Are intermolecular and van der waals forces the same?

In summary, van der Waals forces are interactions between neutral atoms due to their dipole moments, and are considered weak compared to forces between charged particles. While all forces of interest are ultimately electromagnetic, quantum field theory may be needed to fully explain them. The application of an external electric field can modify the van der Waals effect, but the original description would have to be adjusted to account for it.
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are intermolecular an van der waals forces the same thing? I am doing a physics assignment on surface tension and am unsure of what forces are present. i know that there is hydrogen bonding, but what else? thanks
 
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  • #2
all the forces of interest are ultimately electromagnetic.

van der waals forces are a way for atoms which are overall neutral to still interact and are due to the fact that even a neutral atom can have a dipole moment, and the interaction of two dipole falls off like the sixth power of the distance. So those forces are generally considered weak (since they fall off fast) compared to forces between charged things.

P.S. if there's a homework assignment related to this question then maybe this thread should have been posted in the homework forums...
 
  • #3
While all the forces of interest are ultimately electromagnetic, it's not clear that they can all be explained with classical electromagnetism. One may need to go to quantum field theory to explain all the details of electromagnetic forces. The Casimir force is a good example of a force explainable only with QFT. I know that surface tension was a mystery for a long time, suggesting to me that it's explanation may require more than classical E&M (otherwise it wouldn't have been such a mystery).

I recall hearing that QFT resolved some of the questions with surface tension, but I don't recall where I read this, it may not have been a reliable source :-(.

Sorry to post when I don't have a definite confirmed answer, but I think the question is an interesting one, and I'd like to get a better handle on it myself.
 
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BTW, Chaiken and Lubensky's Solid State book discusses van der waals forces in one of the first few chapters. Probably has a lot of good stuff on surface tension, etc.
 
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Can application of an outside E-field modify the van der Waals effect?
 
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Are you asking me, or pervect? Should this question be a new thread? The OP hasn't had much of a chance to respond yet to the answers given to his question...
 
  • #7
It certainly can wait until more responses address the original concern.
 
  • #8
Loren Booda said:
Can application of an outside E-field modify the van der Waals effect?

Certainly applying an external electric field will have an effect on a collection of atoms and the description of the interactions will have to account for it... the original description, if in terms of van der waals alone, should have to be modified.
 

What are intermolecular forces?

Intermolecular forces are attractive or repulsive forces between molecules. These forces are responsible for the physical properties of substances such as melting point, boiling point, and viscosity.

What are van der Waals forces?

Van der Waals forces are a type of intermolecular force that results from the interaction between temporary dipoles in molecules. These forces are relatively weak compared to other types of intermolecular forces.

Are intermolecular forces and van der Waals forces the same thing?

No, intermolecular forces and van der Waals forces are not the same thing. Intermolecular forces refer to all types of forces between molecules, including van der Waals forces. Van der Waals forces are a specific type of intermolecular force.

What is the difference between intermolecular forces and intramolecular forces?

Intramolecular forces refer to the forces that hold atoms together within a molecule, such as covalent bonds. Intermolecular forces, on the other hand, refer to the forces between molecules. These forces are generally weaker than intramolecular forces.

How do intermolecular and van der Waals forces affect the properties of substances?

Intermolecular and van der Waals forces can affect the physical properties of substances by influencing the degree of attraction between molecules. These forces can impact properties such as melting point, boiling point, and solubility.

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