I was wondering and arguing (pro) with a friend that the process of water boiling is an excitation. I based my opinion on the theory that excitation is an increase in the energy level of an atom.

I also consider the heat supplied by the burner to be responsible for an increase in the thermal energy which in turn increases the kinetic energy of the atoms.

I want to know if my assumptions are correct or there is something I am missing or maybe I have the whole thing wrong.

  • $\begingroup$ Frankly, the process of boiling water tends to bore me... The proportion of atoms/molecules in an excited state, while a function of temperature, does not increase significantly from room temperature to 100C. $\endgroup$
    – Jon Custer
    Feb 22 '16 at 23:40

I based my opinion on the theory that excitement is an increase in the energy level of an atom.

Yes, boiling water introduces extra energy at an inter-molecular level (which, in everyday materials such as water, don't have discrete "energy levels" in a macroscopic sense), but the increase in "energy level" is:

$$\Delta E \sim \frac{3}{2} k \Delta T$$

For $\Delta T\sim100$K, this equates to 48meV. For comparison, "energy levels of an atom" (electron transition energies) are on the order of 10eV (an equivalent "temperature" of about 77000K).

The main problem with describing this as an "excited state" is that this phrasing implies that the system (the pot of water) can be described as a discrete set of energy levels, like energy levels in hydrogen, while instead you will have a distribution of energy levels centered around the mean temperature in the pot of water given by the Boltzmann distribution.


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