All materials have properties that are determined by their underlying structures. Materials are grouped according to different properties. Learners study the ideas that scientists have about the structures of materials. They investigate the properties of materials; how the properties change; and the effect of changes on the usefulness of materials. They interpret data on factors, which affect the rate at which materials react. The key concepts of the Natural and Processed Materials strand are: (i) the properties and structures of materials are interrelated, (ii) patterns of interactions between materials can be identified and used to predict and control further interaction, and (iii) the uses of materials are determined by their properties, some of which can be changed under certain conditions.