Student Exploration: Feel the Heat Vocabulary: calorimeter, conductor, controlled experiment, dissolve, endothermic, exothermic, insulator, solute, solution, solvent, surroundings, system Prior Knowledge Questions (Do these BEFORE using the Gizmo.) Eduardo hurts his knee during a basketball game. The trainer applies a cold pack, which gets cold after being squeezed. The next day, Eduardo’s friend Beth is going sledding. Beth buys some hand warmers and puts them into her gloves. All morning, her hands stay toasty warm. 1. How do you think these devices work? 2. Where do you think the “cold” and the heat comes from? Gizmo Warm-up As you saw with the instant cold pack and the hand warmers, some reactions absorb energy while others release it. In the Feel the Heat Gizmo, you will explore these energy changes while making your own hot and cold packs. To begin, select the TEST POWDERS tab. Drag a bottle of NaC2H3O2 (sodium acetate) from the shelf. Using the sliders, decide how much water and powder to add. Note the beginning temperature, and then press Play ( ) to see what happens. 1. Did the temperature go up or down? 2. Experiment with different powders until you find one that produces the opposite effect. What powder did you use? There are more than likely 2 solutions inside the packets. When squeezed, it breaks the inside containers combining the solutions and creating either an endothermic reaction for a cold pack or an exothermic reaction for a heat pack. For the endothermic, when the substances mix, the reaction absorbs all the heat inside the container, dropping the temperature of the packet. For the exothermic, when the substances mix, the reaction gives off heat, raising the temperature of the packet.