absolute zero (redirected from -273 C)

absolute zero, the zero point of the ideal gas temperature scale, denoted by 0 degrees on the Kelvin and Rankine temperature scales, which is equivalent to −273.15°C; and −459.67°F;. For most gases there is a linear relationship between temperature and pressure (see gas laws), i.e., gases contract indefinitely as the temperature is decreased. Theoretically, at absolute zero the volume of an ideal gas would be zero and all molecular motion would cease. In actuality, all gases condense to solids or liquids well above this point. Although absolute zero cannot be reached, temperatures within a few billionths of a degree above absolute zero have been achieved in the laboratory. At such low temperatures, gases assume nontraditional states, the Bose-Einstein and fermionic condensates. See also low-temperature physics; temperature.

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absolute zero

Temperature at which a thermodynamic system (see thermodynamics) has the lowest energy, 0 kelvin (K). It corresponds to −459.67°F (−273.15°C) and is the lowest possible temperature theoretically achievable by a system. A gas at constant pressure contracts as the temperature is decreased. A perfect gas would reach zero volume at absolute zero. However, a real gas condenses to a liquid or a solid at a temperature higher than absolute zero. At absolute zero, the system's molecular energy is minimal and none is available for transfer to other systems. The Kelvin temperature scale has absolute zero as its zero point, and its fundamental unit is the kelvin.

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absolute zero

The temperature at which molecular activity is at a minimum. Absolute zero is -273.15 degrees Celsius and -459.67 degrees Fahrenheit. See Kelvin.

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absolute zero

the lowest temperature theoretically attainable, at which the particles constituting matter would be in the lowest energy states available; the zero of thermodynamic temperature; zero on the International Practical Scale of Temperature: equivalent to --273.15°C or --459.67°F

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absolute zero [′ab·sə‚lüt ′zir·ō]

(thermodynamics)

The temperature of -273.16°C, or -459.69°F, or 0 K, thought to be the temperature at which molecular motion vanishes and a body would have no heat energy.

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Absolute zero

The temperature at which an ideal gas would exert no pressure. The Kelvin scale of temperatures is defined in terms of the triple point of water, T₃ = 273.16° (where the solid, liquid, and vapor phases coexist), and absolute zero. Temperature is measured most simply via the constant-volume ideal-gas thermometer, in which a small amount of gas is introduced (in order to limit the effect of interactions between molecules) and then sealed off, and the gas pressure P referenced to its value at the triple point P(T₃) is measured. The ideal-gas law applies if the molecules in a gas exert no forces on one another and if they are not attracted to the walls. Absolute zero is the temperature at which the pressure of a truly ideal gas would vanish. See Temperature measurement

According to classical physics, all motion would cease at absolute zero; however, the quantum-mechanical uncertainty principle requires that there be a small amount of residual motion (zero-point motion) even at absolute zero. See Kinetic theory of matter, Uncertainty principle

Temperature can also be defined from the Boltzmann distribution. If a collection of spin-1/2 magnetic ions is placed in a magnetic field, the ratio of the occupancy of the lower to the higher energy state is given by the equation below.

Here k is Boltzmann's constant, ΔE is the magnitude of the difference in energy between the states, and T is the Kelvin temperature. Thus, at high temperatures the two states have nearly equal occupation probability, while the lower energy state is progressively favored at lower temperatures. At absolute zero, only the lower energy level is occupied. This relation allows for the possibility of negative temperatures when the population of the higher energy state exceeds that of the lower state. See Boltzmann constant, Boltzmann statistics

Negative temperatures notwithstanding, the third law of thermodynamics states that the absolute zero of temperature cannot be attained by any finite number of steps. The lowest (and hottest) temperatures that have been achieved are on the order of a picokelvin (10^-12K). These are spin temperatures of nuclei which are out of equilibrium with the lattice vibrations and electrons of a solid. The lowest temperatures to which the electrons have been cooled are on the order of 10 microkelvins in metallic systems. See Low-temperature physics, Temperature