Heating Water in the Microwave-Serious Stuff
> >
> >
> > 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. Then
instantly
> >the water in the cup "blew up" into his face.
> >
> > The cup remained intact until he threw it out of h is 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 may also 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 such as
a
> >wooden stir stick or a tea bag should be placed in the cup to diffuse the
> >energy.
> >
> > Here is what a science professor has 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 any time water is
> >
> > heated and will particularly occur if the vessel that the water is
> >heated in is new. 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. Then, what 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."
> >
> > Check out the site below to confirm the truth in this.
> >
> > http://www.phys.unsw.edu.au/~jw/superheating.html
>
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