How do some molecules stay together, and others stay apart?



Everything is made out of molecules, including your palm and the wall next to you. If you put your palm on the wall, it won’t stick. You can pull it off very easily. But if you try the same thing with your finger, and attempt to pull it off of your hand, you can’t do it easily, and if you managed to do it you couldn’t put it back by just placing it there. What changed, and why do some molecules stay connected while others don’t?

In: Physics

Are you talking about ripping your finger off your hand?

What? There should be little difference to the adhesive and cohesive properties between the skin of your finger and of your palm, so I have no clue where your anecdote is coming from.

As for your question, some molecule have more pronounced “dipoles”, or distributions of charge where it’s slightly more positive on one side, and slightly more negative on the other. This can cause an attraction to other similar dipoles, which can make things sticky. If the substance doesn’t have those dipoles, it’s not going to stick.

Your example has nothing to do with molecules.

But to answer your molecular question, there are 3 forces which bring molecules together, ionic force (essentially the reason we say opposites attract in science), dipolar force (similar cause, but more like magnets where one end is + and the other -, and what’s known as London Dispersion (when within a molecule there are regions of + and – and they attract to other molecules with regions of similar strength +/-. If these forces are not present between molecules they don’t “stay together”.

Intermolecular forces hold atoms and molecules together. The charge of electrons on the outside of molecules that make up each item, repel each other