Hi! I have an idea for how to break the second law of thermodynamics, and I don't see where it cracks. I would really appreciate if someone could explain this to me. Kelvin-Planck statement of the second law: "No process is possible whose sole result is the absorption of heat from a reservoir and the conversion of this heat into work." Clausius statement of the second law: "No process is possible whose sole result is the transfer of heat from a cooler to a hotter body." This is my idea: It involves vapor-liquid equilibrium, which is a state where the rate of evaporation equals the rate of condensation on a molecular level such that there is no net vapor–liquid interconversion. Imagine a chemical substance in this state, so that for example 50 % of the substance is in liquid state, and 50 % of the substance is in gas state for a certain temperature at atmospheric pressure, to make it simple. The substance is in a completely isolated (hypothetically) container, and since the liquid has a higher density than the gas, they will naturally separate from each other. Once equilibrium is achieved, the liquid is separated from the gas by a wall (see attached drawing). To introduce this wall shouldn't have to cost any energy. This will result in that the substance is not in equilibrium anymore. Since the substance will strive to achieve equilibrium again, some of the gas in the gas part of the container will try to condense, which will reduce the pressure in this part of the container. In the liquid part of the container, some of the liquid will try to evaporate, which will increase the pressure in this part of the container. So now, can't you just let the two pressures power a generator? Let the gas power a generator through contraction, and let the liquid power a generator through expansion. Once equilibrium is achieved, and the pressure has equalized, you just remove the wall, and do the same thing over and over again. The energy that powers the generator would come from the thermal energy of the substance, so after each cycle you would have to heat up the substance a bit. Theoretically this could have an efficiency of 100%. But this clearly violates the second law. According to the second law, heat can't purely be converted into work (see the first statement above). So why doesn't this work? Grateful for response!