# Can water be heated until is is incandescent? **URL:** \ **Category:** Factual Questions\ **Created:** [August 30, 2007, 2:00pm UTC](https://boards.straightdope.com/t/can-water-be-heated-until-is-is-incandescent/417496 "2007-08-30T14:00:30Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [August 30, 2007, 2:00pm UTC](https://boards.straightdope.com/t/can-water-be-heated-until-is-is-incandescent/417496/1 "2007-08-30T14:00:30Z")
Can water be heated until it emits visible light? I realise it won’t be liquid anymore - at least not at normal pressures - but can it be done without breaking the molecular bonds? ---
**Author:** ![Szlater](https://avatars.discourse-cdn.com/v4/letter/s/90ced4/32.png) [@Szlater](https://boards.straightdope.com/u/Szlater)\ **Post date:** [August 30, 2007, 2:21pm UTC](https://boards.straightdope.com/t/can-water-be-heated-until-is-is-incandescent/417496/2 "2007-08-30T14:21:52Z")
Is [this](http://www.newscientist.com/article/dn9293-physicists-create-great-balls-of-fire.html) what you mean? > [@](#): > > “We therefore use a short, high-voltage discharge of 5000 volts to vaporise some of the water in a glass tank and create the plasma ball.” > > The tank contains two electrodes, one of which is insulated from the surrounding water by a clay tube. The high voltage causes enormous currents of up to 60 amps – over 200 times those needed to cause death – to flow through the water for a fraction of a second. These enter the clay tube, causing the water there to evaporate and a luminous plasma ball - consisting of ionised water molecules - to rise from the surface. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [August 30, 2007, 2:52pm UTC](https://boards.straightdope.com/t/can-water-be-heated-until-is-is-incandescent/417496/3 "2007-08-30T14:52:06Z")
[Breaking Water Down Into Constituent Elements](http://boards.straightdope.com/sdmb/showthread.php?t=331125): [QUOTE=Squink] [Water starts to dissociate](http://lassc05.chim.ulg.ac.be/hydrogen/therm.htm) into atomic and molecular hydrogen and oxygen at about 1800°K (2780°F). At low pressures, dissociation is complete above 3500°K (5840°F). [/QUOTE] Your steam will be glowing pretty good by the time it hits 2700 °F. ---
**Author:** ![matt](https://avatars.discourse-cdn.com/v4/letter/m/a6a055/32.png) [@matt](https://boards.straightdope.com/u/matt)\ **Post date:** [August 30, 2007, 2:57pm UTC](https://boards.straightdope.com/t/can-water-be-heated-until-is-is-incandescent/417496/4 "2007-08-30T14:57:51Z")
I don’t think water can be made incandescent in the sense of a hot black body emitter. When you burn hydrogen in oxygen, the flames are [invisible](http://adsabs.harvard.edu/abs/2005SPIE.5880..181F) but the flame product is gaseous H2O at 2000-3000 K depending on whether it’s burnt with oxygen or air. I find it hard to believe that **Szlater’s** “luminous plasma ball” literally consists of “ionised water molecules”. In a plasma the hydrogen and oxygen will be dissociated from each other, and the electrons are free so they can undergo non-quantised transitions and emit visible light. ---
**Author:** ![matt](https://avatars.discourse-cdn.com/v4/letter/m/a6a055/32.png) [@matt](https://boards.straightdope.com/u/matt)\ **Post date:** [August 30, 2007, 3:13pm UTC](https://boards.straightdope.com/t/can-water-be-heated-until-is-is-incandescent/417496/5 "2007-08-30T15:13:46Z")
This pdf, page 4, explains that H2O doesn’t have the correct energy levels to emit visible or ultraviolet light. It’s infrared all the way for water. [http://www.tempe.mi.cnr.it/zizak/tutorial/cairol06-flame-emission.pdf](http://www.tempe.mi.cnr.it/zizak/tutorial/cairol06-flame-emission.pdf) The UV given off in a hydrogen-oxygen flame comes from OH[sup]-[/sup] radicals. ---
**Author:** ![Szlater](https://avatars.discourse-cdn.com/v4/letter/s/90ced4/32.png) [@Szlater](https://boards.straightdope.com/u/Szlater)\ **Post date:** [August 30, 2007, 3:16pm UTC](https://boards.straightdope.com/t/can-water-be-heated-until-is-is-incandescent/417496/6 "2007-08-30T15:16:46Z")
[QUOTE=matt] I find it hard to believe that **Szlater’s** “luminous plasma ball” literally consists of “ionised water molecules”. In a plasma the hydrogen and oxygen will be dissociated from each other, and the electrons are free so they can undergo non-quantised transitions and emit visible light. [/QUOTE] That’ll teach me for not reading an article properly. > [@](#): > > John Abrahamson at the University of Canterbury, New Zealand, who proposed this theory, says that the luminosity produced by Fussmann’s lightning could be the result of clay and metal from the electrode being vaporised, leading to a glowing dusty suspension of fine particles. > > Fussmann disagrees. “Preliminary results indicate the cloud contains mostly ionised hydrogen and oxygen,” he says. “While there are traces of copper, these are negligible.” The same chap who claims that it’s ionised water molecules then says that it’s actually ionised hydrogen and oxygen, and some copper too. D’oh! ---
