The Rigged-Up Net

First it was aluminium foil… then people started throwing CD’s in them… and now, people are putting WATER in microwave ovens and causing mayhem!

Evidentally, this phenomenon known as “super heating” is well known — I dunno about you but I’ve never had a hot cup of water EXPLODE like this video shows.

Here’s the whole email message I got from Susan:

> My 26-year old son 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 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 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 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.
>
> General Electric’s response:
> Thanks for contacting us, Mr. Williams. 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.
>
> I hope this helps.
>
>
>
*************************************************************************

>
> 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 that 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.”
>
>
>(See attached file: superheating.mpeg)