Friday, January 12, 2007

and yet more from the Sober Husband

It is one of the Occasional Features of this blog that the readers' questions are put to the Sober Husband. Completely coincidentally the Drunken Housewife got very angry, in an unrelated matter, after soliciting questions, and consequently the Sober Husband has, in a conciliatory manner, been working extra hard to get those questions answered. Herewith Another Question Answered By The Sober Husband, this one going out to one of our delightful Texas correspondents, Texzmissy:

My question for the Sober Husband: True or false: You can microwave a cup of water and when you take it out of the microwave, if you are not careful, the water can more or less "explode" and you can get your face burnt with the presumably boiling water.

I say no, but my daughter insists that her science teacher says it's possible. Of course, it could be that the teacher said it was NOT possible, or only theoretically possible, and she wasn't listening, but I'd still like to know.


My first response is that it seems ironic when a science teacher is cited as an authority, especially on a subject that is so easy to explore experimentally. If I were the teacher, I would say: Try and see.

Anyway, I've tried. I have certainly been able to generate fairly violent splatters from a mug of hot water.

The idea is that while boiling requires high temperatures, it also requires sites for "nucleation" of the gas phase, like particles suspended in the water, or rough structures on the surface of the container. If the water is clean and the container is large enough, I think the water may well become "superheated" in the center (hotter than its boiling point) while still not converting into gas. Then when some nucleating material is introduced, like a teabag, there can be lots of thermal energy ready to generate a lot of steam in a short time.

I suspect a lot depends on the oven, the container, the heating time, and the stillness of the water. First, put the container in the oven, wait five minutes for the water to become absolutely calm, and then see how long you have to heat it before it starts boiling. Then, put the exact same amount and temperature of water in the same container in the exact same part of the oven, let it become calm, and heat it for ten seconds less. Leave it in the oven, but drop in a spoonful of sugar.

Let us know what happens.

Please perform this experiment at your own risk. The Drunken Housewife is not responsible for any injuries or damages sustained in the pursuit of science.

5 comments:

hughman said...

i can do science too, you know.

question - if you eat a mentos and drink a soda and then jump up and down, is it true your stomach will explode?

not that i eat mentos. ew.

Anonymous said...

I wish I could tell you where, but I saw an experiment on this. It is, apparently, dangerous. I have seen Alton Brown on food network say that you need to put a wooden skewer or something in to break the water seal to keep this from happening. Who knows.....may be a scientific anomoly.

Just found your blog and am enjoying it. Check mine out if you wish. wineplease!

Anonymous said...

Thanks Rinny!

I KNEW I had seen that someplace, it was on Good Eats. Ever since that episode I use a chop stick in the container when heating water in the mic.

Anonymous said...

I'd like to second the explanation offered by the Sober Husband.

The phenomenon in which a superheated liquid reacts violently to a disturbance is sometimes called bumping.

In chemistry labs, some experiments employ the use of boiling chips to provide nucleation sites as a preventative measure.

--
2amsomewhere
BS & MS in Chemical Engineering
Survivor of Organic Chemistry

texzmissy said...

Thank you, Sober Husband. That is so much a better answer than my original one, which was, "Are you crazy?"

But then, I did do-nut runs for my physics teacher in high school. The only physics questions I have now are basically, "How did that wreck happen?" If I had known how often I would ask that, I would have paid better attention in class.

Also, I asked my daughter today how the whole question ever came up in her class, and she said it was because one kid put microwave popcorn and cocoa in the microwave at the same time, and after leaning over and getting his face burnt slightly with the cocoa, he then opened up the popcorn and singed his face again with the steam.

So you can see why the teacher's first response wasn't "Try it and see" because there are not many signs of intelligent life on Planet Middle School. At least, not in my daughter's class.

Thanks again. I'm going to try and think of another question before Sober Husband tires of this game.