A thermodynamic process in which the temperature of the gas is held constant usually by connecting the system to a bigger system that has a much higher heat capacity, known as a heat reservoir. Heat or volume is changed very slowly so that the other properties could adjust while leaving temperature essentially constant — any small changes in temperature would be immediately eliminated by doing work, leaving no change in internal energy (; first law of thermodynamics).
When the temperature is constant, the product is also constant throughout the process. Note that the produce is constant but not the individual variables themselves.
Doing Work
Like an isobaric process, isothermal processes can do pressure-volume work.
Thermodynamic Properties
An isothermal process has the following properties:
since the energy of an ideal gas depends only on its temperature (obtained from definite integral above)