The study investigates the use of analog tasks for determining difficulties that high school chemistry students might encounter in solving molarity problems. Students (n = 619) from five schools completed three tests given throughout the school year. These were: an analog test, a molarity test, and a retention test. The analog task consisted of dissolving lemonade powder for solid sodium hydroxide. Results indicate that the analog task is a predictor of success on the molarity test; that difficulties encountered on the analog test are similar to those on the chemistry test, and that achievement on some types of chemistry problems might be improved by us in analog tasks in instruction.