Spontaneous order from chaos

Discussion in 'Chemistry' started by Magical Realist, Sep 11, 2013.

  1. Magical Realist Valued Senior Member

    Two examples come to mind: crystal growth and autocatalytic reactions. How does this not violate the 2ND Law of Thermodynamics? Does removing energy from a system sometimes increase its order? For example the phase transition from water liquid to water ice? Is life itself an example of an autopoietic process?

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  3. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

    I don't think so. Each molecule bound in the crystal has lost energy. - Energy can lower entropy, but to restore the original or starting conditions will require more energy - it always does.

    Consider Salt and water: No crystals will form unless the solution is "super-saturated." To achieve that will require adding energy (evaporation heat) from some eternal source to the under saturated solution, whose entropy will increase, more than the decrease achieved as the some crystals form. If you drop a small salt crystal, a highly ordered arrangement of NaCl atoms, into less than saturated water they will separate and become more dis-ordered in accord with the 2Nd law.

    The second law applies to CLOSED systems. You can not just consider the formation of crystals from the super- saturated state - must include the entropy increase than made the super saturated state.
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  5. exchemist Valued Senior Member

    Ha, this is an old chestnut beloved of creationists, in the context of the increase in order implied by the formation of life from non-life (abiogenesis). I've actually used the example of crystal formation in arguments with them to show why they are mistaken. The point is that indeed that when water freezes, the entropy of the whole system i.e. including the surroundings, still increases, even though the entropy of the crystal is lower than that of the liquid from which it forms. When water freezes, the latent heat has to go somewhere and as it does it warms up that somewhere, increasing its entropy (dS = dQ/T) by more than the decrease in the freezing water.

    And when an organism grows, its metabolism provides ample increase of entropy of the surroundings to allows a local decrease in entropy as a new cell forms, without violation of the 2nd Law of TD.

    Autopoietic is not a term I'm familiar with but from looking it up it seems to mean self-maintaining. A crystal of ice doesn't fall into this category, so I wonder if there is a bit of disconnection between your last sentence and the rest of your post. I mean, life may be autopoietic, but what has this to do with the 2nd Law of TD?

    P.S. Tesla seems to have been talking out of his arse: not that unusual for him.
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  7. Aqueous Id flat Earth skeptic Valued Senior Member

    Magical Realist: This is technical concept that Creation Science likes to play games with. Billy T set it in caps to correct that error in thinking. You may ask "what is a closed system"? That's not a question I've yet heard a Creationist raise, but it's the one that their whole sense of nature turns on. By "closed" we mean we have a definitive boundary that encloses all of the elements of the system (usually devices in a mechanical system but this gets lost on Creationists too). The 2nd Law of Thermo ONLY applies to closed systems. That's their error. In a lab this fairly easy to recognize, because the bench where someone is making measurements is bounded by the test apparatus in some way. For example, if we're measuring the changes in heat during some test, the apparatus will normally be insulated to reduce the exchange of heat with the lab air, and thus the space inside the insulation is correctly identified as a closed system wherein the 2nd law applies. (There will be some loss through the insulation but when properly designed it's either negligible, or else there's a calibration method to account for it.)

    Contrast the scientific method for dealing with entropy against the religious method. In the Creationist view of science, God passes in and out of any closed system at will adding or subtracting heat or entropy as it pleases Him. In so doing God unconditionally violates the 2nd Law of thermo whereas the closed systems Bill T is referring to are compliant and thus "more pure than God".

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    In fact, a law of this kind is god. It simply can't be defeated. That's a tough row to hoe for all of the Creationists and anti-science crowd, but one that's entirely self-inflicted. They're just one or two science classes away from spotting the same error in other skeptics.

    Speaking of which, their eyes just glaze over. It's like talking to the wall.

    And isn't it true that the way a substance crystallizes is just due to the intrinsic properties of its constituent molecules? They are going to fall to their lowest energy state. They may look ordered, but that's entirely trivial. Thermo is inquiring into their energy states, not their apparent order, whereas information theory is looking at their order as if no other laws are in effect. There seems to be a general misconception about this among folks who raise it.

