During the period 1984-1986, over 30 teachers from the Yorkshire (England) region have worked in collaboration with the Children's Learning in Science Project (CLIS) developing and testing teaching schemes in the areas of energy, particle theory, and plant nutrition. The project is based upon the constructivist approach to teaching. This guide addresses the particulate theory of matter. The document is divided into two main sections, an introduction which gives a background of the topic and describes some of the classroom strategies which may be useful, and the "Scheme in Action," a lesson by lesson account. The "Scheme in Action" is divided into six parts, with each part including: (1) the intentions and underlying theory; (2) the action plan; (3) how to coordinate the activities in the guide; (4) reflections on each part; and (5) practical details and worksheets (where appropriate). (TW)