Topic: Hot water question
started by: askheaves
Which would burn worse:
Some water poured on your arm at 212 F or some steam blown on your arm at 212 F.
Make your assumptions, as this is about as much information as I remember from the question. Thank you for putting this haunting issue from my youth to pasture.
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Ah screw it.
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edit: my explanation was backwards, thanks SLATE 
This message has been edited by CatKnight on May 18, 2001 at 06:43 AM
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This message has been edited by CatKnight on May 17, 2001 at 07:50 PM
quote:
Originally posted by MattimeoZ80:
and water can't become as hot as steam no matter how hot it is.
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ok, i have the solution to this problem.
seeing as steam would never keep at the same temperature (unless it was the only thing in a vacuum or something). if the steam was at 212 degrees at the point when an object (like a fan or something) blew it towars youre arm, the steam would of dispearsed and thus would have become cooler.
but what if you threw water at your arm? yes, it would cool down. BUT, it takes a LOT of more energy to change the temperature of water than it does anything else (like metals or something)
So, water would hurt more.
(i know too much about some stuffs
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I may be paranoid, but not an Andriod.
And to correct that boiling water statement up there 
Water turns to vapor at 100°C (212°F?). It really does. But it's not all the molecules in the pot, that's this warm at the same time. The molycules in the buttom of the pot is heated first, thereby turning into vapor that bubbles up through the colder water
This message has been edited by miNus on May 18, 2001 at 05:38 AM
I think that it is steam that would burn more. Why? I don't know...
REASEARCHED:
quote:
Steam burns are more damaging than burns caused by boiling water because steam gives up additional energy when it condenses and has more energy per kilogram than boiling water.
from < http://www.physics.eku.edu/Ciocca/test3phy101.html >
quote:
It is a common knowledge that the burns caused by steam at 100 °C is more dangerous than the burns caused by boiling water at 100 °C. The reason can be explained if you consider the latent heat. When steam converts into water at 100°C, it gives off latent heat of 22. 5 105 J/kg. This extra energy causes more severe burns. In the same way, you might have heard the term cold “burn”. This happens when skin is exposed to very cold temperatures. The “burn” occurs because of the release of latent heat. Take a small piece of ice. Press within your fingers and see how your fingers will burn.
from < http://www.education.eth.net/acads/physics/heat-II.htm >
quote:
BUT, it takes a LOT of more energy to change the temperature of water
the specific heat of water does not depend on the phase
oh and SLATE, you're right! i had it backwards in my explanation. steam would burn worse because it has more energy due to heat of vaporization. btw, you can't see steam at all, it is a transparent gas just like all other gasses. what most people think of as steam, such as coming from a boiling pot, is actually water vapor.
I disagree though. I took an approach slightly outside of a physics/chem question. If you get hot water on you, you have a constant surface contact with a relatively thick layer of liquid. The heat that is transferred away from the water into your arm, and then is insulated by the water behind it... and being fed more heat. With steam, the contact is spread out over a larger area, and it's more spaced out. This gives the heat more directions to travel and burns less in a larger area.
That was my reasoning. Still got it wrong.
quote:If you had boiling water on your arm, would you just sit there and let it burn you?
Originally posted by askheaves:
I disagree though. I took an approach slightly outside of a physics/chem question. If you get hot water on you, you have a constant surface contact with a relatively thick layer of liquid. The heat that is transferred away from the water into your arm, and then is insulated by the water behind it... and being fed more heat. With steam, the contact is spread out over a larger area, and it's more spaced out. This gives the heat more directions to travel and burns less in a larger area.That was my reasoning. Still got it wrong.
Get a clue.
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quote:
temprature is the measure of the motion of molecules. pressure is the measure of collisions. same temprature and pressure = same 'excitedness' of the molecules.
if that is so, and knowing that pressure is inversly proportional to the volume, i would have to say that water would burn more because water has lower volume and higher pressure, while gas has high volume and low pressure. from this can be drawn a conclusion that water will result in more pressure then gas and therefore create a stronger sensation of pain.
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I agree it's a dumb question, but it's been popping into my head off and on for 6 god damn years. I need closure.
quote:
Originally posted by SLATE:
if you were 20 feet away, shooting someone with a ultra mega super soker 2billion with 212 degree water
NOTE TO SELF: Buy ultra mega super soker 2billion before mom visits...
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quote:
Originally posted by askheaves:
Water doesn't have a pressure. It's an incompressible liquid... like most liquids.
What a load of crap. Of course you can compress water. How do you think the pressure increases as you go deeper down? Every 10m down equates to approx an increase in pressure of an atmosphere.
Back to the question at hand... One thing that must be done first is to distinguish between steam and water vapour. What you can see coming off the kettle is water vapour. This is condensed steam. You can't see steam, as it is a COT gas (colourless, odourless, tasteless). If you want to test this for yourself, boil a pot of water. There will be a thin layer between the surface of the boiling water, and where you can see the water vapour. In this region is the steam.
Water vapour will burn you as good as boiling water, as it just is water. Steam will burn you more because as it comes into contact with you, it will lose energy, as you a colder than the steam, and the steam wants to get to thermal equilibrium with you. As it loses energy, it must go through a phase change, from gas to liquid. This is where the damage is done.
If, as the question stated, the steam is at 100C, there is no energy loss, and hence burning of your bodily parts associated with bringing the steam down to the boiling point of water. The burn is done by the latent heat of vapourisation; the energy associated with the steam changing phase.
Conclusion: Steam will burn worse than water.
But it also depends on the amounts involved. If you got dumped into a vat of boiling water you would be burnt more than if you stuck your hand over the spout of a kettle.
Also note, if you put your hand into boiling water, the water immediatley surrounding your arm will become cooler, and insulate your arm. This same principle allows you to roll liquid nitrogen around on you hand its fun and freaks people out )
In this reply, I have reiterated points already mentioned. I'm not stealing your glory, I'm just making my reply coherent. I think.
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