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Gap between indoor and outdoor temperatures

 
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Please be careful about the temperature difference between indoors and outdoors.
 

You can spend light clothes in the room, but when you go outside, you can see the cold north wind.I hurriedly returned to get the stall.At once ... → Continue reading

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temperature

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temperature(Oh,English: temperature) Is an index showing the degree of heating and cooling. The high and low temperatures of the two objectsThermal contact[Question](thermal [1]contact)エ ネ ル ギ ーIs defined by the direction in which it moves.That is, it can be said that temperature is an index indicating the direction in which energy moves naturally.Standardly, the temperature on the side where energy flows out due to contact is high, and the temperature on the side where energy flows in is low.If no energy transfer occurs when they are brought into contact, the temperatures of the two objects are equal.This state is called temperature equilibrium (thermal equilibrium).

Maxwell says that the temperature of the gas is分子It depends only on the mean value of the random translational kinetic energy of. However, he said that similar results for objects in the liquid or solid state have not yet been established.[XNUMX].. Recently, Igarashi has proposed a definition of temperature that holds for liquids and solids. According to it, if the intermolecular force is a function of only position, even if there is interaction in polyatomic molecule, the average value of translational kinetic energy of the molecule can be exactly obtained by using statistical mechanics. , The result is equivalent to Maxwell's velocity distribution law and is a function only of absolute temperature and mass[XNUMX], [XNUMX].. The following is a brief description of this result. It can be said that "temperature represents an average value of random translational kinetic energies of atoms and molecules." Dr. Harashima's text says that Maxwell's velocity distribution law for the velocity distribution of translational motion of gas molecules holds for not only gases but also liquids and solids.[5], But no mathematical proof is attached. Igarashi uses a thought experiment that the temperature is determined by the average value of the kinetic energy of the disorderly translational motion of the molecule, and rotational and vibrational motions in the molecule Have proved[6], [7].

Statistical mechanicsAccording tomaterialCompose分子Messy translational movement ofエ ネ ル ギ ーThe average value of can be obtained as Igarashi derived. The temperature thus determined matches the thermodynamic temperature.

Thermodynamic temperature OfZero point(0Kelvin) Isabsolute temperatureIt is called a state where the disordered translational motion of molecules is stopped. However, absolute zero is an extreme state, and a finite operation does not cause matter to reach absolute zero. Also,Quantum mechanicalIUncertaintyTherefore, the movement of the molecule does not stop even if it reaches absolute zero. However, the molecular motion at this time is not a random translational motion. The motion of the molecule at this time is called quantum mechanical zero-point oscillation (zero-point motion), and since it is not a random motion, it does not contribute to entropy.Therefore, the entropy is zero at absolute zero, and the molecular random The translational motion also stops and becomes zero. The temperature ismaterialCompose分子Messy translational movement ofAverage value of energyThat's why.

The temperature isChemical reactionHave a strong influence on. Also,Biology Each has its own, and can only survive in an environment with a very narrow temperature range.Chemical,BiologyInObservation,ExperimentThen, it is necessary to record the temperature as a basic condition, or adjusting the temperature is an important condition for establishing the experiment. Also, in biology and medicine, tissues and samplesRefrigeratedDoing so has the meaning of reducing the rate of chemical change by lowering the temperature.

Kinetic theory approach

In kinetic theory, Kelvin temperature is related to the average value of kinetic energy per atom and one degree of freedom in temperature (thermal) equilibrium state.

Energy distribution lawAccording to (equipartition theorem), the kinetic energy per individual degree of freedom of the system is kBT/2 Becomes here, T Is the absolute temperature, kB Is the Boltzmann constant. In three-dimensional space, the translational degree of freedom of particles is 3, so monatomic gas particles are3kBT/2 Have the energy to become.

For example, gas oxygen molecules (O2) Has rotation (2 degrees of freedom) and vibration (1 degree of freedom) in addition to translation. The kinetic energy for each degree of freedom is kBT/2 However, the vibration mode is frozen quantum mechanically in the low temperature region including normal temperature, so the total energy per molecule is 5kBT/2 Becomes Also, in the high temperature region, it becomes a mode of vibration similar to a harmonic oscillator, and kinetic energy and potential energy almost equal to it are added, so the total energy per molecule is 7kBT/2 Becomes Each mode such as translation, rotation, and vibration is equally distributed under such a fixed constraint, and its unified measure (such as groundwater level) can be called temperature, but from the viewpoint of potential and periodicity, it is the most constrained. It is the translational energy of the gas that has less.

The temperature energy of a solid isDebye temperaturePer atom in the higher temperature range, 6kBT/2 Is approximated by (Duron-Petit's law), this is also because one of the atoms constitutes a harmonic oscillator with three degrees of freedom.

