Final answer:
Entropy change is a fundamental concept in thermodynamics that describes the dispersion of energy in a system and is crucial for understanding energy efficiency and the direction of natural processes.
Step-by-step explanation:
Entropy change in thermodynamics is a core concept that helps understand the second law of thermodynamics. The change in entropy (ΔS) for a process can be calculated using different approaches, depending on the specifics of the process—whether it's isothermal, adiabatic, or involves heat exchange with the surroundings. For example, in a reversible isothermal expansion of an ideal gas, ΔS can be computed using the formula ΔS = nRln(V2/V1), where n represents the number of moles, R is the universal gas constant, and V1 and V2 are the initial and final volumes, respectively. In the context of a Carnot engine, the entropy change for the hot and cold baths can be derived from the heat transfers (Qh and Qc) and their respective temperatures (Th and Tc), using ΔS = Q/T for each reservoir. The study of entropy is pivotal in understanding how energy is dispersed in physical systems and is critical in calculating the efficiency of heat engines and refrigerators. Entropy also provides insights into the directionality of natural processes, indicating why some processes are irreversible in the macroscopic world.