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Particles in objects are constantly exchanged w/ particles in environment

  1. Sep 12, 2011 #1
    I read or watched a documentary a long time ago that explained that the particles in any given object are constantly being exchanged with particles in the surrounding environment. i.e. the particles of matter that make up a table are constantly being added to and taken away, exchanged with the environment, so that the table has none of the same particles over time that it originated with.

    I'm wondering if anyone knows anything about this and can point me in the direction of more information about it.

    Also, if anyone knows of any sources on the topic of how the particles in the table keep themselves in the shape of the table, that information would be useful as well.

    Thank you. This is my first post here and am thankful for any comments.
     
  2. jcsd
  3. Sep 12, 2011 #2

    Ken G

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    That sounds like living organisms, not tables-- tables in a N2 gas would seem to be pretty inert I would think. They might mean electrons tunneling from atom to atom, but I don't think that happens very quickly, I don't know if that's what they meant.
     
  4. Sep 13, 2011 #3
    Thanks, Ken G. It's possible that it was discussing electron sharing but it's been so long since I either saw or read about the topic that I don't recall exactly what was being said. I appreciate your input.
     
  5. Sep 13, 2011 #4
    I'm not sure about a wooden table, but the phenomena you describe is fairly common in phase exchange situations. Let's say your table is made of ice at a temperature of -25°C. This surface of ice is in a state of equilibrium with an atmosphere of water vapor.

    That surface would receive some 2.51 x 10^24 vapor molecule impacts per square meter per second. The general assumption is that most (if not all) of these molecules "stick". Since we have equilibrium, the same number leave that ice surface in one second. Since there will be 9.81 x 10^18 surface molecules per square meter, this means that each surface molecule is "replaced" some 256 thousand times each second.

    This "replacement" in not all due to the "newcomers". Many of the surface molecules will be replaced by adjoining molecules just below the surface. And many of the newcomers will have sufficient kinetic energy of translation to penetrate below the surface molecular layer of the ice.

    As for the ice table keeping its shape, the same intermolecular binding forces that kept the departing molecules in place will apply to the newcomers as well.
     
  6. Sep 13, 2011 #5
    Some of this sounds like a badly misunderstood explanation of force carriers. In quantum mechanics, forces are mediated by a constant exchange of virtual particles. These virtual particles are not the particles that an object is made of, they are "incomplete" particles that last only a brief time, traveling between the particles making up normal matter and carrying the forces holding things together. Sound familiar at all?
     
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