Sub-Zero

Chemical reactions can be described as endothermic or exothermic depending on whether energy is used or given off during a reaction. Practically, these types of reactions can be used as instant hot or cold packs at times when we need them, such as in hand warmers. In this task, students will be assessed on their knowledge of chemical reactions and energy change during the reactions. They will use molecular models to diagram the change in the arrangement of atoms and number and types of bonds before and after reactions. Following experiments where they measure the change in temperature of the reactions, students create models showing the change in energy (bond energy and thermal energy) in addition to the changes in the chemical species and number and types of bonds. Finally, students compare theoretical values for the temperature change of the reaction (given different reactant amounts) with their measured values using graphs and equations for lines of best fit and make evidence-based claims for whether the reactions they tested would be useful in hand warmers given criteria related to safety and usability.