Name: gas pressure patterns in kinetic molecular theory
Uploaded: 2020-09-03T13:38:27.000Z
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Kinetic Molecular Theory and Gas Laws Explain Properties of Gas Molecules

Les observations des différentes propriétés des gaz, telles qu'exprimées par les diverses lois des gaz dérivées par Boyle, Charles, Gay-Lussac et Avogadro, suivent conceptuellement la théorie moléculaire cinétique. La pression exercée par un gaz résulte de l'impact de particules en mouvement constant sur les parois de son récipient. La diminution du volume du récipient, tout en maintenant le nombre de moles et la température constantes, rapproche les particules de gaz, réduisant leur espacement entre les particules.Dans ce volume plus petit, la densité du gaz et la fréquence de collision la fréquence des collisions molécule-paroi augmentent. Par conséquent, la pression exercée par le gaz augmente. La relation inverse entre la pression et le volume est donnée par la loi de Boyle.Ajouter plus de moles de gaz au récipient à température constante augmente la densité du gaz et, par conséquent, la fréquence de collision. Pour maintenir la pression initiale, le volume doit se dilater. Cette relation directe entre le volume et les moles est donnée par la loi d'Avogadro.Maintenant, considérez le nombre de grains de beauté est maintenu constant et la température est élevée. Parce que l'énergie cinétique moyenne des particules de gaz augmente proportionnellement avec la température, les particules entrent en collision plus fréquemment et avec force. Si le volume est maintenu constant alors que la température augmente, la densité du gaz et la fréquence de collision augmentent, et donc la pression augmentera également.La relation directe entre la pression et la température est donnée par la loi de Gay-Lussac. Si, en revanche, la pression doit rester constante avec un nombre constant de moles, alors une augmentation de la température doit s'accompagner d'une augmentation du volume pour répartir les collisions sur une plus grande surface. Cette relation directe entre le volume et la température est donnée par la loi de Charles.Enfin, selon la théorie moléculaire cinétique, les particules de gaz ne s'attirent pas ou ne se repoussent pas. Dans un mélange de différents gaz, les composants agissent indépendamment et leurs pressions individuelles restent inchangées par la présence d'un autre gaz. La pression totale du mélange est donc la somme des pressions partielles individuelles.C'est la loi de Dalton.

théorie cinétique et lois des gaz

La vérification de la théorie cinétique des gaz (TCG) et de ses postulats réside dans sa capacité à expliquer et décrire le comportement d'un gaz. Les différentes lois sur le gaz (les lois de Boyle-Mariotte, Charles, Gay-Lussac, d'Avogadro et de Dalton) peuvent être déduites des hypothèses de la théorie cinétique des gaz, qui ont conduit les chimistes à croire que les hypothèses de la théorie représentent exactement les propriétés des molécules de gaz. 
 
 <h4>La théorie cinétique des gaz explique le comportement des gaz </h4>
 
 Sachant que la pression d'un gaz est exercée par des molécules de gaz se déplaçant rapidement et qu'elle dépend directement du nombre de molécules entrant en contact avec une unité de surface de la paroi par unité de temps, la TCG explique conceptuellement le comportement d'un gaz comme suit : 
 
 <ul>
 <li>Loi de Gay-Lussac : si la température est augmentée, la vitesse moyenne et l’énergie cinétique des molécules de gaz augmentent. Si le volume est maintenu constant, la vitesse accrue des molécules de gaz entraîne des collisions plus fréquentes et plus puissantes avec les parois du récipient, ce qui augmente la pression. Ceci est également appelé la loi d'Amontons. </li>
 <li>Loi de Charles : si la température d’un gaz est augmentée, une pression constante ne peut être maintenue que si le volume occupé par le gaz augmente. Cela se traduit par de plus grandes distances moyennes parcourues par les molécules pour atteindre les parois du récipient, ainsi que par une plus grande surface de la paroi. Ces conditions diminueront à la fois la fréquence des collisions molécule-paroi et le nombre de collisions par unité de surface, dont les effets combinés équilibrent l'effet des forces de collision accrues en raison de la plus grande énergie cinétique à une température plus élevée. </li>
 <li>Loi de Boyle-Mariotte : si le volume de gaz diminue, la surface de la paroi du récipient diminue et la fréquence des collisions molécule-paroi augmente, ce qui augmente la pression exercée par le gaz. </li>
 <li>Loi d'Avogadro : à une pression et une température constantes, la fréquence et la force des collisions molécule-paroi sont constantes. Dans de telles conditions, une augmentation du nombre de molécules gazeuses nécessitera une augmentation proportionnelle du volume du récipient afin de réduire le nombre de collisions par unité de surface pour compenser l'élévation de la fréquence des collisions. </li>
 <li>Loi de Dalton : en raison des grandes distances qu'il y a entre elles, les molécules d'un gaz dans un mélange bombardent les parois du récipient avec la même fréquence, que d'autres gaz soient présents ou non, et la pression totale d'un mélange de gaz est égale à la somme des pressions (partielles) des différents gaz. </li>
 </ul>
 
