<Tr> <Td> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> </Td> </Tr> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> <P> An isothermal process is a change of a system, in which the temperature remains constant: ΔT = 0 . This typically occurs when a system is in contact with an outside thermal reservoir (heat bath), and the change will occur slowly enough to allow the system to continue to adjust to the temperature of the reservoir through heat exchange . In contrast, an adiabatic process is where a system exchanges no heat with its surroundings (Q = 0). In other words, in an isothermal process, the value ΔT = 0 and therefore ΔU = 0 (only for an ideal gas) but Q ≠ 0, while in an adiabatic process, ΔT ≠ 0 but Q = 0 . </P> <P> Isothermal processes can occur in any kind of system that has some means of regulating the temperature, including highly structured machines, and even living cells . Some parts of the cycles of some heat engines are carried out isothermally (for example, in the Carnot cycle). In the thermodynamic analysis of chemical reactions, it is usual to first analyze what happens under isothermal conditions and then consider the effect of temperature . Phase changes, such as melting or evaporation, are also isothermal processes when, as is usually the case, they occur at constant pressure . Isothermal processes are often used and a starting point in analyzing more complex, non-isothermal processes . </P>

The process in which the value of ∆u=0 is