In the discussed experiment, it is clarified that internal energy can remain unchanged during expansion only under isothermal conditions, while adiabatic expansion or heat loss can alter this. When expanding into a vacuum, no work is done and, consequently, internal energy and temperature remain constant for an ideal gas. Joule's experiment confirmed that for ideal gases, internal energy is solely a function of temperature, resulting in no temperature change during specific conditions. However, for real gases, this relationship is more complex and varies slightly. The discussion also touches on the implications of conducting endothermic reactions adiabatically, questioning whether temperature would drop in such scenarios.