 Ce texte est adapté de <a href="https://openstax.org/books/chemistry-2e/pages/9-5-the-kinetic-molecular-theory">Openstax, Chimie 2e, Section 9.5 : La théorie cinétique-moléculaire.</a>

Théorie cinétique et lois des gaz

Le test de la théorie moléculaire cinétique (KMT) et de ses postulats est sa capacité à expliquer et à décrire le comportement d’un gaz. Les différentes lois sur les gaz ...

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gas pressure patterns in kinetic molecular theory

Kinetic molecular theory explains gas pressure by linking it to the motion of gas molecules. Gas pressure comes from rapidly moving molecules hitting the walls of a container. It depends on how many molecules strike a unit area in a given time.

The theory also helps explain the main gas laws. In Gay-Lussac’s law, also called Amontons’s law, raising temperature increases the average speed and kinetic energy of gas molecules. If volume stays constant, the molecules collide with the walls more often and more forcefully, so pressure increases.

Charles’s law shows what happens when temperature rises at constant pressure. The gas must expand to keep pressure steady. That larger volume means molecules travel farther before reaching the walls, and the wall area increases too. These changes lower collision frequency and the number of collisions per unit area, which balances the stronger collisions caused by the higher kinetic energy.

Boyle’s law describes the effect of smaller volume. When gas volume decreases, the container wall area also decreases. Molecule-wall collisions become more frequent, and the pressure rises. Avogadro’s law says that at constant pressure and temperature, the collision rate and collision force stay constant. If the number of gas molecules increases, the volume must increase in proportion so the collisions per unit area can drop enough to offset the added molecules.

Dalton’s law applies to gas mixtures. Because gas molecules are far apart, one gas in a mixture strikes the container walls with the same frequency whether other gases are present or not. The total pressure of the mixture equals the sum of the partial pressures of the individual gases. These gas laws show how the assumptions of kinetic molecular theory fit the behavior of gases.

Gas Pressure Patterns in Kinetic Molecular Theory

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Gas Pressure in Mixtures: Partial Pressures

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Kinetic Molecular Theory and Gas Behavior

Kinetic molecular theory explains gas behavior at the particle level. It gives a microscopic model for what happens when pressure or temperature changes. Gas laws describe how macroscopic properties change, but they do not explain why those changes happen. The theory was put into a complete form by Rudolf Clausius in 1857. It was built from hundreds of experimental observations about gases. Those observations helped explain the different gas laws through a few basic postulates. One key idea...

kinetic molecular theory and gas laws explain properties of gas molecules

Kinetic molecular theory explains gas pressure by linking it to the motion of gas molecules. Gas pressure comes from rapidly moving molecules hitting the walls of a container. It depends on how many molecules strike a unit area in a given time. The theory also helps explain the main gas laws. In Gay-Lussac’s law, also called Amontons’s law, raising temperature increases the average speed and kinetic energy of gas molecules. If volume stays constant, the molecules collide with the walls more...

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key terms and concepts

Explore how kinetic molecular theory explains gas pressure, temperature, volume changes, and the gas laws of Boyle, Charles, Gay-Lussac, Avogadro, and Dalton.

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Gas Pressure Patterns in Kinetic Molecular Theory

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