Hello everyone, These days i am studying thermal physics in my classes so had a few queries to get clear about. The Kelvin statement says: “ No process is possible in which the sole result is the absorption of heat from a reservoir and its complete conversion into work. ” Yet the isothermal expansion is possible, i.e., all the heat supplied to the system by its surroundings get completely converted to work. And Wikipedia explains this as : Note that it is possible to convert heat completely into work, such as the isothermal expansion of ideal gas. However, such a process has an additional result. In the case of the isothermal expansion, the volume of the gas increases and never goes back without outside interference. So can someone please explain how is this isothermal possible still following the second law? Also please tell me if there is any restriction to the isothermal compression of a gas by the second law? Waiting for your reply..