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Claim analyzed
Science“Water can simultaneously boil and freeze under specific pressure conditions.”
The conclusion
The claim is scientifically accurate. At water's triple point (~0.01°C and ~611 Pa), solid, liquid, and gas phases coexist in equilibrium, meaning the conditions for both boiling and freezing are simultaneously met. This is confirmed by NIST, peer-reviewed research, and multiple academic sources. The minor caveat: "simultaneously boil and freeze" slightly overstates the drama — it's thermodynamic equilibrium coexistence, not necessarily vigorous concurrent boiling and freezing — and the required pressure is just 0.6% of normal atmospheric pressure.
Based on 18 sources: 18 supporting, 0 refuting, 0 neutral.
Caveats
- The required conditions are extremely specific: ~611 Pa (~0.006 atm), roughly 0.6% of normal atmospheric pressure — this is a laboratory phenomenon, not something encountered in everyday life.
- "Simultaneously boil and freeze" is colloquially vivid but technically refers to thermodynamic equilibrium where all three phases coexist; in lab demonstrations, the transitions can appear sequential rather than dramatically concurrent.
- This applies only to pure water; dissolved solutes shift the triple point conditions.
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Sources
Sources used in the analysis
The kelvin is defined as the thermodynamic temperature of the triple point of water, which is exactly 273.16 kelvins (K). The triple point of water is the condition in which water exists simultaneously in solid, liquid, and gaseous states.
The vapor pressure of water at its triple point was measured with exceptionally high accuracy... Actual triple point conditions were established with a thin sheet of freshly distilled liquid flowing down over an exposed mantle of ice frozen on a vertical well.
The triple point of water is the unique combination of temperature and pressure at which the solid phase, liquid phase, and gaseous phase can all coexist in thermodynamic equilibrium. By international agreement, the triple point of water has been assigned a value of 273.16 K (0.01 °C; 32.02 °F) and partial vapor pressure of 611.66 pascals (6.1166 mbar; 0.0060366 atm).
When all three phases are present and in equilibrium, the temperature and pressure condi- tions at which this occurs is called the “triple point”. The triple point of water in the absence of air occurs at a temperature of 0.16o C and a pressure of 4.58 mm Hg.
A phase diagram shows the preferred physical states of matter at different temperatures and pressure. The phase diagram of water is complex, having a number of triple points and one or possibly two critical points.
At the low pressure of 611 Pa (only 0.006 times atmospheric pressure), pure water boils at 0.01 °C, and it also freezes at 0.01 °C. The combination of conditions (P, T) = (611 Pa, 0.01 °C) is called the triple point of water because, at this pressure and temperature ice, liquid water and steam can coexist in equilibrium.
At the triple point, vapor, liquid, and solid coexist in equilibrium. For water, this occurs at low pressure (0.006 atm) and 0.01°C. This is the point where the solid-liquid, liquid-gas, and solid-gas lines meet.
The triple point of water occurs at a temperature of 0.01 °C and a pressure of 0.00603659 atm. At this intersection of temperature and pressure, water molecules exhibit a unique equilibrium where they exist simultaneously as solid ice, liquid water, and water vapor.
At the triple point—0°C and 611 pascals—water can exist as ice, liquid, and vapor simultaneously. In the lab, scientists show it with a sealed glass tube of pure water. A pump pulls the air out, lowering the pressure until the water boils—even though it's cold. As it bubbles, the heat loss is so great that the rest freezes into ice. You can literally watch boiling and freezing side by side, in the same container.
The triple point occurs where the solid, liquid, and gas transition curves meet. The triple point is the only condition in which all three phases can coexist. Water reaches its triple point at just above freezing (0.01° C) and at a pressure of 0.006 atm.
For water, the triple point is reached at a temperature of 0.01°C and a pressure of 611.657 pascals. Under these very specific conditions, ice, liquid water, and water vapor coexist in equilibrium. At the triple point, the energy input and output balance is such that water molecules have the freedom to transition between phases. When energy is added, some molecules gain enough energy to become gas, hence boiling. Conversely, when energy is lost, some molecules slow down enough to form a solid, thus freezing.
The triple point of water occurs at a temperature of 0.01 °C and a pressure of 0.00603659 atm... At this intersection of temperature and pressure, water molecules exhibit a unique equilibrium where they exist simultaneously as solid ice, liquid water, and water vapor.
The triple point is the specific temperature and pressure at which solid, liquid, and gas phases of a substance coexist in equilibrium. At this exact point: A substance can melt, freeze, boil, condense, sublime, and deposit. All phase changes occur simultaneously.
The triple point of water is a fundamental concept in thermodynamics, defined at 273.16 K (0.01°C) and 611.657 Pa, where all three phases coexist. This is the basis for the kelvin scale and confirms that boiling (liquid to gas) and freezing (liquid to solid) can occur simultaneously in equilibrium.
Triple point of water: Temperature: 273.16 Kelvin (0.01 degree celsius), Pressure: 611 pascal (4.58 mm of Hg). Triple point of a substance is defined as a point in a phase diagram at which all three states of the substance coexist.
the triple point of water is reached when the temperature is 273.16 kelvins (or 0.01 °C) and the pressure is at 0.006 atmospheres... creating ideal conditions for a substance to exist in all three phases.
The triple point of a substance is the temperature and pressure at which three phases (gas, liquid, and solid) of that substance may coexist in thermodynamic equilibrium.
Did you know water can boil and freeze at the exact same time? It's called the triple point, and it's real science!
