Microwaving Water

A 26-year old man decided to have a cup of 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 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 suddenly 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 flown out into his face due to
the build up 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 is 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, (nothing
metal). It is however a much safer choice to boil the water in a tea kettle.

General Electric's Response:

"Thanks for contacting us, I will be happy to assist you. The e-mail
that you received is correct. Microwaved water and other liquids do not
always bubble when they reach the boiling point. They can actually get
superheated and not bubble at all. The superheated liquid will bubble up
out of the cup when it is moved or when something like a spoon or tea
bag is put into it. To prevent this from happening and causing injury,
do not heat any liquid for more than two minutes per cup. After heating,
let the cup stand in the microwave for thirty seconds before moving it
or adding anything into it."

Here is what our local science teacher had to say on the matter: "Thanks
for the microwave warning. I have seen this happen before. It is caused
by a phenomenon known as super heating. It can occur anytime water is
heated and will particularly occur if the vessel that the water is
heated in is new, or when heating a small amount of water (less than
half a cup).

What happens is that the water heats faster than the vapor bubbles can
form. If the cup is very new then it is unlikely to have small surface
scratches inside it that provide a place for the bubbles to form. As the
bubbles cannot form and release some of the heat has built up, the
liquid does not boil, and the liquid continues to heat up well past its
boiling point.

What then usually happens is that the liquid is bumped or jarred, which
is just enough of a shock to cause the bubbles to rapidly form and expel
the hot liquid. The rapid formation of bubbles is also why a carbonated
beverage spews when opened after having been shaken."

If you pass this on you could very well save someone from a lot of pain
and suffering.

==========================================

I wonder if this will work with regular unleaded?

Fiery Pig

On Tue, 26 Jun 2007 18:28:50 GMT, "DirtySickPig@PigsLodge#1"
> wrote:

>Microwaving Water
>
>A 26-year old man decided to have a cup of 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 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 suddenly 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 flown out into his face due to
>the build up 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 is 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, (nothing
>metal). It is however a much safer choice to boil the water in a tea kettle.
>
>General Electric's Response:
>
>"Thanks for contacting us, I will be happy to assist you. The e-mail
>that you received is correct. Microwaved water and other liquids do not
>always bubble when they reach the boiling point. They can actually get
>superheated and not bubble at all. The superheated liquid will bubble up
>out of the cup when it is moved or when something like a spoon or tea
>bag is put into it. To prevent this from happening and causing injury,
>do not heat any liquid for more than two minutes per cup. After heating,
>let the cup stand in the microwave for thirty seconds before moving it
>or adding anything into it."
>
>Here is what our local science teacher had to say on the matter: "Thanks
>for the microwave warning. I have seen this happen before. It is caused
>by a phenomenon known as super heating. It can occur anytime water is
>heated and will particularly occur if the vessel that the water is
>heated in is new, or when heating a small amount of water (less than
>half a cup).
>
>What happens is that the water heats faster than the vapor bubbles can
>form. If the cup is very new then it is unlikely to have small surface
>scratches inside it that provide a place for the bubbles to form. As the
>bubbles cannot form and release some of the heat has built up, the
>liquid does not boil, and the liquid continues to heat up well past its
>boiling point.
>
>What then usually happens is that the liquid is bumped or jarred, which
>is just enough of a shock to cause the bubbles to rapidly form and expel
>the hot liquid. The rapid formation of bubbles is also why a carbonated
>beverage spews when opened after having been shaken."
>
>If you pass this on you could very well save someone from a lot of pain
>and suffering.
>
>==========================================
>
>I wonder if this will work with regular unleaded?
>
>Fiery Pig



