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This is for a story line that I would prefer to be based on known science as much as possible.

Is there a known compound that can phase shift from gas to solid or liquid, or the other way around, in room temperature, when a relatively small amount of electricity is applied?

With "a relatively small amount" I am thinking of something like what can easily be obtained e.g. from an automobile battery.

Alternatively is there any thoughts on what such a compound could be based on? (In this case, instead of naming a compound I could use some description of how it was created.)

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  • $\begingroup$ By Joule effect some solid can melt. Are you looking for this? $\endgroup$
    – L.Dutch ♦
    Jul 15, 2017 at 16:45
  • $\begingroup$ Hi @L.Dutch, thank you for asking, but in this case I am looking specifically for things that can change from gas to solid/liquid, or from solid/liquid to gas. $\endgroup$
    – ravn
    Jul 15, 2017 at 16:53
  • $\begingroup$ What do you need to achieve? Do you really need exactly solid, liquid or gas? Wouldn't some exotic states of matter go, like the liquid crystals? By the way, if you allow temperatures slightly above room, then putting the water into microwave could go, as superheated water explodes even after a small disturbance, so attaching a small electrical engine may trigger the explosion. $\endgroup$
    – jaboja
    Jul 15, 2017 at 17:58
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    $\begingroup$ Why is water not sufficient here? $\endgroup$
    – Aify
    Jul 15, 2017 at 21:21
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    $\begingroup$ How about two separate compounds such as sodium azide (NaN3) and potassium nitrate (KNO3) which are both solids and are rapidly burned in an airbag to produce the nitrogen gas that inflates the bag? This is similar to a solid fuel rocket engine works. $\endgroup$
    – user100487
    Jul 16, 2017 at 2:29

2 Answers 2

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You can boil water with adequate voltage. The water offers resistance to the current. As with anything that offers resistance, the current will heat it up and eventually it will boil.

Here is a video of a person boiling water after making homemade electrodes out of razors.

https://www.youtube.com/watch?v=q2r0GMVAWyI

Getting a gas to condense back to a liquid by adding energy is a tall order.

Another option is technically not a phase change of a single substance, but a change of a liquid to a different gas and back again: electrolysis of water to constituent hydrogen and oxygen, then electrically catalyzed combustion of hydrogen and oxygen back to water.

You can electrolyze water (H2O) into hydrogen and oxygen gas by passing a current through it. enter image description here http://www.instructables.com/id/Separate-Hydrogen-and-Oxygen-from-Water-Through-El/

You can turn the hydrogen and oxygen gas back into liquid water, again by passing a current through it. The voltage at sufficient energy will ionize the gas into plasma forming a spark. The heat from the spark will catalyze the combination of hydrogen and oxygen back into H2O.

You can accidentally boil water with your electrolysis apparatus if you do not pay attention and you deplete the electrolyte. As you deplete electrolyte, resistance of the water increases and it heats up.

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  • $\begingroup$ I could use a Peltier-effect device (Cools one side, heats the other) to cause condensation of water which would then be collected at the bottom. Probably not particularly efficient, but neither is electrically boiling it. $\endgroup$
    – Andon
    Jul 15, 2017 at 21:03
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Without knowing why you want this, it's hard to give a proper answer. As Will mentioned, direct electric boiling is possible, and indirect condensation is also possible. It's incredibly inefficient and very slow.

Playing with the laws of physics gives you a much more rapid option, but with significantly more equipment needed.

Water turns to vapor when it boils, but ALSO at lower pressures. (Technically, it just boils at lower temperatures at lower pressures). So, you build a container that can change its interior volume. Put the water in when its "compressed" and then have it decompress. With enough of a pressure difference, the water will boil into vapor. Recompress, and it'll condense back into a liquid.

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    $\begingroup$ If you used a substance other than water (say...isopropyl alcohol) you could do it at much more reasonable pressures. Rubbing alcohol boils at ~86F at 1atmo which would be trivial to use electricity to heat up a container above this point (or cool it down again). Couldn't find good numbers on the pressure required (at room temp) to cause it to boil/liquefy but I imagine it would be pretty reasonable. $\endgroup$
    – Draco18s no longer trusts SE
    Jul 17, 2017 at 17:05

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