Is polar attraction stronger than the repulsion of electrons?

AI Thread Summary
Temperature is a key factor in determining the state of matter, but pressure also plays a significant role. At absolute zero, substances theoretically become solids, yet non-polar molecules can still exhibit solid-like behavior due to the attractive forces between their nuclei, which can overcome electron repulsion. The discussion highlights the importance of van der Waals forces and the concept of induced dipoles in understanding molecular interactions. Additionally, the relationship between entropy and temperature changes is emphasized, suggesting that even small temperature variations can lead to significant changes in a system's state. Overall, the interplay of temperature, pressure, and intermolecular forces is crucial in defining the phases of matter.
jaydnul
Messages
558
Reaction score
15
So if any subtance has theoretically 0 degrees kelvin, it will be a solid, correct? So does that mean that temperature 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 each other?
 
Physics news on Phys.org
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.
 
So does that mean that temperature 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.

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.
 
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.
 
This is from Griffiths' Electrodynamics, 3rd edition, page 352. I am trying to calculate the divergence of the Maxwell stress tensor. The tensor is given as ##T_{ij} =\epsilon_0 (E_iE_j-\frac 1 2 \delta_{ij} E^2)+\frac 1 {\mu_0}(B_iB_j-\frac 1 2 \delta_{ij} B^2)##. To make things easier, I just want to focus on the part with the electrical field, i.e. I want to find the divergence of ##E_{ij}=E_iE_j-\frac 1 2 \delta_{ij}E^2##. In matrix form, this tensor should look like this...
Thread 'Applying the Gauss (1835) formula for force between 2 parallel DC currents'
Please can anyone either:- (1) point me to a derivation of the perpendicular force (Fy) between two very long parallel wires carrying steady currents utilising the formula of Gauss for the force F along the line r between 2 charges? Or alternatively (2) point out where I have gone wrong in my method? I am having problems with calculating the direction and magnitude of the force as expected from modern (Biot-Savart-Maxwell-Lorentz) formula. Here is my method and results so far:- This...
Back
Top