For a system in an isothermal process, what remains constant?

In an isothermal process, the defining characteristic is that the temperature of the system remains constant throughout the process. This means that no matter what changes occur within the system—such as changes in pressure, volume, or even entropy—the temperature does not fluctuate.

This type of process is significant in thermodynamics, especially in the analysis of ideal gases. According to the ideal gas law, for a given amount of gas at constant temperature, any increase in volume must be accompanied by a decrease in pressure, and vice versa, in order to maintain equilibrium.

While pressure and volume may change during an isothermal process, the constancy of temperature is crucial because it allows for predictable behavior and calculations based on the laws of thermodynamics, specifically those involving heat exchange and work done. Entropy may also change depending on the specifics of the process, but it is the temperature that is specifically held constant in an isothermal situation.