What does entropy measure in a system?

Entropy is a fundamental concept in thermodynamics and statistical mechanics that quantifies the degree of disorder or randomness in a system. It reflects the number of possible arrangements of particles within that system—essentially how spread out the energy is among the available microstates. A high entropy value indicates a state of greater disorder and a larger number of arrangements, while lower entropy suggests a more ordered state with fewer possible configurations.

In the context of the second law of thermodynamics, systems tend to evolve towards states of higher entropy over time, reflecting a natural inclination towards increased disorder in isolated systems. This concept is crucial for understanding processes such as the direction of chemical reactions and the flow of energy, as systems will favor configurations that allow for increased entropy. Thus, measuring entropy serves as an important means of describing the level of disorder in a system.