Strength of intermolecular forces

[JTieu_1L]

What does this mean "The reason for the very rapid falling off of the dipole–dipole interaction is that as the distance between molecules increases, the opposite partial charges on each molecule appear to merge and cancel, whereas in the interaction between a point charge and a dipole, only the partial charges on the dipole appear to merge."

[BrittneyMyint1D]

I'm a bit confused on the last half of the sentence,, but I believe what the first half is trying to say is that as the distance increases between the molecules, the strength of the dipole-dipole interaction will decrease. Hope this helps!

[IanWheeler3F]

I think what it means is dipoles are only temporary and can merge to become neutral, so in the case of two dipoles when they are separated from each other the two dipoles stop reciprocating charge with one another. But a point charge (like an ion) is ALWAYS a point charge no matter how far away it is moved away from a dipole, so only the dipole's partial charges will merge, but not the point charge's charge.

[Samudrala_Vaishnavi 3A]

Distance plays a huge role in determining the strength of dipole-dipole interactions since this increases the bond length between them making the interactions weaker (the measure of the interactions is divided by the distance cubed). If the dipole was interacting with an ion, however, there is a greater difference in electronegativity to the point in which there is still interactions between the dipole and the ion regardless of the distance and the charge of the ion is almost unaffected while the dipole may loose its partial charges (delta positive and negative) like with dipole-dipole interactions.