Liquids occupy a rather peculiar place in the trinity of solid, liquid and gas; like solids, their molecules are in direct contact, and so their densities are similar, but the abilitiy of their components to slip and slide around each other gives liquids something of the mobility of a gas. From the standpoint of chemistry, this represents the best of two worlds; rapid chemical change requires intimate contact between the agents undergoing reaction, but these agents, along with the reaction products, must be free to move away to allow new contacts and further reaction to take place. We also recognize the liquid as being the preferred state of a substance at temperatures intermediate between the realms of the solid and the gas. But if you look at the melting and boiling points of a variety of substances, you will notice that the temperature range within which many liquids can exist tends to be rather small. In this, and in a number of other ways, the liquid state appears to be somewhat t