The use of molecular models to illustrate and explore phenomena in chemistry teaching is widespread. However, only one type of model is usually used, and not enough emphasis is put on its meaning. The advantage of computerized molecular modeling (CMM) stems from the convenience and simplicity of building molecules of any size and color in a number of presentations. To expose chemistry teachers to the use of CMM we developed a 14 h workshop on models. It consists of an introduction to the model concept, using various types of models (including CMM) and experiencing ways to use them for illustrating chemical structure and bonding via team projects. This workshop has been incorporated into pre- and in-service training at the Department of Education in Technology and Science at the Technion since 1994. As a final project, teachers were asked to plan a session of 1-2 lessons by building a miniature database of molecules along with working instructions. The new methodology is based on using CMM through a special booklet, designed in a constructivist approach. During 1995, it was implemented in three tenth grade experimental classes with two other classes serving as a control group. Overall, teachers' attitudes toward using molecular modeling to improve chemistry teaching were favorable. The effect of using molecular modeling on students' understanding and constructing new concepts was investigated in relation to chemical structure and bonding as well as to geometric and symbolic representation. In two representative questions related to three-dimensional molecule structure, the experimental group performed better than the control group. Students' attitudes toward the use of CMM have also been found to be positive. Most of the students enjoyed using the new methodology and indicated it helped them understand concepts in molecular geometry and bonding.
