A thermometer or thermocouple can be added to show temperature. 4C30.10 boiling cold water H-5d Heat water to boiling in a round bottom flask, stopper, invert, pour cold water over to maintain boiling. Disc 15-10 Boil water in a r.b. flask with a dimple in the bottom, remove from heat, stopper, invert and add ice to the dimple. A thermometer measures the boiling point as a vacuum pump is used to reduce the pressure in a flask of water. Pump on a flask of warm water with aspirator or vacuum pump until boiling starts.
Water is superheated in a very clean flask free of flaws.
A similar flask with boiling water is nearby. Add chalk dust to the superheated water and boiling starts explosively. A long tapered tank is used to form a geyser. 4C30.25 geyser H-5e Picture of a geyser demonstrator. Heat a corked test tube or make a bomb by sealing off some water in a glass tube and heating it.