In the case of a single substance (water), looking at the phase diagram is enough to conclude what happens upon heating:
(source: WolframAlpha)
But what if I have water and air (or some other gas) in the same sealed container? Would the air saturate at some point and prevent further water from turning into gas?
(Wolfram have a "Heating Water and Air in a Sealed Container" demonstration)
EDIT:
According to Wikipedia:
Superheated water is stable because of overpressure that raises the
boiling point, or by heating it in a sealed vessel with a headspace,
where the liquid water is in equilibrium with vapour at the saturated
vapor pressure.
But is there a quantification of this "equilibrium"?
Best Answer
You have a 2 liter rigid container, featuring 1 liter of liquid water and, above it, one liter of a mixture of air and water vapor all at 1 atm. The temperature is 20 C, and the partial pressure of the water vapor in the head space is the equilibrium vapor pressure, so that the system is at equilibrium. This is the initial thermdynamic equilibrium state of the system. Start out by determining the partial pressure of air in the head space, the mass of air in the container, and the mass of water. In the ensuing calculations, it is permissible to assume that the partial pressure of the water vapor in the head space is equal to the equilibrium vapor pressure at the liquid temperature and the air is not soluble in the liquid water.
Vapor pressure of water at 20 C = 17.5 torr = 0.023 atm
Partial pressure of air in container at 20 C = 0.977 atm
From ideal gas law, moles of water vapor in head space = 0.00096
Mass of water in head space = 0.017 grams
Total mass of water in container = 1000.017 grams
Moles of air in head space = 0.04066
Mass of air in head space = 1.18 grams
Now you raise the temperature of the system to 50 C and let it equilibrate. What is the partial pressure of water vapor in the head space, and the mass split between the liquid water and water vapor? And what is the partial pressure of the air in the head space? What is the total pressure.
NOW FOR 50 C
Vapor pressure of water at 50 C = 92.5 torr = 0.121 atm
From ideal gas law, mass density of water vapor in head space = 0.0822 g/l = 0.0000822 g/cc
Let x = mass of water in vapor phase
Mass of water in liquid phase = 1000.017-x
Volume of water in container (cc) = $(1000.017-x)+\frac{x}{0.0000822}=2000$
Solving for x : x = 0.0822 grams
Liquid water remaining = 999.93 grams
Volume of vapor = 1.00007
From ideal gas law, partial pressure of air = 1.077 atm
Total pressure = 1.197 atm.
Now try 100 C, 150 C, 200 C, etc.