The title really says it all. How hot can steam (gaseous form of water) be before it ceases to be steam. I'm assuming that at some point the molecular bonds will give way, though I might of course be wrong.

Edit: I did try and search online but most places seem to talk about how hot you can get steam in engines and similar. I have only found one very strange quora post that seemed to imply temperatures in the range of 100 000K which seemed iffy to me.

  • $\begingroup$ Thermal decomposition of water. Search also for water dissociation temperature. $\endgroup$ Jun 26, 2022 at 19:44
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    $\begingroup$ My superheated steam tables go up to 1300 C $\endgroup$
    – Bob D
    Jun 26, 2022 at 19:48

1 Answer 1


If you can manage to get the steam sample up to about 3000 C, roughly half of the water molecules in it will have split apart into oxygen and hydrogen, and won't be water anymore.

  • $\begingroup$ That's interesting. Applying the $\bar K=1.5kT$ approximation from kinetic theory comes out to considerably less than the $\Delta H$ for water. Am I making a bad assumption by expecting the values to line up? $\endgroup$
    – g s
    Jun 26, 2022 at 20:01
  • $\begingroup$ I don't know! -NN $\endgroup$ Jun 26, 2022 at 21:39
  • $\begingroup$ Water should be 3x that (I forgot to account for rotational and vibrational degrees of freedom) but average kinetic energy still ends up only about 20% of the enthalpy of reaction. I'll pose a separate question. $\endgroup$
    – g s
    Jun 27, 2022 at 17:36

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