Re: Water Boil Water

[Chuck Britton <britton@odie.ncssm.edu>]

> I have a question for you guys out there. This question was raised by
                           ^^^^
                           (I suppose we ARE excluding grandmothers!)

> my Head of Department (Science) who in turn was asked by a student
> who took part in the Australian Science Competition a year ago.
>
> We know water boils at 100 degress C.
> Suppose I have a glass bottle half-filled with water. I place this bottle
> (with no capping) into a pot of water that covers two-thirds of the
> bottle. Now I
> boil this pot of water (also not covered). Will the bottle of water boil?
>
> I thought it would. I did not try it out yet. But my HOD was actually
> trying out
> the experiment in his home when his grandmother came in to the kitchen, saw
> what he was doing, gave him a thorough scolding, and told him that the
> bottle of water will never boil in this way.
>
> My question is: Is she correct? If she is, what's the theory behind it?
>
> Thanks.
>
> Steven.

Grandmothers are ALWAYS correct, haven't you learned that lesson yet!

It's all a matter of just exactly what meaning you attach to the word BOILING.
If you mean, 'bubbles forming on the bottom and rising to the top' than no,
it WON'T 'boil'.

If you mean having it reach a temperature at which the vapor pressure of
the liquid equals the ambiant air pressure, thereby resulting is 'rapid'
phase change from liquid to vapor, then yes it WILL do this.

Aren't words, and their various meanings a WONDERFUL thing!

As we cool liquid Helium-4 by pumping to lower and lower pressures (and
temperatures) it bubbles as it boils until it reaches the lambda
transition. At this point the superfluid component has such totally
humongous thermal transport ability that bubbles don't have a chance to
form and the 'heat' travels at the speed of 'sound' to the surface.

Boiling water requires a substantial thermal gradient in order for a
'rolling' boil  to occur.

It's no accident that stressed		Chuck Britton
spelled backwards is desserts.		britton@odie.ncssm.edu