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Demian*
Oh Lordy, Plegaleggole
Thu 7th Aug '08 2:45PM
4678 Posts
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7th Apr '03
How hot do you think water gets?

I remember once refusing to hold my thermometer in boiling water any more after my science teacher had promised me it would stop at 100 and it had already reached 103. Of course, it was probably due to impurities in the water but I didn't know that, so I didn't feel too bad in detention that evening.

However, scientists have just discovered some at 407 degrees C, and it has previously been measured at 433!

http://news.slashdot.org/article.pl?sid=08/08/05/208224
  

Agentgonzo
There's no pee in catheter!
Thu 7th Aug '08 3:34PM
811 Posts
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8th Aug '06


Demian was bold enough to comment:
Of course, it was probably due to impurities in the water


Actually, it's more likely to be an improperly calibrated or (no offence) poorly used thermometer.

Mass produced thermometers are only accurate to a few degrees anyway, and I assume that you were using the standard lab glass alcohol/mercury ones.

These types of thermometer should also have a "submerge to" line on them where you immerse them in the liquid up to that line. The (in your case) boiling water will heat the bottom bulb of the thermometer and the liquid within up to the temperature of the surrounding water, but as the liquid goes up the thermometer, it hits the cooler glass and cools to (roughly) room temperature. If you submerge too far, too much of the thermometer is heated to the temperature of the water which in turn makes the alcohol inside expand more than it should leading to a higher reading. The same is true if you leave the thermometer submerged for a long time - convection causes the glass to heat up - or in a hot environment (like my mash-tun).

I've managed to read 110C off one of my thermometers by doing this before.
  

Demian*
Oh Lordy, Plegaleggole
Fri 8th Aug '08 9:02AM
4678 Posts
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7th Apr '03
Aha - that explains a lot! I was mainly concerned due to the fact that the scale seemed to stop at 107 and I therefore assumed it would explode in shower of flying glass and poisonous metals. Hey, I was 13 at the time
  

Spanners*
Misses his big brother :(
Sat 9th Aug '08 3:59PM
4597 Posts
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7th Apr '03
Well water itse'f is just a normal chemical which can get to a couple of thousand degrees before it's blasted apart into hydrogen and oxygen. It's boiling point is 100 degrees at normal atmospheric pressure but it raises propertionally with pressure.
There are deep sea vents where geothermal activity can heat water to over 400 degrees but due to the pressure at that depth it stays in liquid form.
    

General*
Windows Bob - the best!
Sat 9th Aug '08 9:39PM
4213 Posts
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7th Apr '03
In a pressure vessel water can get up to very high temperatures and stay liquid. It gets interesting if the vessel bursts because all the liquid instantly becomes steam as demonstrated by Adam and Jamie

    

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