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1/25/2018 7:38:29 AM
Posted: 4/29/2002 6:34:22 AM EST
> > >I was very glad to get this email from a friend, > > >because I have been guilty of heating water in a > > >microwave many times. You'll be glad you read it. I > > >also suggest passing it along to friends and family. > > > > > >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 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 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 our science teacher 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. 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. > > > > > >Please pass this on to everyone you know, it could > > >save a lot of pain and suffering. > > > >
Link Posted: 4/29/2002 6:39:54 AM EST
Link Posted: 4/29/2002 6:40:04 AM EST
True. Microwaves can superheat water, and any disruption (wooden stick, stirrer, your lips) will cause it to (for all intents and purposes) explode violently causing serious burns. the_reject
Link Posted: 4/29/2002 6:43:24 AM EST
I just heat it till its hot. I've never tried to boil water in the microwave, always us a pan on the stove. Good to know this is what would happen if I did. Bill3508
Link Posted: 4/29/2002 6:43:30 AM EST
It's true.
Link Posted: 4/29/2002 6:49:04 AM EST
Link Posted: 4/29/2002 6:52:02 AM EST
Ban microwaves. For the children.
Link Posted: 4/29/2002 6:57:53 AM EST
Link Posted: 4/29/2002 9:25:52 AM EST
Link Posted: 4/29/2002 9:36:52 AM EST
Originally Posted By Norm_G: Bullsh!t.
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Good point! Can bullsh!t be superheated in the microwave? I don't think so. I'd say the grass and other undigested bits of feces would trigger a boiling event before it reached the superheated state. But thanks anyway for the input [b]Norm_G[/b].
Link Posted: 4/29/2002 10:10:09 AM EST
Originally Posted By Renamed: [url]http://rabi.phys.virginia.edu/HTW/[/url]
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From that source:
When I heat a cup of water in my microwave oven to 200 degrees, then put a spoonful of instant coffee in the hot water, it foams up. Hot water from a coffee maker does not do this. Why does water heated in a microwave oven do this? -- WAH, Library, Pennsylvania The microwave oven is superheating the water to a temperature slightly above its boiling temperature. It can do this because it doesn't help water boil the way a normal coffee maker does. For water to boil, two things must occur. First, the water must reach or exceed its boiling temperature--the temperature at which a bubble of pure steam inside the water becomes sturdy enough to avoid being crushed by atmospheric pressure. Second, bubbles of pure steam must begin to nucleate inside the water. It's the latter requirement that's not being met in the water you're heating with the microwave. Steam bubbles rarely form of their own accord unless the water is far above its boiling temperature. That's because a pure nucleation event requires several water molecules to break free of their neighbors simultaneously to form a tiny steam bubble and that's very unlikely at water's boiling temperature. Instead, most steam bubbles form either at hot spots, or at impurities or imperfections--scratches in a metal pot, the edge of a sugar crystal, a piece of floating debris. When you heat clean water in a glass container using a microwave oven, there are no hot spots and almost no impurities or imperfections that would assist boiling. As a result, the water has trouble boiling. But as soon as you add a powder to the superheated water, you trigger the formation of steam bubbles and the liquid boils madly.
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I have witnessed this myself - it's a real phenomenon. Pay attention!
Link Posted: 4/29/2002 10:12:32 AM EST
You're welcome. This reminds me of "spontaneous human combustion". Or maybe brain cancer from cell phones. Maybe this thread should have been titled "I boiled my face with superheated water".
Link Posted: 4/29/2002 10:49:13 AM EST
Superheating is likely only when the water and its container are very, very clean. Fortunately my tap water is so full of crud it won't superheat.
Link Posted: 4/29/2002 10:53:39 AM EST
Norm_G: Try it. Get a very clean measuring cup, fill it with bottled water, and nuke it until it boils. Turn off the microwave, take out the cup, and dump in, say, instant coffee. After you stop swearing, treat your burns. Microwave ovens CAN superheat water. It's a REAL phenomenon. I've burned myself making Cup-a-soup. I know.
Link Posted: 4/29/2002 10:53:58 AM EST
Its occuring because the water is a super-critical fluid, an unstable state and will transition from liquid to gas in a spectacular manner when given the first chance in order to be in the lowest energy state possible. Entropy is fun, microwaves are even more fun. Kharn
Link Posted: 4/29/2002 10:58:34 AM EST
Add the microwave to the "Things that are fun to shoot at thread" [:D]
Link Posted: 4/29/2002 11:01:26 AM EST
It'll never happen in mine, I have a post ban microwave.