The law of equal distribution of energy is not only valid for different kinds of gas particles in a mixed gas, but this is a result, and in fact, it is considered that there is an equalizing action that approaches this result. It can be said that the effect of this equalizing action on spatial nonuniformity in the object is heat conduction, but even if they occupy the same space, it is possible that the substance and the radiation field hold different temperatures for a long time. , In this case, each temperature should be considered separately (radiation temperature may not be commonly defined in the first place).

Since temperature is a statistical entity, it requires a rather wide measurement range spatially and temporally, and in the case of gas, it requires time and space in which its particles collide multiple times. For example, modes of motion such as translation, rotation, and vibration of gas are considered to be sufficiently equalized (under the above-mentioned constraint) in such a space-time range. However, as Maxwell points out, the modes of motion such as molecular rotation and vibration are excited depending on the temperature, but it must be noted that they do not contribute to the temperature.[XNUMX].. So-called "adiabatic free expansion" is an exceptional transient phenomenon.

Definition of temperature

Although there were various definitions of temperature in history,International quantity systemInBasic quantityLocated inThermodynamic temperatureIs defined as temperature (heat)EquilibriumInternal energy of the system atU, Keeping the volume constantEntropy SIt is partially differentiated with.

(T= ∂ U/ ∂ S)v.. At present, the definition of temperature and entropy in the non-equilibrium state is in the process of development, as it may not be possible to define it in its original meaning.

Temperature is one of the hard to measure physical quantities. This is a statistical value, and when the number of molecules is small, such as when the density is low or in a very narrow range, the value is statistically unstable and meaningless. Observing each one is not possible with the current technology, and it is because indirect measurement is performed instead.

The temperature can be measured by measuring the electromagnetic waves radiated from the object to be measured, or by taking a long time to bring the measurement probe into contact with the object to be measured to bring it into a temperature (thermal) equilibrium state. There is a way to measure. Both methods have some measurement problems. However, recent high-speed temperature measuring devices have been able to measure objects with a size of several tens of micrometers and a measurement time of several milliseconds, and their effectiveness as one means of capturing physical phenomena has improved. There is.

History of temperature and thermometer

Although there is a myth that the first attempt to quantitatively express the degree of warmth and warmth of an object was made,Galileo GalileiIs believed to be. Galilei is airThermal expansionA device that can measure the temperature of an object using the property ofthermometerIt was created. Since the thermometer made by Galilei was affected by atmospheric pressure and so on, it was not enough to express the temperature quantitatively, but using the change in the property of the substance depending on the temperature in this way, the degree of cold and warm Attempts to quantitatively express the equation continued. The first time I tried to express temperature numerically with a graduated thermometerOle reamerIs. Roemer created a temperature scale where the boiling point of water was 60 degrees and the melting point of water was 7.5 degrees. To create the temperature scale, two defined fixed points are required in this way. Many unique temperature scales were created, but nowadaysAndels CelsiusCreated byCelsiusTemperature scale,Gabriel FahrenheitCreated byFahrenheitThe temperature scale is mainly used.

Once with temperatureheatThe distinction between the concepts was not made clear. The first time I noticed the difference between temperature and heatJoseph BlackIs believed to be. Black has iceMeltingIt was discovered that the temperature does not change even if it absorbs heat while doing (latent heat). We also conducted an experiment in which mercury and water of the same mass at different temperatures were mixed, and we found that the amount of water and mercury changed by a constant was always the same. this isHeat capacityThe constant multiplied by the temperature change corresponds to the heat capacity, and the amount that is always equal is the amount of heat that moves. These experiments established that temperature and heat are different concepts.

Then, in the 19th century, the construction of thermodynamics proceeded due to the demand for the development of efficient heat engines.Nicolas Leonard Sadie CarnotFound that the efficiency of a heat engine has an upper limit determined by the temperature difference between the heat source and the refrigerant. From thisSecond law of thermodynamicsThe research on According to the second law of thermodynamics, from the outsideworkUnless is done, heat energy will only transfer from a hot object to a cool object.

William Thomson TheCarnot cycleIt was shown that the temperature scale can be constructed from the heat energy flowing in and out of the heat source and the refrigerant. thisThermodynamic temperatureIt is called a scale. At thermodynamic temperature, one defined fixed point is the temperature at which the efficiency of the Carnot cycle is 1, which is -1°C on the Celsius scale. According to the second law of thermodynamics, infinite work is required to reach this temperature, and there is no lower temperature. Therefore, this temperatureabsolute temperatureAlso called. On the thermodynamic temperature scale, this absolute zero is the origin (0 K). The existence of the lower limit of temperature was before ThomsonCharles' LawTherefore, it was considered as the temperature at which the volume of any gas becomes zero.

