Boiling water in a microwave

[sjl52]

A little off the subject but another cool brain teaser, easy to demonstrate with the most basic lab gear:
If water can be made to boil by adding ice, can one make water freeze by boiling it?
I’m not telling but I’m sure some of you can.

[mikemurphy_155]

Ok so I had never heard of this before, until yesterday, when it happened to me. I’ll explain what happened and you guys can draw you’re own conclusions.

It’s was a cold Saturday afternoon in December. My girlfriend was nodding off on the sofa. I made us both a hot drink, me tea, her coffee. She has instant decaf coffee, the water is always boiled in a kettle, the mug is a decent sized mug (sorry I don’t know the size. She normally has 2 big spoons fills of coffee and 1/4 of the mug is filled with full fat milk, I normally put this into the cup before I put the water in so as I can stir the coffee in the milk so it isn’t as ‘bitty’ when the water goes in.
So the kettle boiled and I poured the water in and took it through to my girlfriend.

She slept for 4 hours, and a brain surgion doesn’t have to tell you, her coffee was now cold. so when she woke I put the mug in the microwave. One of my pet hates is stuff still being cold after being microwaved so i put it in for roughly 2 minutes.

When it pinged I opened the door, now this may throw a spanner in the works of a couple of theories but the floor of the microwave was covered in coffee. Suggesting the coffee had already boiled, which I believe goes against some people theory of nucleisation (but don’t get me wrong, I’m not here to debate, just tell my story). I put the coffee on the side and decided to give it a stir. When I put the tea spoon into the coffee, it violently erupted for half a second at most. It must have raised about an inch higher then the rim of the mug, and once it gave finished the mug was left with about 1/4 of the coffee still in it and the rest all over the counter and on the floor. It did burn my fingers which are still slightly sore today (it only happened yesterday though), and I am so glad that it didn’t happen as the coffee hit my girlfriends lips as she drank it.

So that’s my story, I’ve read a few accounts of this on various sites, all.of which have slightly different theories, including the nucleisation theory. Some people say its very rare and even rarer when there are substances in the water, such as instant coffee.
I’ve also found a demo on YouTube Don't make coffee with microwave - YouTube what you see in this video is pretty much what happened to me.

There’s a few people debating on this thread over the physics of it, I fear some arguments may be more opinion then solid facts, so does anyone actually have any links to a piece of valid academic research into this?

Is it a phenomenon? Does it require the most specific conditions? Or is it just something that happens when water is in a microwave too long?

[mikemurphy_155]

@Randy_B

From the “Warning” in Julie’s submission:
“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 stirrer stick / spoon, tea bag, etc.”

This part sounds like pseudoscience to me. A wooden stirrer stick can’t “diffuse the energy”, since wood is a pretty good thermal insulator, and microwaves won’t affect the solid part of the wood (only the water or oils inside). And you wouldn’t want to put a metal spoon in the cup for the same reason you don’t want to put any solid metal objects in the microwave: they absorb and/or reflect a lot of the microwaves, causing damage to your oven. “Energy diffusion” isn’t the desired effect, in any case. Count me as one of the supporters of bubble nucleation sites (or lack of them) as a cause of regular (or irregular) boiling.

For those of you who want to try to duplicate the volcanic explosion effect at home: a mechanical shock can cause a sudden release of gas or vapor in a bubbling or superheated liquid. For instance, you get maximum distance with a jet of Coke from a can if you (1) start with a warm can, (2) shake up the can, and (3) hit the bottom of the can against a solid surface immediately after opening the top. All the carbonation tries to come out of the liquid at the same time, driving some of the liquid quite far away from the can.

Come to think of it, that’s probably why I never have problems with superheated water. My microwave oven has a rotating table built into it which lurches around the whole time the microwaves are on, providing some stirring action and frequent (mild) mechanical shocks.

It happened to me yesterday, and my microwave also has a rotating table inside. Could this suggest the eruption could have been more violent had it not rotated?

[mikemurphy_155]

Continuing from my first post, I would like to highlight that the mug I used was just a regular mug, my opinion is that the inside would be a far from a perfect surface, given the amount of times a metal spoon would have been stirred around inside it, bashing against the side creating tiny cracks and crevices, especially given how long we’ve had the cup and how many cups of tea we have per day, or week.

Also I don’t see people talking about any other liquid but water, and most people seem to suggest it can only be don’t with pure water. Where as when it happened to me, the milk and coffee were in the cup while it was in the mircowave.

And as I mention in my last post my microwave rotates inside (although not fast enough to simulate stirring) could that have any effect?

Just throwing if out there for you.

[Irishman]

It most certainly can happen with other liquids. The key is that the liquids are homogenous - there are no particles suspended in the fluid which would serve as nucleation sites. Water is the most common liquid being heated.

[naita]

It’s unlikely it can be used to combat zombies though.

[mikemurphy_155]

@naita

It’s unlikely it can be used to combat zombies though.

Like it

[gamerunknown]

Well, the first thing to point out is that the “violent eruption” doesn’t need to be anything more than a centimeter over the rim to seriously injure someone handling it. Obviously caution must be used in handling all hot liquids, but in most cases they don’t suddenly evacuate their contents (apart from grease).

Also:

Well, how about the stories that are going around that the U.S. is NOT reponsible for destroying Hiroshima? The bombs dropped by the U.S. planes actually misfired. In fact, a proto-type microwave was being tested in Hirsohima that balmy day in 1945, and someone was boiling water which exploded, destroying the city.

I know this is true, because I read it online at the “Nazis for Free Speech” home page.

I was going to ask why they wouldn’t celebrate the nuclear annihilation of Japanese civilians until I realised Japan was an ally of the Nazis and instituted their own fairly xenophobic policies. Then I suppose they’re American nationalists, so they have to defend historical US foreign policy, so they want to portray America as the good guy as well as Hitler… Gosh, the cognitive backflips one has to perform in order to support oppressive regimes.

[davidm]

Wow, a super-heated electromagnetic Nazi Godzilla zombie! :eek: