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Liquid helium is a physical state of helium at very low temperatures at standard atmospheric pressures. Liquid helium may show superfluidity . At standard pressure, the chemical element helium exists in a liquid form only at the extremely low temperature of −269 °C (−452.20 °F; 4.15 K).
2 He helium; use: 0.0829 ... Values refer to the enthalpy change in the conversion of liquid to gas at the boiling point ... "Corrected Values for Boiling Points and ...
This is a list of the various reported boiling points for the elements, with recommended values to be used elsewhere on Wikipedia. ... 2 He helium; use: 4.222 K: − ...
The entropy of vaporization of XeF 6 at its boiling point has the extraordinarily high value of 136.9 J/(K·mol). [4] The characteristic of those liquids to which Trouton’s rule cannot be applied is their special interaction between molecules, such as hydrogen bonding. The entropy of vaporization of water and ethanol shows positive deviance ...
Boca Raton, Florida, 2003; Section 6, Fluid Properties; Critical Constants. Also agrees with Celsius values from Section 4: Properties of the Elements and Inorganic Compounds, Melting, Boiling, Triple, and Critical Point Temperatures of the Elements Estimated accuracy for Tc and Pc is indicated by the number of digits.
2 He helium-4; Hoffer et al. 0.19085 ... (He-I at boiling point: 4.222 K) ... The suggested values for liquid densities refer to "at the melting point (m.p.)" by default.
Liquid helium-4 can be cooled to about 1 K (−272.15 °C; −457.87 °F) using evaporative cooling in a 1-K pot. Similar cooling of helium-3, which has a lower boiling point, can achieve about 0.2 kelvin in a helium-3 refrigerator. Equal mixtures of liquid 3 He and 4
A liquid may be converted to a gas by heating at constant pressure to the boiling point, or else by reducing the pressure at constant temperature. At temperatures below its critical temperature , a gas is also called a vapor , and can be liquefied by compression alone without cooling.