The introductory core activities in this trial unit, prepared for students in grades seven through nine of Australian schools, use indicators derived from flower pigments to provide a more convenient measure of acidity than taste. Students are offered choices among seven options after completion of the core: "How Acidic is That?"; "What Colour is That?"; "Soil Acidity"; "Dyeing to do Something?"; "Overcoming Acidity"; "Acids all About Us"; and "Living with Acids." In each option there are suggestions for investigations and some open-ended questions. Topics in the options include chromatographic techniques effects of acidity on plant growth, dyes and fluorescers, neutralization and stomach powders, corrosion, and the effects of acids on organisms (including digestion processes). The teacher's guide, an "overprinted" version of the student manual, lists the objectives of the unit, the needed materials, suitable references and aids, and the approximate pH values of common substances. Suggestions for teaching are made. A student record book has spaces for recording observations and includes response sheets for the diagnistic tests included with most options. (AL)