“What causes liquids to stick together?”
Liquids are a most peculiar state of matter. Their shape will change depending on the container that they’re in (just like gases) , but at the same time their volume will remain consistent (just like solids). Why do liquids have this paradoxical combination of features? Well, let’s investigate it. On a microscopic level, the molecules of liquids move around in semi-free state, not being as rigidly bound as a solid but not having the level of separation as a gas. The molecules of a liquid are attracted to one another through a phenomena known as cohesive forces, in which molecules of the same type experience an intermolecular force attracting one another. Now with this fact, we can deduce something very interesting. Volumes of a material are composed of units of molecules. And since molecules in liquid experience cohesive forces that makes them stick together, the amount of molecules in this liquid will not change unless a more powerful force rips away some of the molecules, therefore giving liquids a constant volume! Due to cohesive forces, liquids can be fluid like gases but maintain their volumes when poured into another container or experience mechanical stresses, or exhibit properties such as surface tension.