**Author:** ![vetbridge](https://avatars.discourse-cdn.com/v4/letter/v/b5e925/32.png) [@vetbridge](https://boards.straightdope.com/u/vetbridge)\ **Post date:** [August 30, 2007, 3:41pm UTC](https://boards.straightdope.com/t/can-water-be-heated-until-is-is-incandescent/417496/7 "2007-08-30T15:41:06Z")
[QUOTE=Squink] Your steam will be glowing pretty good by the time it hits 2700 °F. [/QUOTE] So, how long would you steep your tea at these temps? ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [August 30, 2007, 4:22pm UTC](https://boards.straightdope.com/t/can-water-be-heated-until-is-is-incandescent/417496/8 "2007-08-30T16:22:58Z")
[QUOTE=matt] This pdf, page 4, explains that H2O doesn’t have the correct energy levels to emit visible or ultraviolet light. [/QUOTE] From the pdf: > [@](#): > > None of the ordinary molecules which are the stable products of combustion, such as H2O, CO2, CO, O2, or N2 possesses electronic energy levels situated so as to enable these molecules to give spectra of appreciable strength in the visible or ultraviolet regions. Presumably an unappreciable strength is still larger than zero. I’ve looked, and can’t find values, but it’d be amazing if water at 2000°F didn’t have _some_ visual emissivity. **vetbridge** : Earl Grey, or Darjeeling? 🙂 ---
**Author:** ![Sunspace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sunspace/32/1250_2.png) [@Sunspace](https://boards.straightdope.com/u/Sunspace)\ **Post date:** [August 30, 2007, 4:25pm UTC](https://boards.straightdope.com/t/can-water-be-heated-until-is-is-incandescent/417496/9 "2007-08-30T16:25:37Z")
[QUOTE=vetbridge] So, how long would you steep your tea at these temps? [/QUOTE] 15.7 nanoseconds. It’s actually the milk that is the problem. ---
**Author:** ![minor7flat5](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/minor7flat5/32/258_2.png) [@minor7flat5](https://boards.straightdope.com/u/minor7flat5)\ **Post date:** [August 30, 2007, 5:00pm UTC](https://boards.straightdope.com/t/can-water-be-heated-until-is-is-incandescent/417496/10 "2007-08-30T17:00:51Z")
One interesting thing that does happen is that water will eventually reach its [critical point](http://en.wikipedia.org/wiki/Critical_point_(thermodynamics)). When I was a young lad studying boiler theory in a Navy school, I found it absolutely intriguing that, while the jump from 600psi to 1200psi in modern naval boilers was fine, you couldn’t just keep heating the water to get higher (and more efficient) pressures. Eventually you would hit 3200psi and your water would cease to be either liquid or gas. It was never explained to me what would happen then. I imagined that the steam plant wouldn’t like stuff that wasn’t quite water nor steam flowing through it. And what would the stuff look like? ---
**Author:** ![vetbridge](https://avatars.discourse-cdn.com/v4/letter/v/b5e925/32.png) [@vetbridge](https://boards.straightdope.com/u/vetbridge)\ **Post date:** [August 30, 2007, 5:00pm UTC](https://boards.straightdope.com/t/can-water-be-heated-until-is-is-incandescent/417496/11 "2007-08-30T17:00:53Z")
Mmmmm. A good Darjeeling, hold the moo.😉 ---
**Author:** ![matt](https://avatars.discourse-cdn.com/v4/letter/m/a6a055/32.png) [@matt](https://boards.straightdope.com/u/matt)\ **Post date:** [August 30, 2007, 6:16pm UTC](https://boards.straightdope.com/t/can-water-be-heated-until-is-is-incandescent/417496/12 "2007-08-30T18:16:23Z")
[QUOTE=Squink] From the pdf: Presumably an unappreciable strength is still larger than zero. I’ve looked, and can’t find values, but it’d be amazing if water at 2000°F didn’t have _some_ visual emissivity. [/QUOTE] Maybe you’re right. Hydrogen flames are apparently [visible in the dark](http://www.micro-vett.it/H2/ing/H2ing.html). Although since they are blue, there’s a good chance most or all of this is from the OH radicals in the flame rather than hot H2O. H2O absorption is shown [on this page](http://www.lsbu.ac.uk/water/vibrat.html) (scroll down for a graph). I’m under the impression that if it can absorb a frequency then it can emit that frequency, so some visible light should be emitted. But I have no idea what those absorbance coefficients imply with regards to visible light. ---
