This unit on the mole is one of 10 first year units produced by the Independent Learning Project for Advanced Chemistry (ILPAC). The unit, designed to help students consolidate some of the ideas about the mole learned in previous courses, consists of two levels. The first level focuses on: (1) relative mass; (2) the concept of the mole as the unit amount of substance; and (3) the use of the mole concept in stoichiometric calculations to determine how much material is used in a chemical reaction and how to find the empirical formula of a compound. The second level extends the concept of stoichiometry to reactions in solution, showing how to apply it in a variety of titrations. Five experiments, practical exercises involving the weighing of coins, and detailed notes on study skills are included. 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)