The purpose of this article is to share a learning-cycle sequence of lessons designed to convey the particulate nature of matter through use of physical models and analogical thinking. This activity was adapted from Conceptual Chemistry, a long-running professional development program for teachers of grades 4-9. Conceptual Chemistry's approach is…

The author describes how he used to teach a unit on food webs and ecosystems using actual food webs as models. However, the models used by the author tend to be either too simplistic or too complicated for his students. A few years ago, he solved these problems by making up his own food web, complete with invented plants and animals. The model has…