Absolute zero is the lowest possible limit of the thermodynamic temperature scale, at which point the enthalpy and entropy of a cooled ideal gas reach their minimum value, which is referred to as zero kelvin. The fundamental particles of nature state that everything in nature has minimum vibrational motion. The theoretical temperature is determined by making use of the ideal gas law., and by international agreement, this temperature is considered -273.15 degrees on the Celsius scale which translates to −459.67 degrees on the Fahrenheit scale. The corresponding Kelvin and Rankine temperature scales set their zero points at absolute zero by definition.
It is commonly considered the lowest temperature possible, but it is not the lowest enthalpy state possible, since all real substances start to depart from the ideal gas. When cooled to such low temperatures they approach the change of state to liquid, and then to solid. The sum of the enthalpy of vaporization (gas to liquid) and enthalpy of fusion (liquid to solid) exceeds the ideal gas’s change in enthalpy to absolute zero. The laws of thermodynamics state that this temperature cannot be achieved by using just thermodynamic means since the temperature of the substance that is being cooled approaches the temperature of the cooling agent asymptotically, and a system at absolute zero still requires quantum mechanical zero-point energy, the energy of its ground state at absolute zero. The kinetic energy of the ground state is not possible to be reached. Scientists routinely achieve temperatures that are close to absolute zero, where matter exhibits extreme quantum effects such as superconductivity, superfluidity, and Bose-Einstein condensate.
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