Physics

Water has no fixed boiling point

Water has no fixed boiling point. It boils when its upward vapor pressure matches the pressure pushing down on it, so less pressure means a lower boiling point. On top of Mount Everest, where the air presses with about a third of its sea-level force, water boils near 70C, too cool to cook an egg.

Sources & further reading

OpenStax (Rice University)10.3 Phase Transitions (Chemistry 2e)The textbook rule that water boils when its vapor pressure matches the pressure around it, so the boiling temperature moves with the surrounding pressure.National Institute of Standards and TechnologyNIST/ASME Steam Properties (NIST Standard Reference Database 10)The government reference tables that list exactly what temperature water boils at for any given pressure.CK-12 FoundationWhy can't we boil an egg on Mount Everest?The explainer behind Everest's roughly 70C boil and why an egg will not cook in it.Summit Racing EquipmentWhy is the cooling system under pressure?The engineering explainer showing a pressurized radiator raises coolant's boiling point so the engine can run past 100C without boiling over.Encyclopaedia BritannicaDenis PapinThe record of Denis Papin's 1679 sealed steam digester, the ancestor of the pressure cooker and the autoclave.Centers for Disease Control and PreventionGuideline for Disinfection and Sterilization in Healthcare Facilities (2008)The CDC guideline that hospitals sterilize with pressurized steam near 121C to kill even bacterial spores, with prions as a known exception.USDA Food Safety and Inspection ServiceClostridium botulinum & BotulismThe federal food-safety rule that low-acid foods need pressure canning near 116 to 121C, because botulism spores survive plain boiling.