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Author Topic:   Thermodynamics
Matt P
Member (Idle past 4805 days)
Posts: 106
From: Tampa FL
Joined: 03-18-2005


Message 13 of 27 (391256)
03-24-2007 3:39 AM
Reply to: Message 1 by Own3D
03-22-2007 5:54 PM


Thermodynamics of disequilibrium systems
Hi Own3D, welcome to EVC.
The evolution model postulates an increase in useable energy, information, and complexity of living organisms.
Let me first say that entropy seems to be an insurmountable problem in life/evolution/growth/etc., but that is due in large part to a major fatal flaw in your initial conditions. Whether or not you knew it, you assumed that your system started at or very near to thermodynamic equilibrium. Since there are several sources of energy available to life (chemical, solar, thermal, etc.), we can not assume that life is at thermodynamic equilibrium. Under such conditions that is synonymous with death.
It's a major fault in chemical education that thermodynamics only goes to the end of the 19th centrury. Work in thermodynamics in the 1950s and beyond has focused on the development of non-equilibrium thermodynamics. Ilya Prigogine was the leader of this field and received the Nobel prize in chemistry for his work (see Ilya Prigogine - Wikipedia ). Prigogine developed the mathematical basis for non-equilibrium thermodynamics. The math is tough but has been shown to be correct (see Belousov-Zhabotinsky reactions Belousov—Zhabotinsky reaction - Wikipedia).
Note that in order to understand thermodynamics, you have to understand some math and theoretical background. If you don't have the mathematical background, then you can't honestly hope to use thermodynamics to critique evolution.
Let's start with the first and second laws of thermodynamics expressed in chemical terms (modeled after Lunine 2004):
TdS = dE +pdV - SUMiXidNi
where T is the temperature, dS is the change in entropy, dE is the change of energy, p is the pressure, dV is the change in volume, X is the chemical potential of the species of interest in a chemical reaction, and dN is the change of number of atoms/moles of those species of interest.
We can determine the rate of change of entropy of the system if we keep the system energy and volume constant (a convenience which does not affect the generality of this relation). This becomes:
dS/dt = SUMiXidNi/dt
Now let's say we have a chemical reaction:
A B
In this reaction, let's say that "B" is more ordered than "A". The rates of the reaction, k1 and k2, denote the forward and the backward reaction rates, respectively.
The chemical potential for a species is proportional to the forward and the backward rates of reaction:
XA = CA * ln (k1 / k2)
XB = CB * ln (k2 / k1)
where C is just a constant that allows for proportionality.
The change in the number of moles of these species with respect to time is also proportional to the rates of reactions, that is:
dNAA/dt = k1 - k2
dNB/dt = k2 - k1
What happens now when we substitute these into the dS/dt relation?
dS/dt = C * {(k1 - k2) ln (k1/k2) + (k2 - k1) ln (k2/k1)}
If k1 is larger than k2, then the relation is positive, that is, dS/dt is positive (try it yourself!). If k2 is larger than k1, then the relation is still positive. This means that no matter which way the reaction procees, the change in entropy is positive! Even when B is being produced (order increases), the change in entropy also increases!
Non-equilibrium thermodynamics has hugely affected the field of biochemical thermodynamics, as it has influenced how we consider the chemical networks of what goes in life, in ecosystems, and elsewhere. It's not an easy subject, so there's still a lot more applications ready to figured out.
Hope this helps.

This message is a reply to:
 Message 1 by Own3D, posted 03-22-2007 5:54 PM Own3D has replied

Replies to this message:
 Message 14 by Own3D, posted 03-24-2007 5:01 AM Matt P has not replied

  
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