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Re: How to explain this?



The same phenomenon can be observed, if less dramatically, when cooking
spaghetti... provided that you do it properly, and don't put the spaghetti
in until the water is boiling. Adding the spaghetti causes the
gently-boiling water to increase the boiling rate suddenly. The same thing
happens when you add the coarse salt to the water - my Italian students are
invariably familiar with this fact, and usually assume that it has
something to do with the dissolving of the salt, so it's interesting to
show that the same thing happens with non-soluble material.

Mark

At 11:15 18/02/03 -0500, Mark Lucas wrote:
This is an issue of superheating.

A google search on "superheated boiling" brought up the second link as:

http://newton.dep.anl.gov/askasci/chem00/chem00636.htm

They've got much better explanations than I could give.

Mark

On Tue, 18 Feb 2003, Ludwik Kowalski wrote:

> This morning I observed something unusual. A common cup
> filled up to about 80% with milk, and with about 1/2 spoon of
> dissolved coffee, was placed into a microwave oven. I opened
> the microwave door at the moment the milk started rising. Then
> I removed the cup and placed it on the table. I was glad that
> nothing was spilled. Nothing unusual so far.
>
> About ten seconds later I took a spoon (at room temperature)
> and immersed it into the cup. That resulted in a sudden rise of
> foam with milk and some of my coffee was spilled. How can this
> be explained? Why did placing a cold spoon into the hot coffee-
> milk produce a sudden boiling-like =93explosion?=94 I have never
> seen anything like this.
> Ludwik Kowalski
>

----------------------------------------------------------------------------
Mark Lucas email: lucasm@ohiou.edu
252D Clippinger Lab phone: (740)597-2984
Department of Physics and Astronomy fax: (740)593-0433
Ohio University
Athens, OH 45701

Mark Sylvester
UWCAd
Duino Trieste Italy