This is a volume in the "Nuffield Co-ordinated Science" series, a scheme designed for fourth and fifth year secondary school pupils. It enables the student to follow a broadly based science scheme, emphasizing the links between the different branches of science, but providing separate textbooks for biology, chemistry and physics. The complete course consists of five pupils' books, activity sheets to accompany them and a single teachers' guide. This study concentrates on chemistry, discussing the skills and processes of science as well as the pure knowledge content. The book introduces the main ideas by developing them in contexts that are familiar to the reader, and stresses the industrial, economic, environmental and social impact of science. The contribution made by distinguished men and women to the development of scientific ideas is also described.