This unit on chemical energetics is one of 10 first year units produced by the Independent Learning Project for Advanced Chemistry (ILPAC). The unit, which consists of two levels, provides a clear yet detailed and thorough introduction to the topic. Level one extends ideas from previous courses, introduces and emphasizes the importance of Hess' law, and shows how enthalpy changes associated with chemical reactions are used to discuss the stability of substances and the likelihood of those reactions occurring spontaneously. Level 2 examines the energetics of bond formation in both covalent and ionic substances. Six experiments, exercises (with answers), pre- and post-tests, and numerous worked examples are provided. Additional material (including an experiment on applying Hess' law and description of a bond calorimeter) is included in appendices. Students completing this ILPAC unit assume a greater responsibility for their own learning and can work, to some extent, at their own pace. By providing guidance, and detailed solutions to exercises in the units, supported by the optional use of video-cassettes, the project allows students to study A-level chemistry with less teacher contact time than a conventional course demands. (JN)