Can a liquid be heated passed its boiling point before converting to its gaseous form? I'm not referring to changing the pressure (suppose we fix the surrounding pressure). Water boils at 100 deg C, but I guess I'm looking for clarification about how this happens. Does the water inside (the parts of the liquid that are not at the border of surrounding gas) surpass 100 deg C? I guess I'm just looking for clarification since it's been some time since I've taken chemistry/thermodynamics and was curious. Is it the water molecules at the edge of surface that will turn to gas once they hit 100 deg C? Are the water molecules in liquid form slightly higher "inside" the liquid?

I was looking at this article: https://en.wikipedia.org/wiki/Superheating and was curious about the statement for "Cause" where it states: "For the bubble to expand, the temperature must be raised slightly above the boiling point to generate enough vapor pressure to overcome both surface tension and ambient pressure."

Thank you!


1 Answer 1


Yes it can. It is one of the reasons why, performing a distillation, you gently stir the liquid in the lower round bottom flask.

If you distill under reduced pressure, superheating of liquids is even more prominent so that you may add boiling chips to the (still cold) stirred liquid, or that you rotate the flask containing the mixture from which you want to remove e.g., the solvent of reaction with a rotary evaporator

enter image description here

(image credit: Wikipedia).

In the later case, the distillation no longer occurs from the bulk of the solvent, but from the thin film of the liquid on the inner wall of the rotating round bottom flask.

  • $\begingroup$ That's certainly a device, thanks for the response. Follow up question: In a standard beaker, if heat is being applied at the bottom, when the water hit's a full boil, is there any part of the water in the center of the fluid's body that is hotter than 100? Or the water molecules nearer to the flame, would they ever go over 100 and remain in liquid form in the beaker. I know the heat would distribute, and the water at the surface would begin to evaporate at 100 (again, 1atm pressure). Does water being surrounded by other water keep it in liquid form despite being hotter than boiling pt? $\endgroup$
    – F4G4opener
    Feb 10, 2023 at 3:50
  • $\begingroup$ The device is an older one some (teaching) labs not exchange for more modern ones e.g., this one, or this one because of the price tag. For temperature, you need multiple molecules (Boltzmann distribution of energy) because a single molecule only has its own energy. Boiling includes energy corresponding to a temperature plus surpassing latent enthalpy of vaporization. $\endgroup$
    – Buttonwood
    Feb 10, 2023 at 8:31
  • $\begingroup$ You can not form a liquid with only one, or two, or three molecules; a liquid is an ensemble (at leas to form a droplet). Within a beaker, a molecule close to the heating plate at the bottom surely can accumulate more energy than molecules close to the upper surface, but to enter the gas phase, it has to travel up (against hydrostatic pressure) and beyond the surface (surface tension). Bouncing with other molecules, energy is exchanged with them (i.e., the energy can drop below the critical threshold, it can "cool down"). A bit like vents. $\endgroup$
    – Buttonwood
    Feb 10, 2023 at 8:37

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