Which branch of thermodynamics uses probability theory to study microscopic behaviors?

The branch of thermodynamics that employs probability theory to analyze the microscopic behaviors of particles is Statistical Thermodynamics. This field focuses on how the properties of large ensembles of particles can be related to the behavior of individual particles using statistical methods.

In Statistical Thermodynamics, various configurations of the microstates (the specific arrangements of particles) are considered, and the likelihood of each configuration is examined to derive macroscopic properties, such as temperature, pressure, and entropy. This approach is particularly useful for understanding systems with a large number of particles, where individual particle dynamics might be too complex to study directly.

This method provides deeper insights into thermodynamic laws by bridging the gap between the microscopic nature of matter and the macroscopic observables, allowing for predictions about the behavior of gases, liquids, and solids at different temperatures and pressures. It is this connection to probability and statistical methods that distinctly characterizes Statistical Thermodynamics compared to other branches.