why dave bergman is neat

Microwaving Water!

(I did not know this, did you?)

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.

Thank You Very Much.

# posted by Eric : 5:10 PM