We often think that boiling water must be hot, after all, it’s boiling! But that isn’t exactly true. You can actually boil water all the way up to the point that it freezes – but only under the right circumstances.
What we know as water’s boiling point, 212˚F, is actually its boiling point at atmospheric pressure. When the pressure surrounding water is changed, so does it’s boiling point.
If you place a glass of water inside a vacuum chamber and start sucking out all the air, at some point, the water will start boiling without you having to heat it up at all. By removing the air, you are changing the boiling point of the water and as it drops below the current temperature of the water, that’s when the reaction starts occurring.
But something a little peculiar happens when you continue boiling the water under vacuum. The most high energy water molecules, or the hottest ones, begin escaping as water vapor, like any other time you boil water. This, in turn, ends up cooling down the water as the pressure continues to drop. So, as the boiling process continues, the water constantly loses more and more heat. If you continue running the vacuum pump, eventually, the water will drop below it’s freezing temperature and freeze.
Still, don’t believe all this perplexing science? Check it out explained by Cody’s Lab in the video below.