That sounds bad

[Buddabing]

Not really. Water can be heated above boiling but it becomes unstable.

Link

[ChadTower]

In the Why is it possible to heat water above its boiling temperature? the explanation is very, very similar to what I described.  It does say that the water can sit above 100c until that energy is released, but it doesn't say how far.  When it starts to give numbers they don't go above 101c and instead describe the amount of energy needed to accomplish that.  While 101c is technically superheated, it's still going to burn you less than steam at 100c because of the lower density of the liquid vs how much more surface coverage you get from steam.

[boykster]

Yep, 101c is about the threshold for superheating.  The damage/danger is less about it being "so hot" but more about the abruptness of the conversion from liquid to gas and the violence of the conversion.  Unlike a slow boil which builds gradually, its an instant one, converting a large portion of the water to steam in a very short period of time.

I don't know which would "burn more" -> the liquid water is much denser than the steam so would carry a much larger amount of heat energy per unit volume, but the steam could definately contact more surface area more quickly, but last a lot less time as it is more volatile and would be dispersing.

 

[ChadTower]

Is it converting all at once or are all of the disparate converted molecules suddenly finding each other and gaining enough volume to burst upwards all at once?

[Ed_McCarron]

Its all ready to boil.  Give it a start and a big chunk of it flashes to steam.  The wavefront moves through the water PDQ.  Its not instantaneous, but might as well be.  If the phase change didn't suck so much heat energy out of the water, it'd probably all convert.

[shmokes]

I'm no scientist, and my experiments are decidedly informal.  But I'm telling you, I heat up this water on a regular basis and it doesn't boil until I disturb it, but I never see it explode the way it does in that video, and the way it is described by people who have been injured by it.  I assume this is because I'm not getting it as hot.  Maybe it's because the thing I'm disturbing it with is a large block of ice, which causes such an abrupt temperature change that much less of the water suddenly boils.  In any case, there seems to be different levels of violence associated with the sudden boiling of superheated water, which led me to believe that some water was significantly higher than 100c degrees.

[Ed_McCarron]

I've actually had it happen.  Take a smooth, glazed mug.  Fill with water, then let sit in the microwave for 15 minutes because you forgot you were making tea.

Come back, turn on microwave for 3 or 4 minutes.

As soon as its done, drop in a teabag.  The burn has since healed, but I'd say at least half of the mug flashed to steam, and damn near the rest of the water splashed out at the same time.

Had a nasty burn on about half of my hand.  Hurt like a SOB for a week.

[ChadTower]

Moral:  don't teabag things without warning.