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Is polar attraction stronger than the repulsion of electrons?

  1. Jan 16, 2013 #1
    So if any subtance has theoretically 0 degrees kelvin, it will be a solid, correct? So does that mean that tempurature is the main factor that determines state of matter? What i mean to ask is, why would non polar molecules want to be close together like in a solid, when really, the electrons in the outer shell of each molecule would just want to repell the separate molecules away from eachother?
  2. jcsd
  3. Jan 16, 2013 #2
    Temperature is a big factor, but for normal phases, such as solid, liquid and gas, pressure is also very important.

    A system may be solid at one temperature, and liquid at another temperature, if the pressures are different.

    About your other point, I would recommend you read about van der waals forced to learn about induced dipoles. You may also be interested in knowing helium remains liquid down to absolute zero at normal pressure.
  4. Jan 17, 2013 #3
    I think if your looking for mysterious happenings in the atomic-subatomic world, this is one of the less mysterious. Temperature does have an effect on the state of matter by jiggling atoms around and overcoming the bonds that would make it solid. That's pretty straightforward. And electrons typically do not want to be around each other if they don't have to. They form solids and liquids mainly because of the coulombic attraction of atoms which are ions in isolation so that each mutually attract a pool of electrons that get shared amongst them. That's where the solid comes from and it is the positive attraction from the nuclei that overcome any repellant effect of the electrons on each other.
  5. Jan 17, 2013 #4
    Approaching zero kelvin means that there is a large (approaching infinite) change in entropy with respect to a change in heat to the system. I perceive this to mean that there is a lack of micro states, even though this COULD be any constant I prefer to think that the discrete nature of energy is indicative that there cannot be an infinitely small change in entropy with respect to an infinitely small change in heat. I think that this is a point where the approximation we make using calculus fails.

    This leads to only a single conclusion in my mind and that is that the micro state must be changing from 0 to 1 for a finite and measure able change in heat resulting in an infinite resultant change whereas any other micro state count for a finite change in heat is a finite value.

    So I don't think it is possible to have a zero kelvin system and a dipole since a dipole would require a difference in charge over some distance and I don't believe there are any fundamental particles that are not uniformly charged.

    As for very low temperature which I'm sure you are referring let's again look at the fact that the change in entropy is very large for any small change in heat. Suppose we have a system of charged particles that are equidistant and far enough apart that their gravity and electrostatic forces are essentially balanced. Would you consider them a solid given this relative rigidity?

    Now consider a slightly different system where instead of considering gravity as a factor we had some flexible barrier that all of the particles are repulsed by. Wouldn't it make sense that a similar system as the one above would form where the particles would reach some relatively equidistant equilibrium to balance their electrostatic repulsion with respect to the applied forces from the flexible barrier?

    So wouldn't it make sense that the volume enclosed by this barrier depends on the pressure that the flexible barrier exerts inward. Which is telling us the magnitude of the forces involved. So then wouldn't it make sense that the greater the forces involved the more energy it would take significantly perturb a particle to cause a significant change in the system. No this isn't entirely true but I think it is a good way to think about solid, liquid, and gas states as ease in which to cause mobility.

    For a realistic system things are more complex geometries but I think the same basic idea holds although there is not dimension symmetry and even lower energy perturbations can cause mobility. But even for a polar molecule I want to point out that there are complex geometries involved so you can't treat them as if the electron cloud causes polar symmetry and even solids have constant vibration.
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