(Chem; Phys; Abb: bp) The temperature at which a liquid becomes a vapor or gas, or at which the vapor pressure of the liquid is slightly higher than the pressure exerted on it by the surroundings. This temperature is pressure-dependent, and remains constant as long as any liquid remains to boil. Normal boiling point is the boiling temperature of a liquid under atmosheric pressure. For mixtures that do not have a constant boiling point, a distillation may be performed. Also called: Vaporization Point. See also: Vapor Pressure;Heat of Vaporization; Ebulliometry. Note: The boiling point of a liquid can be determined by noting the temperature at which bubbles of vapor first appear as the liquid is heated. This is an approximation, since the bubbles may be formed by dissolved gases or other impurities. Every substance that has a liquid state has a more-or-less unique and characteristic boiling point. Hydrogen, for example, has a bp of - 252°C; water, 100°C; and titanium, 3260°C