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Absolute zero is the lowest limit of the thermodynamic temperature scale; a state at which the enthalpy and entropy of a cooled ideal gas reach their minimum value. The fundamental particles of nature have minimum vibrational motion, retaining only quantum mechanical, zero-point energy -induced particle motion.
At absolute zero (zero kelvins) the system must be in a state with the minimum possible energy. Entropy is related to the number of accessible microstates, and there is typically one unique state (called the ground state) with minimum energy. [1] In such a case, the entropy at absolute zero will be exactly zero.
Experimentally, absolute zero can be approached only very closely; it can never be reached (the lowest temperature attained by experiment is 38 pK or 38 trillionths of a Kelvin). [4] Theoretically, in a body at a temperature of absolute zero, all classical motion of its particles has ceased and they are at complete rest in this classical sense.
a) Single possible configuration for a system at absolute zero, i.e., only one microstate is accessible. b) At temperatures greater than absolute zero, multiple microstates are accessible due to atomic vibration (exaggerated in the figure). At absolute zero temperature, the system is in the state with the minimum thermal energy, the ground state.
Colloquially, the Kelvin temperature scale, where absolute zero is the temperature at which molecular energy is at a minimum, and the Rankine temperature scale are also referred to as absolute scales. In that case, an absolute scale is a system of measurement that begins at a minimum, or zero point, and progresses in only one direction. [4]
In 1908 he managed to lower the temperature to less than −269 °C (−452.2 F, 4 K), which is four degrees above absolute zero. Only in this exceptionally cold state will helium liquefy; the boiling point of helium being at −268.94 °C (−452.092 F). Kamerlingh Onnes received a Nobel Prize for his achievement. [9]
To obtain the absolute value, we need the third law of thermodynamics, which states that S = 0 at absolute zero for perfect crystals. For any irreversible process, since entropy is a state function, we can always connect the initial and terminal states with an imaginary reversible process and integrating on that path to calculate the difference ...
In 1954, with absolute zero having been experimentally determined to be about −273.15 °C per the definition of °C then in use, Resolution 3 of the 10th General Conference on Weights and Measures (CGPM) introduced a new internationally standardized Kelvin scale which defined the triple point as exactly 273.15 + 0.01 = 273.16 degrees Kelvin.