Mechanical properties of solids questions

[Mandavi]

Homework Statement

Intermolecular forces are
1- Attractive only
2-Repulsive only
3-Long-range
4-Short-range

Homework Equations

The 1st and 2nd options are not valid as the nature depends on the distance between the molecules.

The Attempt at a Solution

The answer given is short-range.How is that?Even,at infinity,the force does not become zero as even then,attractive forces should act.Or is it so,because intermolecular distances are measured on a very small scale and therefore,they are not valid for long distances?

 

[Mandavi]

This is another question from the same topic.
"In a solid,the kinetic energy of molecules is less than the magnitude of their potential energy."
How did we come to this conclusion?I know it is true for an atom,but why do we say this for molecules of a solid too?

 

[tomcue]

I would like to clarify the concept of intermolecular forces and their nature. Intermolecular forces are the attractive and repulsive forces that exist between molecules. These forces are responsible for the physical properties of solids, such as their melting and boiling points, as well as their strength and rigidity.

In answer to the given question, the correct option is short-range. This means that intermolecular forces act only over a short distance between molecules, typically on the order of nanometers. At longer distances, these forces become negligible and do not have a significant effect on the overall behavior of the solid.

It is important to note that intermolecular forces are not limited to only attractive or repulsive forces. They can be both attractive and repulsive, depending on the distance between molecules. At very close distances, the forces are repulsive as the molecules are too close to each other. However, at slightly larger distances, the forces become attractive as the molecules are able to interact and form bonds.

The reason for the short-range nature of intermolecular forces is due to the fact that they are based on electrostatic interactions between molecules. These interactions weaken rapidly with distance, making them negligible at longer distances. Additionally, the size and shape of the molecules also play a role in determining the strength and range of these forces.

In conclusion, intermolecular forces are both attractive and repulsive, but their nature is dependent on the distance between molecules. They are considered short-range because they are only significant over a short distance and become negligible at longer distances.