INTRODUCTION
Suppose
have an airtight and insulated walls in which water is in thermal equilibrium with its three phases, ice, water and steam. This system has the peculiarity that gives heat when the temperature increases, but the energy is consumed in the melting ice. That being said and not more than proof of an empirical fact, then will try to give a phenomenological explanation to the observed fact.
On planet earth, there are large areas where ice, water and water vapor coexist in nature. In Saturn's moon Titan is methane, which can found in these three phases, there are many compounds having triple point. For each of these compounds is possible to define a world where different phases are coexisting.
ICE
Ice is a crystalline structure where each molecule of water is confined in a given space on the network, this space is a well resulting from the existence of 3 bridges of hydrogen for every molecule of water. The molecule vibrates inside the well, like a marble that moves up and down inside a cup, becoming electrical potential energy into kinetic and vice versa in a row. For each temperature below the melting temperature there is a statistical distribution of the energies of the molecules, so that a few molecules have enough energy to leave your well creating a vacant and wandering around the net a short time before fall back. As the temperature increases the number of vacancies increases, we could accept that as the temperature increases the vacancy increase until a time when the original crystal structure has disappeared. This suggests that the phase change would actually result in a more or less wide range of temperatures and not a fixed, making what is actually happening is contrary to common sense. However we see that explained.
PHASES BETWEEN SURFACES
For simplicity suppose that the ice is subject to cables on the floor of the container so that there is no looming ice the surface of the water. In this configuration there are two surfaces, which separates the gas and liquid separating liquid from solid. Among these areas there is a transfer of particles leaving a stage to enter the next.
ICE-WATER SURFACE IN THE TRIPLE POINT
At the triple point due to the statistical distribution of energies of molecules, from ice surface are continuously emitting molecules into the liquid. These molecules have emerged in the solid has a very low average speed as they have had to overcome the pull of the well, ie, molecules that emerge from the ice are colder than the molecules that compose into liquid and tend to lower the temperature of the liquid. On the other hand, when these molecules were found inside the ice had great speed to escape both ice cold.
Also among the molecules near the surface of the ice there will be some who have a very low speed, so that in passing by a well can be dispelled some of the energy being confined. How are you were the coldest molecules of the liquid in the process the liquid is heated, while the ice is heated because the molecule has absorbed more energy than any that made up the ice.
As the temperature of the system grows, there will be a greater flow of molecules leaving the ice per unit area, and there will be a lower flow rate of liquid molecules to leave to join the solid. In general, both phases can not coexist except at a certain temperature where the flows are balanced.
ADDING HEAT TO TRIPLE POINT SYSTEM
Imagine
heat by providing some means has been achieved hot water temperature to 2 º C while the temperature of the ice is left constant. Now the flow of water molecules that go into the ice is lower, while the flow of molecules leaving the ice is still the same, the uncompensated flow cooled the liquid until it reaches the temperature compensation ie 0 º C or until the end of the ice.
WHERE HEAT PRESS HAS IDO
Although at the beginning and end of process temperatures are the same, the existing ice has decreased. A temperature thermal motion contributes to the same extent the molecule is inside a well outside of it. A free molecule with the same thermal motion contained a molecule has more energy because it contains the photons necessary to have escaped from the well. By reducing the number of molecules confined temperature remaining constant, the energy of the system increases.
CONCLUSIONS
The phase change is a consequence of the statistical link flows through the surface of phase change with the thermodynamic variables.
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