A polar bear and a penguin are having a heated debate, about the intermolecular forces and which of the many is best. "The ion-dipole forces are clearly best," says the polar bear. "It is between an ion and a polar molecule. It's partly the reason why salt dissolves in water and the sodium and chlorine stay apart." "You, sir, are incorrect," proclaims the penguin. "The dipole-dipole forces are much better. Dipole-dipole forces are one of the reasons why polar molecules have varying but consistent boiling points instead of random boiling points."
For no reason, right in the middle of the debate, the polar bear suddenly stops talking and looks stumped. "What's wrong?" inquires the penguin. After a moment more of pondering, the polar bear gets close to the penguins face and asks, "What do you know about thermodynamics?" The penguin's face turns from query to annoyance and stale emotion; the penguin cannot respond, for the penguin is a nonpolar molecule.
This will help clear some confusion. This whole joke, albeit better written, came from my chemistry class at school. Before the discussion, the class's 'pets' were the penguin and the polar bear. The polar bear represented a polar molecule, and the penguin a nonpolar molecule. It was brought up today, the polar bears and penguins because intermolecular forces deal very heavily with polar bonds.
The first joke is that the polar bear should not be debating for ion-dipole, it should be debating for dipole-dipole. Vice versa goes for the penguin. The second is that in thermodynamics, nonpolar bonds are not as common as polar bonds, so when asked about the concept, the nonpolar penguin can't say much and becomes annoyed. Even if you don't laugh at it, I hope the joke and this explanation of the joke teach you a little chemistry.