Entropy (S) is best described as:

• A. Disorder or randomness of a system
• B. Internal energy per mole
• C. System volume
• D. Thermal conductivity

Answer: (A)

Entropy is about how energy is spread among the microscopic configurations of a system. It measures the number of ways the molecules and their energies can be arranged at a given macrostate, so higher entropy means greater microscopic disorder or randomness. This makes the option describing entropy as disorder or randomness the best fit, since it directly reflects the spread of energy and the number of accessible microstates.

Internal energy per mole describes how much energy the system contains, not how it’s distributed. System volume is a geometric property of the container, not a measure of energy distribution. Thermal conductivity is a transport property that tells you how easily heat flows, not the thermodynamic state of the system. Remember, entropy is a state function tied to the distribution of energy among microstates, and it tends to increase when energy becomes more dispersed.