Did You Know?....

Vlad D Impeller

Commander
Joined
Mar 30, 2005
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2,644
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).

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.
 

scipper77

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Sep 30, 2008
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Re: Did You Know?....

I'm short on time so this will be a short response.
What I understand is that water molecules are polarized and in a microwave they align themselves all in the same direction. If the cup is smooth and the water stagnant then you can superheat the water as the Magnitron in the microwave alligns all of the molecules in the same direction. When you drop your tea bag in the water.... Bang!

This is from memory and I didn't take the time to look it up and verify, buy I know someone else here will.
 

v1_0

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Joined
Aug 27, 2007
Messages
575
Re: Did You Know?....

I'm short on time so this will be a short response.
What I understand is that water molecules are polarized and in a microwave they align themselves all in the same direction. If the cup is smooth and the water stagnant then you can superheat the water as the Magnitron in the microwave alligns all of the molecules in the same direction. When you drop your tea bag in the water.... Bang!

This is from memory and I didn't take the time to look it up and verify, buy I know someone else here will.

Molecular Allignment? ? ? Where did you hear this?
 

david_r

Lieutenant Junior Grade
Joined
Aug 11, 2008
Messages
1,118
Re: Did You Know?....

its in your microwave manual!!!!

please dont tell me everyone on here just plugs it in when they get a new microwave?!...........these products change with time and technology.........what is happening is people are becoming too comfortable with electronics.......i read through everything when i buy it.

thats why manufacturers put manuals inside these products....................when you buy a new car you go through the manual to check it out right?!...........even though you know how to drive a car!

i hope the guy is ok and ends up without scars.

another pet peeve of mine is warranties............my wife just throws all the paperwork in the trash :eek:...............every time i have to dig through the trash to fill out the warranty papers she says "im sorry i didnt know you wanted those" then i can see that smirk :eek:.....yeah i think she does it on purpose too....funny thing is the stove she got for christmas last year----the clock has stopped working....no big deal other than the fact i gave $550 for it last year.......im in the process of filing the paperwork as we speak.
 

v1_0

Chief Petty Officer
Joined
Aug 27, 2007
Messages
575
Re: Did You Know?....

I've heard about this before, I think there's even a clip on utube about it.

At any rate, the simple solution is to put a non-metal (ie: plastic, wood) spoon/stirrer in the cup when you put it into the microwave to heat. The spoon creates a pathway for the boiling to happen, so it never gets into the superheated condition.
 

lowkee

Lieutenant Commander
Joined
Dec 13, 2008
Messages
1,890
Re: Did You Know?....

Wierd, I always thought superheating was caused by surface tension and and an object had to be breaking the surface in order to prevent it.

Next time my wife tells me to throw out my old jeans, I'll be sure to tell her "Wearing new clothes increases the chance I'll get superheated, and blow up in your face!" :)
 

scipper77

Commander
Joined
Sep 30, 2008
Messages
2,106
Re: Did You Know?....

Molecular Allignment? ? ? Where did you hear this?

My mistake. The explination I gave was the one for the question
"Why does water expand when it freezes?"
A: Molecular Geometry and Polarity

Water expands when it freezes due to molecular geometry and the fact that it is a very polar molecule. The water molecule is shaped like an upside-down "v". Due to this shape, when water freezes it make a hexagonal shape such that the slightly negatively charge oxygen atoms are aligned with the slightly positively charge hydrogen atoms -- this is the most stable configuration. (Less polar molecules do not configure themselves in this way because there is less of a reduction in energy if the molecule is not as polar) This orientation leaves space in the middle of the frozen water molecules. That is why water expands when it freezes.

I knew I should have taken the time to check my facts but I was in a rush when I originally replied, as I indicated.
 

Beefer

Lieutenant Commander
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Aug 4, 2008
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1,737
Re: Did You Know?....

First time I heard of this was when it happened to me. I was heating up a cup of coffee, took it out of the microwave, and when I put a spoon of sugar in, BAM! It was the freakiest thing. Luckily I wasn't holding the cup or had my face above it, and only got a drop or two on my hand (man did that hurt!). Nobody I told about it had ever heard of such an occurrence, but a few years later, there was a snippit on the news about it. I have since retired from reheating coffee. Tastes better fresh anyways.
 
Joined
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Re: Did You Know?....

I saw where pure distilled water will superheat quicker in a microwave and then gush out when you add something to it. A little trick but one you must be very careful with is to heat a wet towel for a short time and you get a quick heating pad for muscle cramps. At one time I would get severe cramps sometimes in both upper legs at the same time with intense pain. A quick hot towel would quickly make them stop.
 

ninjashoes

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Jan 19, 2008
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Re: Did You Know?....

I saw where pure distilled water will superheat quicker in a microwave and then gush out when you add something to it. A little trick but one you must be very careful with is to heat a wet towel for a short time and you get a quick heating pad for muscle cramps. At one time I would get severe cramps sometimes in both upper legs at the same time with intense pain. A quick hot towel would quickly make them stop.

I heard of people doing the opposite and sitting in tubs of ice.
 

stevenw00

Petty Officer 3rd Class
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May 25, 2008
Messages
91
Re: Did You Know?....

Most tap water will not super heat because it has impurities in it. Distilled water is capable of doing it, but it still has to be in a smooth cup, the microwave can't vibrate enough to break the surface tension, etc.

By the way, you can put a metal spoon in the microwave w/o doing any damage. The only time you'll see something spark in the microwave is if you have two edges of metal near each other (like crinkled aluminum foil, prongs on a fork, etc.) Since a spoon doesn't have any edges for electrons to jump from/to, you won't have any problems other than your spoon getting really friggin' hot, really fast. (which is why I don't recommend it)


Mythbusters also did a good show on super heating water, that is worth a watch if you can find it.
 
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