Exploring Energy Changes: Designing Heat & Cold Packs in Chemistry Lab

In a recent lab, AP Chemistry students investigated how chemical reactions involve energy changes. These energy shifts occur when reactants rearrange to form products, either releasing (exothermic) or absorbing (endothermic) heat. While students can’t directly observe these energy changes, they can measure their effects on the environment using calorimetry—specifically, how the temperature of water changes during a reaction.

Students applied the concept of enthalpy (ΔH), which represents heat energy at constant pressure, and used the equation Q = m * ΔT * cₚ to calculate heat transfer. They explored how different compounds dissolve in water and whether their heat of solution (ΔHsol) makes them suitable for use in heat or cold packs.

As part of an engaging challenge, students acted as researchers for "CHEMPACK Inc.," tasked with designing an effective, non-toxic heat or cold pack. They tested various compounds, analyzed temperature changes, and determined the best candidate for the product. This culminated with a "trial run" of their chemical pack that needed to meet specific criteria.

This hands-on experience reinforced key thermodynamics concepts while allowing students to apply their learning in a real-world context!