Definition and Concept of Absolute Zero
– Absolute zero is the lowest limit of the thermodynamic temperature scale, defined as zero kelvin (-273.15°C).
– Absolute zero is commonly considered the lowest temperature possible.
– Matter at absolute zero is in its ground state, with the lowest internal energy.
– Thermodynamics laws indicate that absolute zero cannot be reached using only thermodynamic means.
– Even at absolute zero, a system would still possess quantum mechanical zero-point energy.
Departure from Ideal Gas Behavior
– Real substances deviate from ideal gas behavior as they approach the change of state to liquid and solid.
– The enthalpy of vaporization and enthalpy of fusion exceed the ideal gas change in enthalpy to absolute zero.
Thermodynamics near Absolute Zero
– At temperatures near 0K, molecular motion ceases and entropy approaches zero.
– The entropy change for any isothermal process approaches zero as temperature approaches absolute zero.
– A perfect crystal has no structural imperfections and its entropy approaches a constant value.
– Adiabats, represented as curves on a graph, have constant entropy.
– No adiabatic process initiated at a nonzero temperature can lead to zero temperature.
History and Discoveries
– Robert Boyle, Guillaume Amontons, and Johann Heinrich Lambert discussed the concept of absolute zero in the 18th century.
– Lord Kelvin devised a scale of absolute temperature independent of any substance, placing the zero at -273°C.
– The value of -273°C was not immediately accepted and different values were used in the early 20th century.
– Heike Kamerlingh Onnes won the Nobel Prize for his work on low-temperature physics, including the discovery of superconductivity near absolute zero.
– Cryogenics and the development of dilution refrigerators have advanced our understanding of absolute zero.
Applications and Extreme Cold in the Universe
– Scientists have worked to obtain even lower temperatures to study phenomena like superconductivity.
– The Boomerang Nebula is considered the coldest region in the universe, with a temperature of about 1 Kelvin.
– The Cold Atom Laboratory on the International Space Station has created ultracold atoms reaching temperatures colder than absolute zero.
– Sedna, a dwarf planet in our solar system, has a surface temperature estimated to be below 33 Kelvin.
– The study of extreme cold temperatures in the universe helps us understand its fundamental properties. Source: https://en.wikipedia.org/wiki/Absolute_zero
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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, taken as zero kelvin. The fundamental particles of nature have minimum vibrational motion, retaining only quantum mechanical, zero-point energy-induced particle motion. The theoretical temperature is determined by extrapolating the ideal gas law; by international agreement, absolute zero is taken as −273.15 degrees on the Celsius scale (International System of Units), which equals −459.67 degrees on the Fahrenheit scale (United States customary units or imperial units). The corresponding Kelvin and Rankine temperature scales set their zero points at absolute zero by definition.
It is commonly thought of as the lowest temperature possible, but it is not the lowest enthalpy state possible, because all real substances begin to depart from the ideal gas when cooled as they approach the change of state to liquid, and then to solid; and 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. In the quantum-mechanical description, matter at absolute zero is in its ground state, the point of lowest internal energy.
The laws of thermodynamics indicate that absolute zero cannot be reached using only thermodynamic means, because the temperature of the substance being cooled approaches the temperature of the cooling agent asymptotically. Even a system at absolute zero, if it could somehow be achieved, would still possess quantum mechanical zero-point energy, the energy of its ground state at absolute zero; the kinetic energy of the ground state cannot be removed.
Scientists and technologists routinely achieve temperatures close to absolute zero, where matter exhibits quantum effects such as Bose–Einstein condensate, superconductivity and superfluidity.
