Name: kelvin temperature and gas thermometer standards
Uploaded: 2023-04-30T12:29:16.000Z
Duration: 1 min 22 s
Channel: JoVE

K12 Standards

Texas Essential Knowledge and Skills

High School

Chemistry

CHEM.13

CHEM.13.D

Gas Thermometers and the Kelvin Scale

Termometr gazowy ocenia temperaturę na podstawie zmian ciśnienia lub objętości wypełnionego gazem.
Istnieją dwa rodzaje termometrów gazowych: stałoobjętościowe i stałociśnieniowe, przy czym najczęściej stosowany jest termometr gazowy o stałej objętości.
Zasada działania tego termometru polega na tym, że przy stałej objętości ciśnienie gazu wzrasta wraz ze wzrostem temperatury.
Aby skalibrować termometr gazowy, mierzy się ciśnienie w temperaturze 0 i 100 stopni Celsjusza.
Wartości te są wykreślane w linii prostej, która jest ekstrapolowana w celu znalezienia temperatury zerowego ciśnienia.
Ta temperatura jest punktem zerowym skali Kelvina. Jest to standardowa skala temperatury, ponieważ jednostką temperatury w układzie SI jest kelwin.
Zero bezwzględne to najniższa możliwa temperatura, która idealnie odzwierciedla całkowity brak energii cieplnej.
W skali Kelvina temperatura zamarzania wody wynosi 273,15, a temperatura wrzenia 373,15. Różnica jest taka sama jak w skali Celsjusza; Tylko punkt zerowy jest inny.
W ten sposób można łatwo ustalić związek między skalami Kelvina i Celsjusza.

<ol>
	<li>Protokół OpenStax. (2019). Fizyka uniwersytecka Vol. 2. [Wersja internetowa]. Pobrane z <a href="https://openstax.org/books/university-physics-volume-2/pages/1-2-thermometers-and-temperature-scales">https://openstax.org/books/university-physics-volume-2/pages/1-2-thermometers-and-temperature-scales</a></li>
</ol>

termometry gazowe i skala kelvina

Definicja temperatury w kontekście ruchu molekularnego sugeruje, że powinna istnieć najniższa możliwa temperatura, w której średnia energia kinetyczna cząsteczek wynosi zero (lub minimum dozwolone przez mechanikę kwantową). Doświadczenia potwierdzają istnienie takiej temperatury, zwanej zerem absolutnym. Absolutna skala temperatury to taka, której punkt zerowy jest zerem absolutnym. Takie skale są wygodne w nauce, ponieważ kilka wielkości fizycznych, takich jak objętość gazu doskonałego, jest bezpośrednio powiązanych z temperaturą bezwzględną.

Skala Kelvina to bezwzględna skala temperatury powszechnie stosowana w nauce.

Skala Kelvina jest częścią układu jednostek SI, więc jej rzeczywista definicja jest bardziej skomplikowana niż podana powyżej. Po pierwsze, nie definiuje się go w kategoriach temperatur zamarzania i wrzenia wody, ale w kategoriach punktu potrójnego. Punkt potrójny to unikalna kombinacja temperatury i ciśnienia, w której lód, woda w stanie ciekłym i para wodna mogą stabilnie współistnieć. Temperaturę punktu potrójnego definiuje się jako 273,16 K. Definicja ta ma tę zaletę, że chociaż temperatura zamarzania i temperatura wrzenia wody zależą od ciśnienia, istnieje tylko jedna temperatura punktu potrójnego.

Nawet przy dobrze określonych punktach skali różne termometry dają nieco inne wyniki dla innych temperatur. Dlatego wymagany jest standardowy termometr. Metrologowie wybrali do tego celu termometr gazowy o stałej objętości. Naczynie o stałej objętości wypełnione gazem poddawane jest zmianom temperatury, a zmierzona temperatura jest proporcjonalna do zmiany ciśnienia. Wyniki zależą w pewnym stopniu od wyboru gazu, ale im mniej gęsty jest gaz w bańce, tym lepiej zgadzają się wyniki dla różnych gazów. Jeśli wyniki ekstrapoluje się na gęstość zerową, wyniki są całkiem dobre, przy zerowym ciśnieniu odpowiadającym temperaturze zera absolutnego. Termometry gazowe o stałej objętości są duże i powoli osiągają równowagę, dlatego stosuje się je głównie jako wzorce do kalibracji innych termometrów.

Termometry gazowe i skala Kelvina

Definicja temperatury w kategoriach ruchu molekularnego sugeruje, że powinna istnieć najniższa możliwa temperatura, w której średnia energia kinetyczna ...

Education

JoVE Core

Physics

Fizyka

Unit 1

Jednostka 1

Temperature and Heat

Temperatura i ciepło

KEY TERMS AND CONCEPTS

Kluczowe terminy i pojęcia

kelvin temperature and gas thermometer standards

Kelvin temperature is the absolute scale used in science, and it starts at absolute zero. That zero point matches the lowest possible temperature, where molecular motion reaches zero or the minimum allowed by quantum mechanics. Scientists use this scale because some physical quantities, such as the volume of an ideal gas, depend directly on absolute temperature.

The Kelvin scale is part of the SI system of units, so its definition is more precise than simply using water’s freezing and boiling points. Instead, it is tied to the triple point of water. The triple point is the only temperature and pressure combination where ice, liquid water, and water vapor can all coexist. Its temperature is defined as 273.16 K, which is useful because it does not change with pressure the way water’s freezing and boiling points do.

Even with fixed reference points, different thermometers can give slightly different readings for other temperatures. For that reason, scientists need a standard thermometer. Metrologists use the constant-volume gas thermometer for this job. In this device, a gas in a sealed vessel stays at the same volume while temperature changes, and the temperature is found from the change in pressure.

The choice of gas can affect the results a little. However, the less dense the gas in the bulb, the better different gases agree. When the results are extrapolated to zero density, they match well, and zero pressure corresponds to absolute zero. Constant-volume gas thermometers are large and slow to reach equilibrium, so they are mainly used as standards to calibrate other thermometers.

Kelvin Temperature and Gas Thermometer Standards

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Learn how the Kelvin scale is tied to absolute zero, the triple point of water, and constant-volume gas thermometers used to calibrate other thermometers.

Kelvin Temperature and Gas Thermometer Standards | JoVE K12

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Kelvin Temperature and Gas Thermometer Standards

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