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: [Phys-L] phase change



T is constant at P constant, but not total area

for exampley if some liquid is boilling, and you increase the heat at the
bottom, and local temperature "wants" to go high,
a bubble will be formed.

So T is constant.


2016-02-24 18:58 GMT-03:00 Carl Mungan <mungan@usna.edu>:

Argh, still one typo. Okay this is it.

1. Why is there a definite sublimation temperature T?


The idea only works at constant /pressure/, with the solid
nearly in equilibrium with its vapor.

With that added requirement, the explanation is pretty simple.
All physics is /locall/. Look at what is going on locally at
the surface. The surface doesn't know how much solid is
behind it or how much vapor is in front of it; all it knows
is the local temperature, pressure, density, et cetera.
None of that changes as the reaction progresses.


I interpret this idea to mean: Since the gas and solid are in thermal
contact (at the surface) and in (at least quasi) equilibrium, they have to
be at the same temperature. Further the surface doesn’t know how big
overall it is, so there can only be one local sublimation temperature (at
any given pressure).

Fair enough, I can’t object to that. I now revise my question 1 to:

1. Do the particles in the gas and in the solid have the same (a) average
kinetic energy? (b) average total energy?

With regards to 1(a), I still wonder if folks think the animation on the
following page is basically okay or not:


http://zonalandeducation.com/mstm/physics/mechanics/energy/heatAndTemperature/changesOfPhase/changeOfState.html
<
http://zonalandeducation.com/mstm/physics/mechanics/energy/heatAndTemperature/changesOfPhase/changeOfState.html


-----
Carl E Mungan, Assoc Prof of Physics 410-293-6680 (O) -3729 (F)
Naval Academy Stop 9b, 572C Holloway Rd, Annapolis MD 21402-1363
mailto:mungan@usna.edu <mailto:mungan@usna.edu>
http://usna.edu/Users/physics/mungan/ <
http://usna.edu/Users/physics/mungan/>
_______________________________________________
Forum for Physics Educators
Phys-l@www.phys-l.org
http://www.phys-l.org/mailman/listinfo/phys-l




--
Diego Saravia
Diego.Saravia@gmail.com
NO FUNCIONA->dsa@unsa.edu.ar

====================================================================
"Disclaimer:" Haré lo que desee con los correos que reciba, quien no este
de acuerdo, que se abstenga de enviarme correo a mí o a las listas donde
este suscripto.
En particular NO VALE ningun "disclaimer" que indique que el correo enviado
es privado o sujeto a normas de empresas, gobiernos, u organizaciones de
cualquier tipo.
Con relación a los estados y sus leyes, analizare cualquier norma aplicable
en el territorio donde eventualmente actúe en el momento, escucho a
cualquiera que tenga algo que decir.
Con respecto en particular a los derechos de autor, salvo acuerdo previo,
gozaré plenamente de las 4 libertades con todo lo que reciba,
considerandolo, en cuanto a lo patrimonial,
como propio.
====================================================================