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Expert review
How each expert evaluated the evidence and arguments
Expert 1 — The Logic Examiner
Multiple sources establish that at the triple point (≈0.01 °C, ≈611 Pa) water can have solid, liquid, and vapor coexist in equilibrium (e.g., NIST in Source 1; Khan Academy in Source 7), and one source explicitly states that at this low pressure pure water both boils and freezes at 0.01 °C (Source 6), which logically entails that the liquid–gas and liquid–solid phase-change conditions are simultaneously satisfied under those pressure conditions. The opponent's objection hinges on redefining “boil/freeze” as requiring macroscopic net phase conversion rather than equilibrium two-way transitions, but the claim as written (“can…under specific pressure conditions”) is satisfied by triple-point coexistence and the evidence supports it, so the claim is true though casual readings may over-imagine a dramatic, sustained simultaneous bulk boiling-and-freezing process.
Expert 2 — The Context Analyst
The claim is technically accurate but omits critical framing context: the "specific pressure conditions" are extremely narrow (611 Pa, roughly 0.6% of atmospheric pressure) and the phenomenon is better described as thermodynamic equilibrium coexistence of three phases rather than the colloquial sense of "boiling and freezing" as vigorous, active, simultaneous processes. Sources 1, 3, 6, and 7 confirm the triple point is real and well-established, but the opponent correctly notes (supported by Source 9's lab demo) that in practice the phase transitions can appear sequential rather than truly simultaneous, and the everyday connotations of "boil" and "freeze" imply energetic, dynamic processes rather than equilibrium coexistence. However, Source 6 (UNSW) explicitly states that at 611 Pa water both boils and freezes at 0.01°C, and Sources 11 and 13 confirm that all phase transitions — including boiling and freezing — can occur simultaneously at the triple point; the claim's core assertion is scientifically defensible and supported by authoritative sources (NIST, UNSW, Khan Academy), with the main omission being that this requires an extraordinarily specific and non-ambient pressure condition and that "simultaneously" refers to thermodynamic equilibrium rather than the dramatic visual of concurrent vigorous boiling and freezing.
Expert 3 — The Source Auditor
The most authoritative source in this pool — Source 1 (NIST, authority score 1.0, dated 2025) — explicitly confirms that the triple point of water is "the condition in which water exists simultaneously in solid, liquid, and gaseous states," and Source 2 (PMC/PubMed Central, authority score 0.95) provides peer-reviewed experimental verification of triple point conditions. Source 6 (University of New South Wales, authority score 0.75) directly states that at 611 Pa and 0.01°C, "pure water boils at 0.01°C, and it also freezes at 0.01°C," confirming that both phase transitions share the same pressure-temperature coordinate. The opponent's argument that the triple point is merely "static coexistence" rather than simultaneous active phase transitions is a philosophical distinction that does not undermine the claim's core truth: under specific pressure conditions (~611 Pa), water's boiling point and freezing point converge to the same temperature, meaning both processes can and do occur simultaneously — a fact confirmed by the highest-authority sources (NIST, PMC) and corroborated by multiple independent academic sources (UNSW, nuclear-power.com, Khan Academy). The claim is therefore well-supported by the most reliable evidence, with the minor caveat that "simultaneously boil and freeze" is a colloquial but scientifically defensible description of triple-point coexistence.
Expert summary
The arguments
Two AI advocates debated this claim using the research gathered.
Argument for
The claim is true because at water's triple point—a specific low-pressure condition—solid, liquid, and vapor coexist in thermodynamic equilibrium, meaning freezing (liquid→solid) and boiling (liquid→gas) can occur simultaneously (Source 1, National Institute of Standards and Technology (NIST); Source 7, Khan Academy). Multiple independent references quantify these conditions at about 0.01 °C and ~611 Pa and explicitly note that at this pressure water both boils and freezes at the same temperature, directly matching “simultaneously boil and freeze under specific pressure conditions” (Source 6, University of New South Wales Physics Animations; Source 3, nuclear-power.com).
Your argument conflates coexistence of phases with simultaneous active phase transitions — Source 1 (NIST) and Source 3 (nuclear-power.com) describe a static thermodynamic equilibrium where all three phases are merely present together, not a dynamic process where boiling and freezing are actively and concurrently occurring. Furthermore, your reliance on Source 6 (University of New South Wales) actually undermines your case, as it states water "boils at 0.01°C" and "freezes at 0.01°C" as separate threshold conditions at that pressure — not as a description of both processes happening in the same moment — and Source 9's own lab demonstration confirms the sequential reality: pressure drops, water boils first, then the remaining liquid freezes afterward, exposing your "simultaneously" framing as a logical leap unsupported by the evidence.
Argument against
The claim that water can "simultaneously boil and freeze" is a misleading oversimplification of what actually occurs at the triple point: as Sources 1, 3, and 7 confirm, the triple point is a precise thermodynamic equilibrium where solid, liquid, and gas coexist — not a dynamic process where boiling and freezing actively occur at the same time, but a static balance where all three phases are merely present together. Furthermore, Source 9's own description reveals the sequential, not simultaneous, nature of the phenomenon — the water first boils due to pressure reduction, and only then does the remaining liquid freeze from heat loss — demonstrating that "boiling and freezing at the same time" is a dramatic narrative gloss, not a scientifically accurate description of the triple point equilibrium defined by Sources 1, 3, and 8.
You're creating a false dichotomy between “equilibrium coexistence” and “active phase change”: at the triple point, coexistence in thermodynamic equilibrium (Source 1, National Institute of Standards and Technology (NIST); Source 7, Khan Academy) precisely means the liquid–gas and liquid–solid boundaries are simultaneously satisfied, so boiling and freezing can occur concurrently at the same (P,T), not merely “sit there” as inert phases. And your appeal to “sequential” storytelling cherry-picks Source 9's demo narrative while ignoring that authoritative explanations explicitly state that at ~611 Pa and 0.01 °C pure water both boils and freezes (Source 6, University of New South Wales Physics Animations), which directly matches the motion's “simultaneously…under specific pressure conditions.”