This in-class activity is intended to help visualize the meaning of the subscripts and coefficients in molecular formulas that appear in balanced chemical equations. It has been my experience that students in 2nd semester general chemistry can sometimes still be confused about this fundamental aspect of chemical language. It substitutes edible candy for the atoms in a molecular model kit, thus allowing students to eat the atoms at the end. (My philosophy is that if students are eating, they're probably awake and could be learning!)
Upon completing this activity, students should be able to explain the difference between the coefficient in front of a molecular formula in a balanced chemical equation and the subscript after a particular atom in a molecular formula. They should also be able to solve stoichiometry and related problems involving the coefficients and subscripts of a molecular formula.
various colored m&ms (see implementation)
small plastic or paper cups (see implementation)
plastic spoons (if needed)
I implemented this activity in Fall 2011 with a group of 20 students sitting in groups of 4. Specific colored m&ms were procured at the party store so that the colors would match the colors of atoms used in molecular modeling but one could adjust the colors in the worksheet to correspond to the colors of m&ms found in a regular mixed bag (could be sorted by the instructor or by the students). The little cups for holding the m&ms were small plastic souffle cups (http://www.cometsupply.com/mp/SOLO+CUP/pm/SCCB200N/r/ga/) but paper condiment cups (like for ketchup) could also be used.
I didn't particularly worry about the students touching the groups' m&ms with their hands before they ate them but one could hand out plastic spoons for moving m&ms if this was a concern.
This activity would probably require some personal expenditure on part of the instructor to secure the materials.