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Quantum Physics and the Real World

  1. Feb 6, 2005 #1
    Quantum Physics and the "Real" World

    Could it be argued that the four energy levels of an atom relate to states of matter in our macro world?

    For example something is a solid, then you bump it up an energy level and it becomes liquid, bump it up again and it becomes gas, again and it becomes plasma.

    I know there are more than 4 states of matter but the others could be considered intermediate steps.
  2. jcsd
  3. Feb 6, 2005 #2
    A solid/liquid/gas/plasma is qualified as such on the basis of the interaction between its constituent atoms (or molecules). It has nothing to do with the internal energies of those atoms themselves. It does, however, relate to their thermal (kinetic) energies, which are a different matter.
  4. Feb 6, 2005 #3
    so the interaction between the molecules change but it has "nothing to do with the internal energies of the atoms themselves"?

    Are you sure about that?

    What then causes the change in the interactions? I would think the interactions are different because some change has occured. Remember that heat is no the only player in the "state of matter" game. Pressure also plays a role as do electrical forces.
  5. Feb 6, 2005 #4
    A quantum state is one of a set of a complete set of states. A complete set of states is one where they are all orthonormal and form a basis for the state space. This means that the set completely defines the possible states for the system.

    The states of matter (i.e. liquid/gas etc.) is a completely different notion to that of quantum states, since these states do not completely define the possible states of the system.
  6. Feb 6, 2005 #5


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    What 4 energy levels are u talking about...?

    Tell me 'bout the 4 energy states of an atom and i'll tell u then if they have anything to do with the "macro" world...

    What energy level??Is there a physical term for the syntagma:""bump it up"??

    What do you know about phase transitions...??

  7. Feb 6, 2005 #6
    By energy level I mean the n number in Bohr model. The principle quantum number.

    By "bump it up" I mean raise the energy level. Increasing the n value.
  8. Feb 6, 2005 #7


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    And what would that # have to with
    1.4 values ??Of whom...?
    2.Phase transitions.


    EDIT:Thanksguys,that was close... :smile:
    Last edited: Feb 6, 2005
  9. Feb 6, 2005 #8
    1. From Wikipedia -"

    The Principal quantum number (usually written n) is the first quantum number of an atomic orbital. It represents the relative overall energy, and hence also the average distance from the nucleus, of an orbital. The sets of orbitals with the same n-value are often referred to as electron shells or energy levels.

    * The atomic orbitals with n=1 are said to be in the 'K'-shell
    * The atomic orbitals with n=2 are said to be in the 'L'-shell
    * The atomic orbitals with n=3 are said to be in the 'M'-shell
    * The atomic orbitals with n=4 are said to be in the 'N'-shell

    2. Yes that is my question. Do these discrete energy levels represent discrete states of matter in our macro world?
  10. Feb 6, 2005 #9


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    IIRC,there can be an infinity of values for "n",and all would correspond to discrete energy levels in the negative semiaxis...

    As for the second...No,no connection whatsoever...

  11. Feb 6, 2005 #10
    IIRC In THEORY n can be any number (the math works out with any number) but in actuality n is usually a low number because the "atom" or atom wave loses coherence at progressively higher numbers.
  12. Feb 6, 2005 #11


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    That's still not a reason for restraining to 4 values for "n"...Should i remind you that we discovered atoms with electrons in the 7-th shell...?

  13. Feb 6, 2005 #12
    Perhaps the following simple comparison will demonstrate the differences:

    Binding energy of hydrogen in ground state: 13.6eV
    Difference to first excited state (n=2): 10.2eV

    Energy needed to melt ice to water: ~0.06eV / water molecule.

    Corresponding energy levels on the atomic scale occur at n~15 in hydrogen (higher values still for heavier nuclei), which are incredibly unstable and make no contribution to the atom's behavior. In short, the energy scales are clearly different.

    The interactions between the constituent atoms or molecules of a pure substance are quite intricate. In a solid, the atoms are densely packed and locked in place, more or less. In a gas, the particle density is low enough to make interactions largely negligible and reducible to ensemble properties. (By this I mean that in a gas there is no preferred interactions between molecules, while in a solid interactions with the atom's neighbors dominate the behavior). The liquid phase lies somewhere in between and is in fact quite difficult to describe. However, other than the temperature-induced variation, there is no significant change in the population of higher atomic energy states between something in solid, liquid, or gas form.
  14. Feb 6, 2005 #13


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    Solid, liquid, etc... are NOT "four energy levels of an atom". They are difference phases of matter. They transforms from one phase to another via a "phase transition". This isn't simply a different "energy level", but a complex series of many-body processes.

  15. Feb 6, 2005 #14

    Hans de Vries

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    Using the energy is a good way to compare the two.
    Matter starts glowing when atoms become exited....

    Regards, Hans
  16. Feb 7, 2005 #15

    Thanks zefram that is pretty much what I was looking for.
    Just a couple of follow up questions if you dont mind. For example how much energy to the next excited states for hydrogen (3,4,...) as well the energy need to bring about phase changes in hydrogen (you cited water which is far more stable)

    Normally we consider that photons are given off when the energy level changes could infra red radiation (heat) also be given off or be given off instead?

  17. Feb 7, 2005 #16
    Well, I cited water b/c I have that value off the top of my head.

    The value for hydrogen is courtesy of www.webelements.com : 0.558kJ/mol = 0.006eV (one full order of magnitude lower)

    Since it seems you don't know how to get the energy levels of hydrogen (this can be found in your favorite introductory QM book or first year chem book, sometimes even in physics texts under Rydberg constant), suffice it to say that E(n) = 13.6eV / n2.

    From there you can take differences between energy levels: E(n)-E(m) = 13.6eV( 1/n2 - 1/m2 ).

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