Not to mention, if water is pure and still enough, you can cool it below freezing point, and it still looks like a liquid, until it is disturbed and then it suddenly doesn't. Same with heating up above boiling point.
Also with heating?
So all the bubbles rising up way before boiling and the visible evaporation does not happen with distilled water? Hard to believe, I have to say. You would have to do perfect even heating of all the water, to stop the movement from different temperate areas. Microwaving it?