Introduction: Crystallization (solidification) is the exact opposite of the process of fusion (melting). When a substance undergoes a phase change, heat is either released or absorbed by the substance. Crystallization involves a phase change from liquid to solid; heat is released by the substance as it solidifies. Crystallization, then, is an exothermic process. When the process of crystallization takes place in a calorimeter, the heat released by the substance that is solidifying is absorbed by the water in the calorimeter. As a result, the temperature of the water increases. The temperature change can be used to determine the heat of crystallization of the substance undergoing the phase change.

Purpose: The student will determine the heat of crystallization of a wax sample.

Materials: 25 x 200 test tube, 250 mL Beaker, Ring stand and ring, Hot plate, 100 mL Graduated cylinder, Thermometer, Styrofoam cup, Safety goggles, Wax sample, Balance, Test tube tongs

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