Link Posted: 4/29/2002 11:07:17 AM EST
Norm_G, rare but true. [url]http://www.snopes2.com/science/microwav.htm[/url]
Link Posted: 4/29/2002 11:15:46 AM EST
put a light bulb in the microwave..enjoy the light show!! try it! have fun! i'm not a professional so i did this in someone else's home.
Link Posted: 4/29/2002 11:51:39 AM EST
Originally Posted By redray: put a light bulb in the microwave..enjoy the light show!! try it! have fun! i'm not a professional so i did this in someone else's home.
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cds are funner
Link Posted: 4/29/2002 12:01:29 PM EST
Sounds like fun. I'll have to try this some time...
Link Posted: 4/29/2002 12:15:59 PM EST
This is fact. I've seen it many times. It happens every time I make tea in a glass mug. No bubbles, but as soon as I start pooring in my teaspoon of sugar, boom! And depending how long I left the mug in the microwave, it can be downright explosive. You just have to be carefull.
Link Posted: 4/29/2002 12:32:27 PM EST
SSShhh... If the BATF sees this thread, they'll classify Water as a Destructive Device. Then we'll all have to get tax stamps for the posession of it.
Link Posted: 4/29/2002 12:53:12 PM EST
Norm says it cannot happen so that must be the case. Actually, phase transistion temperatures are NOT hard and fast. Liquid water can be heated above its boiling point without boiling at atmospheric pressure. The microwave does this quite eaily as it heats very uniformly when the object being heated can circulate. Water on the stove cannot be heated evenly as the finite temperature difference between the bottom of the container and the water insures nucleation at the boiling point. Likewise, water can exist as a liquid in sub freezing conditions.
Link Posted: 4/29/2002 1:30:44 PM EST
Why do I fear an outbreak of post titled "I just blistered my face boiling water"? [:)]
Link Posted: 4/29/2002 1:46:36 PM EST
I haven't seen this sort of thing happen when heating water, but I have seen it happen when cooling water. I did part-time work for a local college about 15 years ago, and they had a freezer setup with a very stable sand filled platform they used to make (well, attempt to make, they didn't turn-out very well) holograms. The object and laser had to be on extremely stable surfaces or the hologram would be ruined. They also seemed to work better when cold. One of the students showed me how you could leave distilled water in a beaker on the sand, and it wouldn't freeze until someone opened the door to the freezer. When you did so, the beaker shattered from the water suddenly turning into ice and expanding. We were fascinated by it and ruined a lot of good glassware investigating this phenomenon[:(].z
Link Posted: 4/29/2002 1:47:32 PM EST
Link Posted: 4/29/2002 3:39:24 PM EST
Freakin' morons, of course its true. Learn how to use a Microwave. You are supposed to put a chopstick in the cup first so bubbles will develope and boil normally. GG
Link Posted: 4/29/2002 3:45:22 PM EST
Link Posted: 4/29/2002 4:05:00 PM EST
From "How Things Work": In general, leaving a spoon in a cup of coffee or bowl of oatmeal isn't going to cause any trouble at all. I do it all the time. In fact, having a metal spoon in the liquid may reduce the likelihood of superheating the liquid, a dangerous phenomenon that occurs frequently in microwave cooking. Superheated liquids boil violently when you disturb them and can cause serious injuries as a result. Isn't a metal anything in a microwavea no-no? Scott
Link Posted: 4/29/2002 4:13:04 PM EST
[Last Edit: 4/29/2002 4:14:00 PM EST by LotBoy]
Pure Pooh [img]http://www.stopstart.fsnet.co.uk/smilie/dung.gif[/img]
Link Posted: 4/29/2002 7:02:25 PM EST
[Last Edit: 4/29/2002 7:03:11 PM EST by prk]
Originally Posted By LotBoy: Pure Pooh [img]http://www.stopstart.fsnet.co.uk/smilie/dung.gif[/img]
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Unsupported conjecture by LotBoy
Link Posted: 4/29/2002 7:09:50 PM EST
I thought that a carousel microwave would be less likely to superheat the water because of the movement of the container as it was being heated. But I got some to superheat the other day. Tap water in a measuring cup. I used to have a book mark of a webpage that showed you all the cool things you could do with an old microwave.
Link Posted: 4/29/2002 7:11:30 PM EST
Here is one of the pages: [url]http://www.sci.tamucc.edu/~pmichaud/grape/[/url]
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