Inspired by this thread.
To sum up that thread, everything is mostly nothing, but nothing can go through anything else because of repulsion of atoms. But my question doesn’t really have anything to do with that. Obviously, when I put my hand into some water, it isn’t going through it, it’s displacing it* (Eureka and all that). So why do liquids act like that? What gives them their liquidity?
Liquids are held together by chemical bonds that aren’t as strong as those holding solids together.
A chemist will, I’m sure, be along in a moment to explain things more completely, but the basic idea is that there is a big range in the strength of chemical bonds that keep stuff together. At the strong end is covalent bonds, which are more like intramolecular forces than intermolecular ones, essentially making large chunks of the substance hold together with the same strength that a molecule of it does. Diamond is one example of this.
A bit weaker are dipole bonds/hydrogen bonds, which are due to the fact that some molecules like water aren’t symetrical in their charge distribution. Oxygen is more negative and Hydrogen more positive, so the slight positive on the H of one water molecule is attracted to the slight negative on the O, and they tend to clump together. Water has relatively strong bonds of this sort, because Oxygen is strongly electronegative. A dipole bond between H and O, F, or, uhm N (?) is considered a hydrogen bond, but it’s really the same thing as any dipole bond.
Way down at the end, you have Van der Waals forces, which are between molecules that aren’t dipolar. However, because molecules aren’t exactly static, they will experience periods of slight polarity that cause a very weak attraction.
I probably left out a lot of important stuff.
Gah. Sorry. Van der Waals’ is a larger category that includes both the dipole bonds I mentioned and the weak temporary dipole stuff.