Saturn has a watery moon

The recent images of a Saturn moon show it spewing ice and water into the outermost ring of the planet. Since there is not much gravity in the moon, most of the volcanic stuff goes up and then doesn’t come down. There is one thing that seems confusing to my non-scientific mind:

You need quite a lot of energy if you are going to produce these geysers, and water boiling off into a vacuum is a good way to do that. If you expose liquid water to a vacuum, it boils explosively and it freezes at the same time. And so it’s a pretty violent event. The boiling point becomes equal to the freezing point. So you get this very explosive boiling and freezing. So that’s plenty of power to shoot stuff off the moon.

How can boiling point be equal to freezing point when heat is totally the opposite of cold? I mean, if heat is an energy, then isn’t cold the opposite of it? Hmmm…I would love to know some opinions.