Name: thermal equilibrium and the zeroth law
Uploaded: 2025-05-22T09:05:48.000Z
Duration: 1 min 14 s
Channel: JoVE

K12 Standards

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Chemistry

Energy

HS-PS3-4

Zeroth Law of Thermodynamics

La loi zéro de la thermodynamique stipule que si deux corps sont en équilibre thermique avec un troisième corps, ils sont également en équilibre thermique l’un avec l’autre.
Pour comprendre cela expérimentalement, considérons trois béchers remplis d’eau à trois températures différentes.
Après avoir connecté le bécher A avec B et le bécher B avec C, le transfert de chaleur aura lieu.
Après un certain temps, l’eau du bécher A arrive à l’équilibre thermique avec l’eau du bécher B, et l’eau du bécher B arrive à l’équilibre avec l’eau du bécher C.
Lors de l’enregistrement de la température des béchers, une température uniforme est observée dans les trois béchers, ce qui correspond à la loi zéro de la thermodynamique.
L’application la plus significative de la loi du zéro de la thermodynamique est les différents types de thermomètres.
Lorsqu’un thermomètre est utilisé pour mesurer la température d’un corps, celui-ci atteint l’équilibre thermique en modifiant sa propre température.
Ainsi, la température mesurée du corps est en fait la température du thermomètre.

<ol>
	<li>OpenStax. (2019). Physique universitaire Vol. 2. [Version Web]. Récupéré de <a href="https://openstax.org/books/university-physics-volume-2/pages/1-1-temperature-and-thermal-equilibrium">https://openstax.org/books/university-physics-volume-2/pages/1-1-temperature-and-thermal-equilibrium</a></li>
</ol>

zéroième loi de la thermodynamique

Expérimentalement, si l'objet A est en équilibre avec l'objet B et que l'objet B est en équilibre avec l'objet C, alors l'objet A est en équilibre avec l'objet C. Cette déclaration de transitivité est appelée la "zéroième loi de la thermodynamique". Par exemple, un bloc de métal froid et un bloc de métal chaud sont tous deux placés sur une plaque métallique à température ambiante. Finalement, le bloc froid et la plaque seront en équilibre thermique. De plus, le bloc chaud et la plaque seront en équilibre thermique. Par la zéroième loi, nous pouvons conclure que le bloc froid et le bloc chaud sont également en équilibre thermique.

Le physicien britannique Ralph Fowler a suggéré le chiffre "zéroième" dans les années 1930. À cette époque, les première, deuxième et troisième lois de la thermodynamique étaient déjà nommées et numérotées. La zéroième loi avait rarement été énoncée, mais elle devait être discutée avant les autres, donc Fowler lui a donné un plus petit numéro.

Considérons maintenant le cas où A est un thermomètre. La zéroième loi nous dit que si A indique une certaine température lorsqu'il est en équilibre avec B, et qu'il est ensuite mis en contact avec C, il n'échangera pas d'énergie avec C ; par conséquent, sa lecture de température restera la même. En d'autres termes, si deux objets sont en équilibre thermique, ils ont la même température.

Zéroième loi de la thermodynamique

Expérimentalement, si l’objet A est en équilibre avec l’objet B, et que l’objet B est en équilibre avec l’objet C, alors l’objet A est en équilibre avec l’objet C.

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KEY TERMS AND CONCEPTS

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thermal equilibrium and the zeroth law

The zeroth law of thermodynamics explains thermal equilibrium between objects. If object A is in equilibrium with object B, and object B is in equilibrium with object C, then object A is also in equilibrium with object C. This transitive relationship is the key idea behind the law.

A simple example uses metal blocks and a metal plate at room temperature. A cold metal block and a hot metal block are both placed on the plate. Over time, the cold block and the plate reach thermal equilibrium, and the hot block and the plate do too. By the zeroth law, the cold block and the hot block are then also in thermal equilibrium.

The law also helps explain how thermometers work. If a thermometer is in equilibrium with one object and then placed in contact with another object, it will not exchange energy with that object if their temperatures match. Its reading stays the same. In other words, two objects in thermal equilibrium have the same temperature.

The name zeroth law was suggested by British physicist Ralph Fowler in the 1930s. By then, the first, second, and third laws of thermodynamics had already been named. The zeroth law was less often stated, but it had to be discussed before the others, so Fowler gave it the smaller number.

Thermal Equilibrium and the Zeroth Law

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zeroth law of thermodynamics

The zeroth law of thermodynamics explains thermal equilibrium between objects. If object A is in equilibrium with object B, and object B is in equilibrium with object C, then object A is also in equilibrium with object C. This transitive relationship is the key idea behind the law. A simple example uses metal blocks and a metal plate at room temperature. A cold metal block and a hot metal block are both placed on the plate. Over time, the cold block and the plate reach thermal equilibrium, and...

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key terms and concepts

Learn how the zeroth law of thermodynamics shows that objects in thermal equilibrium have the same temperature and why this matters for thermometers.

Thermal Equilibrium and the Zeroth Law | JoVE K12

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HS-PS3-6

Thermal Equilibrium and the Zeroth Law

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