Thermochemistry is a branch of chemistry that studies the heat energy involved in chemical reactions and physical changes. It focuses on how energy is absorbed or released during these processes, helping scientists understand the energy changes that occur when substances react or change states, such as from solid to liquid. In thermochemistry, key concepts include enthalpy, which measures the total heat content of a system, and calorimetry, a technique used to measure heat changes. By analyzing these energy changes, researchers can predict reaction behavior and design more efficient chemical processes in various fields, including industrial chemistry and biochemistry.