JCE Classroom Activity #112: Guessing the Number of Candies in the Jar—Who Needs Guessing?

Converting among different units, for example between grams and moles or among the different number of moles of substances in chemical reactions, is an important technique throughout general chemistry in high school and college. Such conversions rely on the simple idea of proportional reasoning, which students probably first encounter in grade school. However, providing a conceptual basis for proportional reasoning in chemistry can be difficult, because units such as moles and atoms are abstract and unobservable. Introducing proportional reasoning to students using a visible and engaging activity provides the opportunity to make the concept clear to students prior to using proportional reasoning in more abstract work. This Classroom Activity uses a popular giveaway game, guessing the number of candy pieces in a jar, to accomplish this goal. At the same time, it introduces students to the idea that different units and types of measurement, such as counting and mass, can be used on the same sample. The acti...