The Salters' team at the University of York believes that science teaching should be founded on materials and experiences familiar to pupils. Key scientific concepts are drawn out from contexts which really mean something to pupils. For example, using shampoos as a starting point leads to the need to consider acids and alkalis; drinks provide the context for the particulate theory; monitoring a premature baby introduces aspects of information technology. This is the second of four textbooks in a Key Stage 4 course. The structure of each chapter aims to reflect the ways in which students use their textbooks - for revising, for reference, for homework and so on. A corresponding unit guides pack for teachers is also available.