**Author:** ![WarmNPrickly](https://avatars.discourse-cdn.com/v4/letter/w/d78d45/32.png) [@WarmNPrickly](https://boards.straightdope.com/u/WarmNPrickly)\ **Post date:** [August 30, 2007, 6:34pm UTC](https://boards.straightdope.com/t/can-water-be-heated-until-is-is-incandescent/417496/13 "2007-08-30T18:34:37Z")
> [@](#): > > I’m under the impression that if it can absorb a frequency then it can emit that frequency, so some visible light should be emitted. Absorption and emition graphs often have some symmetry, but are not identical. I would not put much faith in this assumption. In this case the exitation would be thermal so only certain energy levels will become occupied. These energy levels may not be in the visual range. ---
**Author:** ![garygnu](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/garygnu/32/2924_2.png) [@garygnu](https://boards.straightdope.com/u/garygnu)\ **Post date:** [August 30, 2007, 6:47pm UTC](https://boards.straightdope.com/t/can-water-be-heated-until-is-is-incandescent/417496/14 "2007-08-30T18:47:35Z")
Are there any other common substances that share this inability to emit visible light when heated? What is it about water? ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [August 30, 2007, 11:33pm UTC](https://boards.straightdope.com/t/can-water-be-heated-until-is-is-incandescent/417496/15 "2007-08-30T23:33:36Z")
> [@](#): > > In this case the exitation would be thermal so only certain energy levels will become occupied. These energy levels may not be in the visual range. Water molecules will remain intact at temperatures high enough that a non-negligible portion of the blackbody spectrum is in the visible range. So I would expect that there would be at least some excitation of those modes. ---
**Author:** ![WarmNPrickly](https://avatars.discourse-cdn.com/v4/letter/w/d78d45/32.png) [@WarmNPrickly](https://boards.straightdope.com/u/WarmNPrickly)\ **Post date:** [August 30, 2007, 11:52pm UTC](https://boards.straightdope.com/t/can-water-be-heated-until-is-is-incandescent/417496/16 "2007-08-30T23:52:44Z")
Am I wrong in thinking that the amount of radiation being emited as a blackbody would be reduced by the non-black body emisions in the infrared? ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [August 31, 2007, 6:05pm UTC](https://boards.straightdope.com/t/can-water-be-heated-until-is-is-incandescent/417496/17 "2007-08-31T18:05:54Z")
Of course, water will incandesce if you get it hot enough. It has a slightly bluish color and would have a useable emissivity in the visible red. It doesn’t dissociate until well hot enough to glow at visible wavelengths. The talk about spectral emissions isn’t relevant in blackbody thermal emission. The critical point, above which temperature and pressure the liquid and gas states run together, is interesting. Right at the critical point, any value of density over a broad range is possible, and waves and ripples of density will meander about. Liquids slosh inside their containers, and gasses don’t - if you bring a container through the critical point of its contents, you will hear the sloshing get fainter and disappear. I have seen a beautiful little handheld demonstration device holding something - a refrigerant, maybe - whose critical point is between room temp and body temp. You see it act most amazingly as you warm it and wave it around. ---
**Author:** ![matt](https://avatars.discourse-cdn.com/v4/letter/m/a6a055/32.png) [@matt](https://boards.straightdope.com/u/matt)\ **Post date:** [August 31, 2007, 6:42pm UTC](https://boards.straightdope.com/t/can-water-be-heated-until-is-is-incandescent/417496/18 "2007-08-31T18:42:08Z")
[QUOTE=Napier] The talk about spectral emissions isn’t relevant in blackbody thermal emission [/QUOTE] Does everything and anything radiate as a black body when you get it hot enough? Why does a 2000 deg. C methane flame appear blue but a 3000 deg. C tungsten lightbulb filament appear yellow-white? If water has a useful emissivity in visible red, why do hydrogen flames appear blue? Definitely feeling I’m missing something here! ---
**Author:** ![WarmNPrickly](https://avatars.discourse-cdn.com/v4/letter/w/d78d45/32.png) [@WarmNPrickly](https://boards.straightdope.com/u/WarmNPrickly)\ **Post date:** [August 31, 2007, 7:26pm UTC](https://boards.straightdope.com/t/can-water-be-heated-until-is-is-incandescent/417496/19 "2007-08-31T19:26:59Z")
> [@](#): > > The talk about spectral emissions isn’t relevant in blackbody thermal emission. Except that a body with spectral emisions isn’t a black body. ---
**Author:** ![rowrrbazzle](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rowrrbazzle/32/414_2.png) [@rowrrbazzle](https://boards.straightdope.com/u/rowrrbazzle)\ **Post date:** [August 31, 2007, 7:40pm UTC](https://boards.straightdope.com/t/can-water-be-heated-until-is-is-incandescent/417496/20 "2007-08-31T19:40:04Z")
the critical point of benzene: [http://www.youtube.com/watch?v=79H2\_QVBMGA](http://www.youtube.com/watch?v=79H2_QVBMGA)