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Explosion in microwave

  1. Feb 28, 2004 #1

    Monique

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    Did any experience that before? I was in the lab, luckily, microwaving 100 ml of water in an *open, no lid* 500 ml erlenmeyer flask. All of a sudden there was this big *boom* in the microwave like an explosion, when I open it.. water is dripping from the sides and about 25 ml were missing I was like: wtf

    I actually experienced boiling delay with microwaves before, but not quite this spectacular - or dangerous -
     
  2. jcsd
  3. Feb 28, 2004 #2

    LURCH

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    That kind of thing can result if you sue very clean water in a very clean container with very smooth sides. There are not sufficient points of veriation on which gass bubbles can form. So the water passes the boiling point by quite a bit before it can actually start to boil. Once a single bubble forms and creates a disturbance, the rest can flash transition to a gasseous state, expanding violently.

    For this reason, many microwave ovens come with a warning not to boit water ni them. People have been injured by water that passed the boiling point but did not boil. A victim will continue heating the water, observing that is not yet boiling. Then, in an attempt to check the temp, they will remove the cup from the oven and look directly into it. The movement sets off the the transition process, and the cup acts like a guyser, spraying superheated water into the face.

    It's been mentioned in the Forums before, but I thought it worth repeating to anyone who didn't catch it the other times. Important safety tip!
     
  4. Feb 28, 2004 #3

    Evo

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    Thanks Lurch!!
     
  5. Feb 28, 2004 #4

    kat

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    Ouch, really...thanks for the warning!
     
  6. Feb 28, 2004 #5
    great...now I fear my microwave.
     
  7. Feb 28, 2004 #6
    Think I'll stick with the toaster from now on.

    cookiemonster
     
  8. Feb 28, 2004 #7

    LURCH

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    Dude, DO NOT attempt to boil water in your toaster! Don't ask how I know, but it's a bad scene and you don't want to go there.
     
  9. Feb 28, 2004 #8
    Wouldn't it just be safer to take some wood, go outside, and build a fire? Or you could resort to a bunsen burner to do your cooking hehe.
     
  10. Feb 29, 2004 #9
    Good point.

    But you know I have to ask... How do you know?

    Edit: Ooh, looky me. I get a title. Don't I feel special.

    cookiemonster
     
    Last edited: Feb 29, 2004
  11. Feb 29, 2004 #10

    Monique

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    Yes, or know how long to microwave it.

    In the lab we always use the microwave to make agarose gels. Even though we add a powder that turns into a gel when heated, you still get a boiling delay. But since the liquid is very viscous, it doesn't really overboil. At this event I wanted to clean the flask, since some of the gel had cooled in it.

    The microwave is very clean now
     
  12. Feb 29, 2004 #11

    ShawnD

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    I've never had an explosion in my microwave but I have made huge fireballs in it . Put some rubbing alcohol in the microwave and nuke it for 15 seconds. Open the door use your light to ignite the vapours (wear leather gloves and a jacket).
    It's lots of fun.
     
  13. Feb 29, 2004 #12

    Monique

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    A classical example of: *don't try that at home*
     
  14. Feb 29, 2004 #13

    ShawnD

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    If it makes you feel any better, I was doing it outside.
    Microwaves are awesome.
     
  15. Feb 29, 2004 #14
    I've never actually microwaved water before, but I HAVE seen a video clip of it online. Just a small disturbance of the water would set the water boiling madly. I think there is a term for this called superboiling/superheating (can't remember which).

    Anyway, why use the microwave? There's always the good-old kettle...
     
  16. Feb 29, 2004 #15
    MythBusters?

    Monique,

    Have you ever seen the show "MythBusters" on the Discovery Channel? It's a great show about disproving common misconceptions about everything; like on this one episode tha I watched they were trying to discover any truth to the idea that if you drop a penny from the Empire State Building and it hits someone on the head, their head will explode and they'll die. They found out how tall the Empire State was exactly and crafted this tube to drop a penny down. They have this dummy that is exactly like a human in every physical way, and so they put one end of the tube on the dummy's head and dropped the penny into the other end, and, well... Let's just say that that particular "myth" is very much true. Yuck. Anyway, they often treat themselves to the pleasure of watching things melt, explode, and other such enjoyable things in one of their several reinforced microwaves. Your story reminded me of this as soon as I read it. You should try to see the show sometime. The hosts are complete psychopaths, but they're geniuses as well. Good show!
     
  17. Feb 29, 2004 #16
    I didn't know what to expect from this thread - the epoch of decoupling or a bursting potato?
     
  18. Feb 29, 2004 #17

    Evo

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    and don't microwave whole eggs still in their shell
     
  19. Feb 29, 2004 #18
    Does it have to be in a microwave for this to happen? I didn't see anything in Lurch's explanation that seemed specific to microwaves.
     
  20. Feb 29, 2004 #19
    I think it has to be in microwave.
    Microwave gives you uniform heating and temperature increase of complete water volume. If you use, for example, kettle and stove, you’ll have temperature gradient with hotter bottom and colder top – creating currents inside the kettle (no effect).
    + There’s question about pressure inside microwave oven (is it hermetically closed?).
     
  21. Feb 29, 2004 #20
    Good idea, and also dont put in aluminum foil unless you want to see pretty blue flashes of radiant energy.
     
  22. Feb 29, 2004 #21
    How much do a microwave oven's peaks and troughs of energy vary, and over what distance? While defrosting meat in a microwave, I try to move it around asymmetrically to avoid on average what might be a "cold" zone. Even a rotating platter tends to provide an thermally unbalanced center.

    -A hopeless physicist
     
  23. Feb 29, 2004 #22

    Monique

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    Inteference takes place in a microwave, so there ARE 'hot and cold' spots. The microwave I used had a rotating disk, it wasn't until the time was up and the disk stopped turning that the thing unleashed :P
     
  24. Mar 1, 2004 #23
    "Super Heating" only happens with distilled water. The imperfections with tap water allow the water to boil at normal temps. You only need to be cautious when boiling distilled water.
     
  25. Mar 2, 2004 #24

    Monique

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    When did you get that memo? I've never stuck a thermometer in a cup of water while microwaving it (can't be good :P), but superheating definately occurs with ordinary water. How else would you explain the phenomenon of delayed boiling?
     
  26. Mar 2, 2004 #25

    jimmy p

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    i thought microwaves only penetrated the first couple of milimetres of substances...how does that make them bery good at cooking?
     
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