In a powerful illustration of colligative properties, students determine the molar mass of a substance by freezing-point depression. Students first identify a pure solvent's freezing point, dissolve their sample in the solvent, and determine the freezing point of this solution. The freezing-point depression is then used to calculate the molar mass of the sample. All kit materials are reusable so the experiment can be repeated multiple times. Kit includes a test tube rack for easy storage of freezing-point samples. Materials are sufficient for 30 students working in pairs.