Duration: 4:12 User: n/a - Added: 10/9/12 Once the pump is turned on and the pressure reduces, the water in the beaker starts boiling violently, and then suddenly freezes. The reason why the water freezes is that O when the water boils, it takes energy from the liquid water to remove water molecules from the liquid. This cools the liquid water down until it freezes at OC. O water in a vacuum is not stable, and so the water freezes at room temperature. O all the liquid water boils away, leaving frozen water in the beaker. O the glass beaker rapidly cools in a vacuum until the water freezes at OC