Question

actually..what is intermolecular force?

Answer 1

INTERmolecular forces are forces between molecules, and INTRAmolecular forces are forces within a molecule :)

Answer 2

how to differentiate between intermolecular and intramolecular force?

Answer 3

well it really depends on what you are looking for... but if you remember this:

Intermolecular forces from strongest to weakest: hydrogen bonding, dipole-dipole interactions and dispersion forces.

Intramolecular forces from strongest to weakest: ionic bonding, covalent bonding and metallic bonding

but just to reiterate: intermolecular is between two molecules, say H20 and H20 and intramolecular would be between Hydrogen and Oxygen within this molecule! :)

Answer 4

ok..but can you explain more about hydrogen bonding,dipole-dipole intractions and dispersion forces?

Answer 5

well, hydrogen bonding is when hydrogen is bonded to either fluorine, oxygen or nitrogen.
dipole - dipole interactions are when molecules take up a partial positive or partial negative charge and bond due to electrostatic attraction.
dispersion forces are due to momentary partial positive or negative charges and this is due to uneven distribution of electrons. The more electrons that are present, the stronger the dispersion forces

Answer 6

The only essential distinction of intermolecular forces is that they do NOT lead to covalent chemical bonds. Since a chemical bond is a strongly quantum-mechanical effect, what this means is that intermolecular force are not new forces in any sense, they are just the purely classical "leftover" effects of the same electric forces that lead to chemical bonding.

For example, it's a fact that systems that are electrically neutral but polarizable attract each other. The reason is that every time system A is momentary polarized (because, say, the electrons are momentarily more on one side of the nucleus than the other), it will act to induce polarization in B. (The excess negative charge on one side of A will repel the negative charge on B, making it flee to the opposite side of B, and therefore turning B polar.) What is crucial is that this then produces a slight attraction between the momentarily polar A and B, and they will move slightly closer, which then increases the effect (because the electric forces they exert on each other get stronger as they get closer).

Now, if either system doesn't have a "closed shell" electron configuration, then as the systems come closer the quantum effects will significantly increase the polarization and powerfully enhance the attraction. This is how a chemical bond forms. But if the systems are closed shell -- because they started out that way, like noble gas atoms, or because they are molecules with satisfied octet rules, et cetera, then the quantum effects cannot come into play to deepen the attraction, and it remains modest, something fairly easily overcome by the everyday motion of atoms and molecules at room temperature.