Say I want to put a bottle of water in the microwave and heat it up. How do I determine the pressure in the bottle as a relation to the temperature of the water? Assuming that there is a headspace of air between the liquid and the bottle cap. Is it dependant on the volume of the air space? ie. would a half filled bottle experince a greater pressure at the same temperature than a bottle that is 90% filled? I'm trying to use partial pressures, but I'm battling to find out how much of the water is turned into vapour at certain temperatures.