Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: latent heat of evaporation



As far as i know no bubbles are formed when evaporation takes place
without boiling, for example at 90 C. Molecules
escape from a flat surface overcoming surface tension forces. That is
when, I suppose, the value of 540 cal/g is valid. This topic is new to
me. I do not know what to expect when bubbles are formed. Should L
become larger or should it become smaller than 540? Perhaps someone
will supply the answer based on thermodynamics. Or on laboratory data.
I am sure that the topic has been studied in the past.
Ludwik Kowalski


On Sunday, Sep 26, 2004, at 19:47 America/New_York, Herbert H Gottlieb
wrote:

I really do not fully understand your reply.
Don't bubbles always form below the surface???
Under what conditions would you expect the
bubbles to be formed elsewhere?

Herb :-)


On Sun, 26 Sep 2004 14:44:31 -0400 Ludwik Kowalski
<kowalskil@MAIL.MONTCLAIR.EDU> writes:
I suppose that latent heat of evaporation of water,
L=540 cal/gm, applies to evaporation from the
surface (to overcome attractive molecular forces).
What evidence can be found that L remains the
same during intensive boiling? I am watching a
heating resistor immersed in a beaker. In this
case most bubbles are formed below the
surface, near the heating coil.
Ludwik Kowalski




Herb Gottlieb from New York City
A friendly place to live and visit