What does entropy measure in a system?

Entropy is fundamentally a measure of disorder or randomness in a system. In thermodynamics, it reflects the number of ways a system can be arranged, which correlates to the degree of uncertainty or chaos present in that system. High entropy signifies a more disordered state, where energy is more evenly distributed, while low entropy indicates a more ordered state with less energy dispersal.

Using this understanding, the concept of entropy helps illustrate why systems tend to evolve toward thermodynamic equilibrium, where disorder increases, leading to a natural progression of energy states and arrangements. This behavior underpins many scientific principles, including the second law of thermodynamics, which states that in an isolated system, the total entropy can never decrease over time.

In contrast, other options discuss different aspects of thermodynamic processes. For instance, the amount of energy transferred in a reaction pertains to enthalpy, while the order and structure of a molecule relates more directly to molecular chemistry and bonding rather than entropy. Temperature stability in a chemical process relates to thermodynamic equilibria but does not encompass the concept of randomness or disorder associated with entropy directly.