Miata Mailing List: February 2000, Message #107

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I would like to quote my physics book:

"Water heats so well in a microwave oven that you might be able to heat a
cup of water as much as 8 degrees C above the normal boiling temperature of
water //without causing it to boil//. If you then pour coffee powder, or
even chips of ice, into the water, it will erupt into a furious boil like
that in the photograph (they show a beaker exploding into a furious boil
that erupts out of the glassware), scattering water that could quickly scald
you."

   - Halliday, Resnick, Walker "Fundamentals of Physics" 1997

Microwaves use microwaves to heat the individual molecules, so it is
possible to impart more energy into those molecules than would normally take
to make them boil because a) the rapid energization b) the stagnant state of
the water. If you think about water on the stove there is a heat
differential that causes motion in the water that eventually yields a
"rolling boil" 

Thus, I would say that the event that transpired is possible.
-- 
Travis Lee
University of Minnesota: IT Honors Group

> From: Keith Hearn <khearn@Legato.COM>
> Reply-To: Keith Hearn <khearn@Legato.COM>
> Date:  Tue, 1 Feb 2000 13:33:54 -0500
> To: Multiple recipients of list <miata@realbig.com>
> Subject: Re: Physics question: [ABSOLUTELY NO NMC!]
> 
> 
> I'm skeptical, but not certain. I know it's possible to supercool
> water slightly below freezing without ice forming. Then with a
> slight disturbance it'll suddenly solidify. This is a well known
> phenominon, and is discussed in any decent chemistry text.
> 
> I'm not certain if it's possible to superheat it slightly above boiling.
> If it is possible, it would most likely only happen in an extremely
> clean, smooth container. Bubbles usually form at a "seed", either a
> spec of dust or a rough spot. With no seeds on which to form bubbles,
> the only vaporization would occur at the surface.
> 
> You can observe this "seed" phenominon by taking two clean glasses
> and leaving one out setting upright for a few days to get a little
> dust in it. Wash the other one, then pour a beer or soda into each. The
> dusty one will foam up a lot more than the clean one because there
> are more seeds on which the bubbles can form.
> 
> So if your cup was very clean and smooth, there might be no seeds for
> bubbles to form on. Then it might be possible for the water to be
> superheated. Pouring in something like instant coffee powder provides
> seeds, and it suddenly boils. Or maybe just disturbing it might be
> enough.
> 
> Having a teabag or wooden stirrer in the cup while heating would
> provide places for bubbles to form.
> 
> I don't know for sure that this superheating is possible, but I have
> heard stories of microwaved water suddenly foaming up when a
> powder is added to it. I haven't observed it myself, nor have I heard
> a reliable secondhand account of it. While supercooling is discussed
> in my chemistry textbook, there is no mention of superheating.
> 
> So there's a possible explaination. Dunno if it's real.
> 
> Keith Hearn
> '99 10AE "Sexy Sadie" the Sapphire Shark
> Milpitas, CA
> 
> In message <200002011723.MAA10940@marlin.exis.net>, Phredd writes:
>> 
>> Miataphyles: [Especially the physics majors amongst us]
>> 
>> I got the email below the other day warning me of dire injury
>> from exploding water when heated in a microwave oven. As I've been doing
>> just that for years, I just discounted it as just another Bullstuff Urban
>> Legend/E-scare thing. But, stuff happens.
>> 
>> The only way I can think that this could be possible is if the
>> atmospheric pressure were somehow dramatically lower outside the
>> microwave. But, even then, it would require that the appliance were gas
>> tight and, AFAIK, microwave ovens are not. And, even it it were, the
>> water would be likely to burst into boil the instant the door was opened
>> and the inside pressure lowered . . . rather than waiting for this
>> hapless boob to pick up the cup and stick his face over it, wouldn't it?
>> 
>> I wonder if this is the same guy who hooked up the JATO kit to
>> his Henry J.
>> 
>> Keep the Revs up!
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> Phredd  ~  Klassic Red '93A  ~  "Mr.Redd"  ~  Norfolk, Va. USA
>> 
>> God's Miata is Red!
>> 
>> 
>> 
>> 
>> ----------------the email below-------------------
>> 
>> 
>> Be careful when microwaving water.
>> 
>> I feel that the following is information that any one who uses a
>> microwave oven to heat water should be made aware of. About five days ago
>> my 26-year old son decided to have a cup of instant coffee. He took a cup
>> of water and put it in the microwave to heat it up (something that he had
>> done numerous times before). I am not sure how long he set the timer for
>> but he told me he wanted to bring the water to a boil. When the timer
>> shut the oven off, he removed the cup from the oven. As he looked into
>> the cup he noted that the water was not boiling but instantly the water
>> in the cup "blew up" into his face. The cup remained intact until he
>> threw it out of his hand but all the water had blown out into his face
>> due to the buildup of energy. His whole face is blistered and he has 1st
>> and 2nd degree burns to his face which may leave scarring. He also may
>> have lost partial sight in his left eye.
>> 
>> While at the hospital, the doctor who was attending to him stated that
>> this a fairly common occurrence and water (alone) should never be heated
>> in a microwave oven. If water is heated in this manner, something should
>> be placed in the cup to diffuse the energy such as a wooden stir stick,
>> tea bag, etc. It is however a much safer choice to boil the water in a
>> tea kettle. Please pass this information on to friends and family.
>> 
>> 
>> 
>> 
> 
> 
>