Name: kinetic molecular theory and gas behavior
Uploaded: 2020-09-03T13:38:26.000Z
Duration: 2 min 43 s
Channel: JoVE

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NC K-12 Science Standard Course of Study

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Chemistry

Energy

PS.Chm.7.3

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Basic Postulates of Kinetic Molecular Theory: Particle Size, Energy, and Collision

В то время как газовые законы характеризуют взаимосвязи между различными свойствами идеальных газов, молекулярно-кинетическая теория объясняет, почему газы подчиняются этим законам. Теория основана на нескольких предположениях или постулатах. Первое предположение заключается в том, что частицы газа незначительны по размеру.Газ это в основном пустое пространство, заполненное мелкими частицами, разнесенными на расстояния, намного превышающие их собственные размеры. Их общий объем ничтожно мал по сравнению с общим объемом, в котором содержится газ. В отличие от твердых тел и жидкостей, которые невозможно сжать из-за малого расстояния между частицами, газы обладают высокой сжимаемостью.Частицы газа находятся в постоянном движении по прямым линиям в случайных направлениях. Их пути меняются только тогда, когда они сталкиваются с другими частицами или со стенками емкости, в которой находятся. Второе предположение состоит в том, что частицы газа совершают идеально упругие столкновения.Они сталкиваются и отскакивают друг от друга, не слипаясь. Это можно сравнить со столкновениями бильярдных шаров. Когда частицы газа сталкиваются, они обмениваются энергией друг с другом, но при этом не происходит чистой потери энергии.Иными словами, полная энергия системы остается постоянной. Частицы газа постоянно движутся;следовательно, они обладают кинетической энергией. Таким образом, третье предположение гласит, что средняя кинетическая энергия газа пропорциональна его абсолютной температуре в Кельвинах.Это означает, что кинетическая энергия увеличивается с температурой, и, следовательно, частицы движутся быстрее. При более высоких температурах их скорость увеличивается. И наоборот, с понижением температуры уменьшается кинетическая энергия частиц, и они движутся медленнее.При заданной температуре все газы, независимо от их молекулярной массы, имеют одинаковую среднюю кинетическую энергию. Кинетическая энергия равна квадрату массы, умноженной на скорость. Таким образом, чтобы разные газы имели одинаковую среднюю кинетическую энергию, их частицы должны перемещаться с разными средними скоростями.Следовательно, более тяжелые газы имеют более низкие средние скорости, в то время как более легкие газы имеют более высокие средние скорости. Например, гелий и неон при одинаковой температуре имеют одинаковую среднюю кинетическую энергию. Однако из-за разницы масс атомы неона движутся намного медленнее, чем атомы гелия.

Молекулярно-кинетическая теория: основные постулаты

Эмпирическое уравнение идеального газа описывает поведение газов, устанавливая связи между их макроскопическими свойствами. Например, в законе Чарльза говорится, что объем и температура напрямую связаны. Таким образом, газы расширяются при нагревании при постоянном давлении. Хотя газовые законы объясняют, как макроскопические свойства меняются относительно друг друга, они не дают обоснованния этому. 
 
 Молекулярно-кинетическая теория — это микроскопическая модель, которая помогает понять, что происходит с частицами газа на молекулярном или атомном уровне при таких условиях, как изменение давления или температуры. В 1857 году Рудольф Клаузиус опубликовал полную и удовлетворительную форму теории, которая эффективно объясняет различные газовые законы постулатами, которые были разработаны на основе сотен экспериментальных наблюдений за поведением газов. 
 
 Основные особенности этой теории: 
 
 <ol>
 <li>Газы состоят из частиц (атомов или молекул), которые находятся в непрерывном движении и двигаются по прямым и изменяющимся траекториям только при столкновении с другими молекулами или со стенками контейнера. 
 Проверьте образец аргона-газа при стандартной температуре и давлении. Показано, что только 0.01% объема представлен атомами со средним расстоянием 3.3 нм (атомный радиус аргона составляет 0.097 нм) между двумя атомами аргона. Расстояние намного больше, чем его собственный размер. </li>
 <li>Молекулы, составляющие газ, пренебрежимо малы по сравнению с расстояниями между ними. Таким образом, суммарный объем всех частиц газа пренебрежимо мал относительно общего объема контейнера. Частицы считаются “точками”, которые имеют массу , но пренебрежимо малый объём. </li>
 <li>Давление, оказываемое газом в контейнере, возникает в результате столкновений между молекулами газа и стенками контейнера. </li>
 <li>Молекулы газа не оказывают притягивающих или отталкивающих сил друг на друга или стенки контейнера, поэтому их столкновения эластичны (не влекут за собой потери энергии). 
 При упругих столкновениях энергия передается между ударяющимися частицами. Таким образом, средняя кинетическая энергия частиц остается постоянной и не меняется со временем. </li>
 <li>Средняя кинетическая энергия молекул газа пропорциональна температуре газа в Кельвинах. 
 Все газы, независимо от их молекулярной массы, имеют одинаковую среднюю кинетическую энергию при одинаковой температуре. </li>
 </ol>
 
 Этот текст адаптирован из <a href=""https://openstax.org/books/chemistry-2e/pages/9-5-the-kinetic-molecular-theory"">Openstax, Химия 2е изд., Раздел 9.5 Молекулярно-кинетическая теория</a>. "

Эмпирическое уравнение идеального газа описывает поведение газов путем установления взаимосвязи между их макроскопическими свойствами. Для...

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KEY TERMS AND CONCEPTS

ОСНОВНЫЕ ТЕРМИНЫ И ПОНЯТИЯ

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 is that gases are made of particles, either atoms or molecules, that move constantly. They travel in straight lines until they collide with other particles or with the walls of a container. A sample of argon gas at standard temperature and pressure shows that the particles take up only a tiny part of the total volume. The average distance between two argon atoms is much larger than the size of the atoms themselves. Because of this, gas particles are treated as points with mass but negligible volume.

Gas pressure comes from collisions between gas molecules and the walls of the container. The particles do not attract or repel each other, and they do not interact with the container walls through such forces. For that reason, their collisions are elastic, which means no energy is lost in the collision. Energy can still be transferred between colliding particles, but the average kinetic energy stays constant over time.

The average kinetic energy of gas particles depends on the kelvin temperature of the gas. It is proportional to temperature. At the same temperature, gases with different molecular masses have the same average kinetic energy.

Kinetic Molecular Theory and Gas Behavior

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definition and measurement of pressure: atmospheric pressure, barometer, and manometer

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Pressure Units and Tools for Gas Measurement

Pressure is the force applied to a given area, and gas pressure comes from gas molecules colliding with surfaces. Each collision is tiny, but many collisions over a small area can create high pressure. Pressure increases when force increases or when the area gets smaller. It decreases when force drops or when the area gets larger. Pressure is measured in pascals, or Pa, in the SI system. One pascal equals 1 newton per square meter, and a newton is a unit of force equal to 1 kg·m/s2. A pascal...

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Stoichiometry of Gases with the Ideal Gas Law

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basic postulates of kinetic molecular theory: particle size, energy, and collision

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

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Gas Pressure Patterns in Kinetic Molecular Theory

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kinetic molecular theory: molecular velocities, temperature, and kinetic energy

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Gas Particle Speed Distributions and Temperature

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key terms and concepts

Explore how kinetic molecular theory explains gas pressure, particle motion, elastic collisions, and why average kinetic energy depends on kelvin temperature.

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PS.Chm.7.2

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Kinetic Molecular Theory and Gas Behavior

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