analysis was provided by structured interviews completed by thirty-two subjects the week after instruction. Effects of the mode of instruction over time were measured using problems completed several months after the experiment. These problems required the use of density to solve. They were contained in the units of solution chemistry and gas laws. Results of quantitative analysis of all measures showed that the influence of the teacher was more important than was the mode of instruction. Qualitative analysis of written and verbal responses made by subjects on dependent measures instruments showed the ability to understand mass and volume and the ability to use proportional reasoning were critical to development of a powerful construct for density. Despite previous exposure to density in school science courses and instruction received in this experiment, no subject demonstrated a construct that was as powerful as that held by scientists.