[oregon-l] Microwaving Water!

[John A. Fleming]

Something we all need to know.

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 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 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).

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

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