Why are ice molecules arranged in a way in which there are empty spaces in the ice structure?
In a liquid there is enough energy so that the molecules can be higeldy-pigeldy. That said, there are still attractive forces between the electro-positive hydrogens and the electro-negative oxygens, they’re just overpowered by the kinetic energy. When you cool water to just below freezing point all that kinetic energy is sapped away, leaving (for all intents and purposes) only the dipole-dipole force as described. These water molecules want to fall into a geometry that allows the strongest bonds possible. It turns out that given the angular shape of H2O, the hexagon is the most stable. To answer your question, if you have a bunch of angular stick and ball models, which arrangement would take up more room: all the models bunched up together like in a liquid or spread out to form a hexagon like in ice?