Regarding the meaning of temperature at the atomic and molecular level,James Clark MaxwellIt became clear for the first time by the kinetic theory of gas molecules. The velocity distribution of the translational motion of gas molecules isMaxwell distributionTherefore, the shape of this distribution function istemperatureDepends on. Especially, the average value of translational kinetic energy of gas molecule is 3/2 kT(K:Boltzmann constant, T: thermodynamic temperature), which is proportional to temperature. That is, temperature is also a numerical value that represents the intensity of translational motion of molecules. For this reasonplasmaThe average kinetic energy of ions and electrons inside may be expressed as temperature (plasmaThis is because the ions and electrons inside have only translational degrees of freedom). At this time, it is usually expressed by the temperature T such that the average kinetic energy = kT.

Ludwig BoltzmannDeveloped this Maxwell ideaStatistical thermodynamicsWas built. Statistical thermodynamics extends this idea to all forms of energy. The higher the temperature, the larger the proportion of atoms and molecules having high energy, and the larger the average energy of atoms and molecules. Thus in statistical thermodynamics temperature is分子Is an index showing the manner of translational kinetic energy distribution of.

Quantum theoryOnce established, classical statistical thermodynamicsQuantum statisticsIt became clear that it was an approximation of. In classical theory, every particle at 0 K has the lowest energy state in which it has stopped moving, but in quantum theory, a particle has zero energy even at 0 K and is not in a stationary state. thisPhysical phenomenon TheZero point vibrationIt is called. Also,Bose particleThe energy distribution ofBose Einstein distribution,FermionsThe energy distribution ofFermi-Dirac distributionBecomes In fermions,Pauli exclusion principleTherefore, there is a particle with a large energy that corresponds to tens of thousands of K in classical theory even at absolute zero, but this is due to the fact that energy is regarded as temperature by substituting it in kT. And it doesn't mean the temperature of Makoto. It is important to keep in mind that the temperature分子It is the same as the classical statistics in that it is an index of the translational kinetic energy distribution of.

Temperature units and types

Temperature unit comparison
KelvinCelsius degreeFahrenheit degreeRankin degreeDreel degreeNewton degreeRheomure degreeRömer degree
absolute temperature0−273.15−459.670559.725−90.14−218.52−135.90
地球Minimum of surfacetemperature(※ 1)183.95−89.2−128.56331.11283.8−29.436−71.36−39.33
Fahrenheit OfFreezer255.37−17.780459.67176.67−5.87−14.22−1.83
Wed OfMelting point(Standard conditionunder)273.15032491.67150007.5
Average temperature on the surface of the earth2881559518.67127.54.951215.375
A humanAverage ofbody temperature309.9536.898.24557.9194.812.14429.4426.82
Maximum temperature on the earth's surface (*2)329.8556.7134.06593.7364.9518.71145.3637.268
WaterBoiling point(Under standard conditions)373.15100212671.670338060
TitaniumMelting point of1941166830343494−23525501334883
(I.e.Surface temperature58005526998010440−8140182344212909

International temperature scale (ITS-90)

International unit systemIn, the thermodynamic temperature is used for the temperature, and Kelvin is to be used as the unit. However, thermodynamic temperature is a temperature defined from the idealized system properties, so it is not easy to actually measure it. Therefore, as a temperature that is practically consistent with the thermodynamic temperature and is easy to measure,International temperature scale(Kokusai Ondo Mori, ITS, International Temperature Scale) is defined. The temperature scale currently in use was set in 1990.ITS-90It is called. The International Temperature Scale consists of a measuring instrument that defines the temperature of an area and a fixed point for calibrating it.[1].

Definition method

Definition fixed point

  • heliumVapor pressure point of: values ​​at 3 K-5 K used for calibration
  • Equilibrium hydrogen (Ortho hydrogen and para hydrogenIs in equilibrium)Three points: 13.8033 K
  • Equilibrium hydrogen vapor pressure points: Values ​​of 17.025 K-17.045 K and 20.26 K-20.28 K are defined.
  • Helium gas thermometer readings: 16.9 K-17.1 K and 20.2 K-20.4 K values ​​used for calibration
  • ネ オ ンTriple point: 24.5561 K
  • oxygenTriple point: 54.3584 K
  • ArgonTriple point: 83.8058 K
  • mercuryTriple point: 234.3156 K
  • Triple point of water: 273.16 K (another defined fixed point on the thermodynamic temperature scale)
  • galliumMelting point under standard atmospheric pressure (101 325 Pa): 302.9146 K
  • indiumFreezing point under standard atmospheric pressure: 429.7485 K
  • TinFreezing point under standard atmospheric pressure: 505.078 Kᐸ
  • zincFreezing point under standard atmospheric pressure: 692.677 K
  • aluminumFreezing point under standard atmospheric pressure: 933.473 K
  • SilverFreezing point under standard atmospheric pressure: 1234.93 K
  • FriFreezing point under standard atmospheric pressure: 1337.33 K
  • copperFreezing point under standard atmospheric pressure: 1357.77 K

Temperature measurement method

There are two types of measuring methods: the contact type, which measures directly by touching an object, and the non-contact type, which measures without touching.

