Chemistry means more to students if you can tie it into their lives. It's hard to do that with a unit on gram formula weight and molar masses, but this will do the trick! My students loved (liked?) this short take home project and it generated a lot of class discussion about all those chemical in processed foods.
This worksheet has students tape or glue on the ingredients list of a processed food, highlight the components that are not food and then do a bit of research to find the formulas and calculate the molar mass or gram formula weight of 3 of the components.
Keywords: molar mass, empirical formula, covalent, ionic, chemistry