    Magical Realist: Consider this - take two sets of numbered billiard balls. One set is made from magnetized material such that when they are racked up, all up the numbers appear face-up. Once out of a zillion time the normal balls will also rack up in perfect order. Obviously neither system is violating the 2nd law of thermo. One is just pre-conditioned by its intrinsic properties to line up. Molecules can be of either kind. Creationists are complaining that the first kind represents all the order in nature, but it's simply naive to think that way (and that's putting it mildly). There are the second kind, too. Therein lies the rub.

    Somehow he has achieved folk status among skeptics, cynics and cranks. They miss the fact that he tended to be full of bull. This is another group (or possibly they are really undercover Creation Science folks) that has missed the boat on the meaning of closed systems as well as the chemistry of crystallization.
  8. exchemist Valued Senior Member

    Re crystallisation, I'm not sure it is entirely trivial that freezing solids increase their order while melting ones decrease theirs.

    It seems to me that the thermodynamic way of looking at things is quite subtle, involving a constant tension between, on the one hand, the tendency for systems to drop to their lowest energy state, and on the other, the probability of any given state, relative to the others the system could occupy. The amount of energy bubbling around determines what balance point is reached between these two competing influences.

    There are famous examples of endothermic dissolving of crystals, for example NH₄NO₃, which can only be explained by the probability influence winning, i.e. there are so many more states the molecules can explore once they dissolve that they do so, even though they have to gain energy to do it. It seems to me this is fairly counterintuitive until one applies the ideas of statistical thermodynamics.

    Re Tesla, he does indeed seem to be disproportionately championed by, er, eccentrics.
  9. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

    That is true for the net effect as the water cools but it is more complex as two different processes are taking place. New "hydrating" bonds are forming and releasing energy that happens to be less than the energy required to break the HN4NO3 bonds* I.e. the net energy required to break the bonds in the NH4NO3 molecule come from the water.

    A more difficult to understand process is the expansion of He or H2 into a vacuum in a well insulated container. There is no work done expanding into a vacuum and no heat transfer. Thus the enthalpy is unchanged, but the expanded gas is HOTTER (average kinetic enter per molecule has increased and number of molecules is unchanged.) than the original denser gas. This is very counter intuitive as humans only have experience with gases cooling as they expand or are "throttled." How can a process which makes greater disorder, increases entropy, also RELEASE heat? Usually processes that naturally occur and release thermal energy, typically do so by putting the reactants into more tightly bound compounds. Again, no work is done expanding into vacuum, no heat is absorbed from the environment, and no new compounds more tightly bound are formed.
    Any one want to explain this heating with expansion of He to me?

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    The JT coefficient is negative only for H2 & He at "room temperature."

    Following was written to explain how "add water" cold packs work:
    I happen to think the process is more complex still as water is not just H2O molecules. It is, especially at lower temperatures, short chains of n H2O molecules as the H2O molecule is intrinsically polarized. I.e. both Hydrogen are positively charged and on only one side of the negatively charged O molecule, with 105 degrees of angular separation between them. I.e. H2O in any physical state is really partially a polymer of this monomer: ++(H2O)-- but the electron transfer is not complete as illustrate here.

    For example, an "n = 4" or nH2O chain is: ++(H2O)(H2O)(H2O)(H2O)-- and splitting it into ++(H2O)(H2O)(NO3)-- etc. takes energy* but the 4H2O chain is not 1D linear as illustrated. it is 3D. As thee chains and simple H2O molecules collide they are constantly breaing and others are adding an ++(H2O)-- to grow longer in a dynamic equilibrium with a fixed distribution of n at any temperature. As water cools, the average n increases. This explains why water cooing below 4C expands. I.e. the average "void volume" as a "jumble" of chains grows colder in creases below 4C.

    * Perhaps if this "busting of chains" did not happen, there would be no cooling of the water (when NH4NO3 molecule dissolve)?
    Last edited by a moderator: Sep 12, 2013

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