The contact type includes expansion type, electric type, counting type, etc. The expansion type measures the pressure change of gas due to temperature change such as or, measures the length of liquid such as, and measures the deformation of solid.bimetalThere is a formula. The electric type uses the principle that the resistivity changes with temperature.thermocoupleSuch as using metal wire,Thermistor,diodeな どsemiconductorSome use. The method that can measure temperature changes as resonance frequency changes is classified as a counting type.liquid crystalCan also be contacted to measure temperature changes.

The non-contact type is divided into two types depending on the detection wavelength. One is the short wavelength of about 2µm-2µm.InfraredQuantum type with detection wavelength band. The other is for long wavelengths of about 8-14 μm.InfraredThermal type with the detection wavelength band. Each detection wavelength band depends on the atmosphereInfraredIn the wavelength band with a small attenuation of the quantum type, the quantum type uses InSb (), InAs (Indium arsenide) Etc., the thermal typeMicrobolometerI am using. As a typical non-contact type thermometer,InfraredThermographyThere is.

Sensible temperature

Human capitalThe temperature you feel is not decided only by the temperature,Wind,(I.e., Of surrounding objectsHeat radiationIs also affected. Taking these into consideration, the temperature expressed quantitativelySensible temperatureThat.

Temperature difference

Temperature difference(Hondosa) is literally twomaterialOf the temperature difference inthe amount OfdifferenceIn Although, 1990Since the early days[Source required]JapanThen, the difference in enthusiasm, way of thinking and speculation among multiple parties for one thing or project,ValuesOf the differenceMetaphorIs sometimes expressed as "temperature difference".[2] This is a word that regards the thoughts and thoughts of each person concerned as hot and cold thoughts and compares the difference as the difference in physical temperature.

footnote

[How to use footnotes]
  1. ^ Institute of Metrology "1990 International Temperature Scale (ITS-90)" (Japanese translation) October 1991 (PDF)
  2. ^ Temperature difference,SanseidoDaily new word dictionary

References 

  1. PCRiedi, "Thermal Physics An introduction to thermodynamics, statistical mechanics, and kinetic theory" 2nd Edition, Oxford University Press p.9, 2.1 First law of thermodynamics XNUMX Zeroth law and scale of temperature has the following description. There is an explanation saying "The most directly accessible thermal concept is not heat but rather temperature, the relative sensation of hot and cold." The terms thermo and thermal are transliterated terms from Greece and are used to mean "in everyday life," "heat," "in temperature," etc. In Western European physics, they are used in distinction from heat. It is used in the sense of temeperature. The reason is that heat has a meaning attached to it, which means that it is used to wipe away it. It is important to keep in mind that thermal is used to mean "temperature," not "heat," as introduced in the explanation of PCRiedi above. In Japan, I was not aware of this, I could not translate the terms thermo and thermal well, and I translated it as "heat". Therefore,The correct translation of thermal should be "temperature" or "thermal". In Japan, the distinction between “heat” and “temperature” is still ambiguous, and the current situation is that the beginners are confused. I think it's better to correct mistakes in terms as in Western Europe[Original research?].
  2. JC Maxwell World Famous Book 65 Contemporary Science I, Hideki Yukawa, Ken Inoue, Responsible Editor, Commentary, "Outline of Recent Molecular Science Focusing on Molecular Theory of Gas", pp1231-9, Original The Scientific Papers of James Clerk Maxwell Vol.2 (1965) Dover, pp.445-484
  3. Yasunori Igarashi "ᐸ(1/2)mvtr2ᐳ = (3/2)kT Does the relational expression of hold for liquids and solids? -From a consideration of the principle of temperature measurement-Proceedings of the Physical Society of Japan vol.69, No.2, p.240 (2014.9)
  4. Yasunori Igarashi "Velocity distribution in interacting polyatomic molecular groups-Molecular meaning of temperature" Vol.72, No.1, DVD version, Chemical Physics Subcommittee (017.3)
  5. Akira Harashima Basic Physics I Mechanics / Relativity / Thermal Science Academic Books 309 First Edition pp.310-XNUMX 
  6. Yasunori Igarashi "What is temperature?-The molecular meaning of temperature-" Proceedings of the Physical Society of Japan vol.66, No.1, p.443(2011.3)
  7. Yasunori Igarashi "Molecular Theoretical Structure of Temperature Concept and Verification Experiments" Proc.

 

 

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