http://www.snopes.com/science/microwave.asp

Roughrider50 wrote:
> On Tue, 26 Jun 2007 18:28:50 GMT, "DirtySickPig@PigsLodge#1"
> > wrote:
>
>> Microwaving Water
>>
>> A 26-year old man decided to have a cup of 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 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 suddenly 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 flown out into his face due to
>> the build up 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 is 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, (nothing
>> metal). It is however a much safer choice to boil the water in a tea kettle.
>>
>> General Electric's Response:
>>
>> "Thanks for contacting us, I will be happy to assist you. The e-mail
>> that you received is correct. Microwaved water and other liquids do not
>> always bubble when they reach the boiling point. They can actually get
>> superheated and not bubble at all. The superheated liquid will bubble up
>> out of the cup when it is moved or when something like a spoon or tea
>> bag is put into it. To prevent this from happening and causing injury,
>> do not heat any liquid for more than two minutes per cup. After heating,
>> let the cup stand in the microwave for thirty seconds before moving it
>> or adding anything into it."
>>
>> Here is what our local science teacher had to say on the matter: "Thanks
>> for the microwave warning. I have seen this happen before. It is caused
>> by a phenomenon known as super heating. It can occur anytime water is
>> heated and will particularly occur if the vessel that the water is
>> heated in is new, or when heating a small amount of water (less than
>> half a cup).
>>
>> What happens is that the water heats faster than the vapor bubbles can
>> form. If the cup is very new then it is unlikely to have small surface
>> scratches inside it that provide a place for the bubbles to form. As the
>> bubbles cannot form and release some of the heat has built up, the
>> liquid does not boil, and the liquid continues to heat up well past its
>> boiling point.
>>
>> What then usually happens is that the liquid is bumped or jarred, which
>> is just enough of a shock to cause the bubbles to rapidly form and expel
>> the hot liquid. The rapid formation of bubbles is also why a carbonated
>> beverage spews when opened after having been shaken."
>>
>> If you pass this on you could very well save someone from a lot of pain
>> and suffering.
>> ==========================================
>> I wonder if this will work with regular unleaded?
>> Fiery Pig
>
> http://www.snopes.com/science/microwave.asp

That "Status: true, but rare" takes this out of urban legends! Hey,
Roughrider, thanks!

I now withdraw my "I wonder if this will work with regular unleaded?"
Don't try to replicate the described perfect conditions at home. Go to
a motel.

On Jul 3, 11:03?am, Dirty Sick Pig > wrote:

> That "Status: true, but rare" takes this out of urban legends! Hey,
> Roughrider, thanks!

The subject of superheated water tweaked my curiousity as a steam
plant engineer. But we usually talk about superheated *steam* in the
industry.

Water that is heated to a fraction of a degree above 212 degrees at
sea level air pressure of 14.7 PSI is superheated water all right,
it's actually *heat saturated* and cannot exist in the liquid state,
it has to intaneously change to a gaseous state, *flashing* into
steam.

Walking around a steam plant at night is a weird experience. Steam in
the pipes overhead cools down below the temperature at which it is a
gas and turns into water again.

Then the control room operator needs to send a lot of steam through
the pipes to some process that needs steam, that adds heat to the
water and the water heats up and flashes into steam again with a loud
BANG!

But nobody ever talked about bubbles forming in the water and somebody
getting a faceful of superheated scalding water, the steam was in the
pipes where it belonged.

>From a thermodynamic viewpoint, a British Thermal Unit is the amount
of heat required to raise the temperature of one pound of water one
degree Fahrenheit.

We're talking about a teacup full of water here, about 0.25 pounds,
and the water out of the tap is about 55 degrees. To bring the water
to boiling, we have to raise the temperature 212 minus 55 = 157
degrees.

157 X 0.25 pounds = 39.25 BTU's. That's still too much energy to be
putting into the water.

Why do microwave users want to pour so much excess energy into the
water that they are boiling? Why boil a cup of water to stir
a spoonful of instant coffee mix into it and then have to wait for the
water to cool down so they can drink their coffee without burning
their mouth?

Well, they aren't just heating the water, they have to heat the cup
too, and the specific heat of the cup's material is different from the
specific heat of water, which is 1.0.

To convert microwave wattage to BTU's, multiply times 0.0586.

My microwave puts out 900 watts on high, so it is pouring 900 X 0.0586
= 52.7 BTU's into the tea cup full of water in a minute.

The water absorbs heat because the molecules of water are polarized
and the alternating electromagnetic field of the microwaves sends the
molecules spinning and bumping into each other.

52.7 divided by 0.25 = 211 degrees, if the water was all that was
being heated, instead of the water *and* the cup.