Re: superheated drink (was: How to explain this?)

[Bernard Cleyet <anngeorg@PACBELL.NET>]

"This tendency coupled with the poor thermal conductivity of most liquids
should tend to produce *pockets* of superheating."



This was the subject of a thread on another list.  I disputed this after
carefully depositing a few drops of india ink on the bottom of a glass
tumbler.  To successfully do this, I waited a long time before inserting
the drops (hypo./syringe) and did so very slowly.  I also did this in the
oven, as moving the beaker causes motion in the liquid.  Then I turned on
the oven.  I did this at least twice and always the ink flowed up and
quickly uniformly colored the liquid well before boiling.

Caveat:  low power oven with a fan to vary the nodes/antinodes position.

Where is the expert Bill Beaty?

bc  kitchen physicist (not always appreciated by GK)

p.s. my post on the ibrik may apply to this question



Larry Cartwright wrote:

> "John S. Denker" wrote:
> > To fully explain Ludwik's report, one has to imagine
> > that some of the liquid was superheated but some of
> > it wasn't.
>
> This tendency is suggested by experimental evidence.  Take a chunk (a US
> non-metric unit of mass) of frozen hamburger and nuke it in your
> microwave.  You will find that various portions of the burger are in
> different states, here thawed, there still frozen, and some portions
> cooked.
>
> This tendency coupled with the poor thermal conductivity of most liquids
> should tend to produce *pockets* of superheating.
>
> I believe this doesn't usually happen when liquids are heated on the
> stovetop because heating from the bottom sets up convection currents,
> which provide mixing that prevents hotspot pockets from forming.  An
> interesting (to me) gedanken:  what do you think would happen if were to
> heat a liquid on a stovetop with a flame *so intense* that it heats the
> water in the bottom of the pot to boiling before convection has an
> opportunity to set in?
>
> Best wishes,
>
> Larry
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Larry Cartwright     <exit60@cablespeed.com>
> Retired Physics Teacher
> Charlotte MI 48813 USA
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Lord, preserve us from the excesses of those
> who would do us harm; and preserve us from
> the excesses of those who would protect us.
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~