The water-containing flask has been partially evacuated, allowing the water inside to fall as one solid column. (Typically water breaks up as it falls through air, due to drag.) The sound made when the water hits the bottom is quite remarkable.
To use: hold the flask vertically with the bulb at the top. Quickly shake the flask up and down once. When the water hits the bottom it sounds (and feels!) more like a solid metal object than a fluid. In fact, I’m convinced that the flask would break if shaken hard enough, though the information sheet doesn’t caution against it.
Evacuate chamber with vacuum pump and water boils.
Explanation: Room temperature water contains enough energy to boil but won’t because atmospheric pressure pushes in on the liquid from all sides, preventing vapor bubbles from forming.Remove pressure and water will boil.
