Energy levels are one thing, but liquids are just a fundamentally unstable state of matter. Absent external pressures, they will either evaporate or freeze depe

Energy levels are one thing, but liquids are just a fundamentally unstable state of matter. Absent external pressures, they will either evaporate or freeze depending on temperature. Most likely, with very low atmospheric pressures such as in the vacuum of space, the outer parts will quickly vaporize, consuming energy from the inner parts which will then freeze. Basically, some amount of a liquid will move to the higher energy state, and other parts will move to a lower energy state. The energy to vaporize some of the liquid doesn't need to come from something external to the liquid.