The Chemistry of Cold Packs is a new TED-Ed chemistry lesson. In the short lesson students learn how those cold packs, prevalent in every high school athletic trainer's kit, go from room temperature to near freezing so quickly. The lesson includes explanations of exothermic and endothermic reactions. The questions that follow this lesson are a bit more detailed than those found at the end of many other TED-Ed lessons. The video is embedded below.