Name: gas particle motion, diffusion, and effusion
Uploaded: 2020-09-03T13:38:27.000Z
Duration: 3 min 48 s
Channel: JoVE

K12 Standards

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NC K-12 Science Standard Course of Study

9-12

Chemistry

Energy

PS.Chm.7.3

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Behavior of Gas Molecules: Molecular Diffusion, Mean Free Path, and Effusion

香水の閉じたボトルには 常に移動し ランダムに衝突している ガス状の芳香族分子が 高濃度で含まれています 一方 ボトルの外の空気には これらの分子は ほとんど含まれていません ボトルを開くと これらの高濃度と 低濃度の領域の間に 濃度勾配が 確立されます 分子はランダムに動き続け 全体としては 高濃度領域から 低濃度領域へと移動します 濃度勾配に反応して 液体や気体が 自然に混合したり 広がったりすることを 分子拡散といいます 拡散はゆっくりとした プロセスです 気体の粒子が 高速で移動していても 多数の衝突により 速度と方向が 頻繁に変化します 粒子が衝突の間に 移動する平均距離は その平均自由行程として 知られています 気体粒子の平均自由行程は 粒子密度の影響を受け 圧力にも影響されます 粒子密度が高くなると 衝突頻度も高くなります そのため 平均自由行程は 短くなります 同様に 粒子密度が低下すると 衝突頻度も低下し 平均自由行程は長くなります 異なるガスは ガス粒子によって 異なる速度で拡散します 二乗平均平方根速度（RMS）と 気体のモル質量は 反比例関係にあるので 軽い気体は 重い気体よりも速く拡散します 同量のアンモニアガスと 塩化水素ガスの 間にあるガラス管を 考えてみましょう 拡散する気体が出会うと 反応して 塩化アンモニウムの リングを形成します 同じ時間内に 軽い アンモニア分子は 重い塩化水素分子よりも 管の中を 遠くまで移動したため リングは 塩化水素の端に近くなります 噴出は 気体分子の移動を伴う 別のプロセスです これは 圧力差に反応して ガス分子がガスの 平均自由行程よりも はるかに小さい直径の穴を 通過する能力のことです これが ヘリウム風船が 最終的に収縮する理由です ヘリウムが風船の 材料の小さな気孔から 徐々に噴出していきます 拡散と同様に 噴出の速度は ガスのRMS速度と モル質量に依存します 具体的には 噴出速度は ガスのモル質量の 平方根に反比例します したがって重いガスは軽い ガスよりもゆっくりと噴出します どのような2つの気体でも その噴出速度の比は その気体の モル質量の逆比の 平方根になります これをグラハムの法則と呼びます 同じ圧力に膨らませた 2つの風船を考えてみましょう ヘリウムで満たされたものと 酸素で満たされたものです ヘリウムバルーンの空気中の 浮力によって示されるように ヘリウムは酸素よりも 低いモル質量を持っています グラハムの法則を ヘリウムと酸素に適用すると ヘリウムは酸素の2.8倍の 速さで噴出することになります したがって ヘリウム気球は 酸素気球よりも 早く収縮します

拡散と流出

気体分子は非常に高速（毎秒数百メートル）で移動するが、他の気体分子と衝突し、目的のターゲットに到達する前にさまざまな方向に移動します。 室温では、気体分子は毎秒数十億の衝突を経験します。 平均自由行程とは、分子が衝突の間に移動する平均距離です。 平均自由行程は圧力が低いほど長くなり、一般に、気体分子の平均自由行程は分子の直径の数百倍になります。 
 
 一般的に、気体試料が密閉容器の一部に導入されると、その分子は非常に素早く容器全体に分散します。このような濃度の違いに応じて分子が空間内で分散する過程を拡散と呼びます。 もちろん、気体の原子や分子は濃度勾配を認識しません。単にランダムに移動するだけで、濃度の高い領域は濃度の低い領域よりも粒子が多いため、高濃度から低濃度領域への正味の移動が発生します。 密閉された環境では、拡散によって最終的に気体の濃度が均等になります。 気体原子と分子は移動し続けますが、両方のバルブの濃度が同じであるため、バルブ間の移動速度は等しくなります（分子の正味の移動はない）。 単位時間あたりに一部の領域を通過する気体の量が、拡散率です。 
 
 <img alt="Eq1" src="https://www.jovecore.com/CDNSource/lessons/1044/1044_Equations-01.png" style="height: 40px;" />
 
 拡散率は、濃度勾配（ある地点から別の地点への濃度の増減）、拡散可能な表面積の量、および気体粒子が移動する必要がある距離など、いくつかの要因に依存します。 
 
 拡散と同じように気体が移動する過程として、気体分子が小さな穴（バルーンのピンホールなど）を通って真空に放出される「流出」があります。 拡散と流出の速度は、どちらも関与する気体のモル質量に依存するが、その速度は等しくありません。ただし、その速度の比率は同じです。 
 
 浸透性の壁を持つ容器に気体の混合物を入れると、気体は壁の小さな開口部を通って排出されていきます。 軽い気体は、重い気体よりも（高い速度で）小さな開口部をより速く通過します。 1832 年、トーマス・グラハムはさまざまな気体の流出率を調査し、グレアムの流出法則を制定しました。ガスの流出率は、その粒子の質量の平方根に反比例します。 
 
 <img alt="Eq2" src="https://www.jovecore.com/CDNSource/lessons/1044/1044_Equations-02.png" style="height: 40px;" />
 
 これは、 2 つの気体 A と B が同じ温度と圧力である場合、その流出率の比は、粒子の質量の平方根の比に反比例することを意味します。 
 
 <img alt="Eq3" src="https://www.jovecore.com/CDNSource/lessons/1044/1044_Equations-03.png" style="height: 40px;" />
 
 この関係性はより軽い気体がより高い流出率を有すことを示します。 
 
 例えば、ヘリウム充填されたゴム製バルーンは、空気が充填されたバルーンよりも速く収縮します。これは、ゴムの孔を通る流出の発生率が、空気分子よりも軽いヘリウム原子の方が速いためです。 
 
 この文章は <a href="https://openstax.org/books/chemistry-2e/pages/9-4-effusion-and-diffusion-of-gases">、 Openstax 、 Chemistry 2e 、 Section 9.4 ： effusion and Diffusion of gases に基づいています。</a>

気体分子は猛烈な速度(秒速数百メートル)で移動しますが、他の気体分子と衝突して多くの...

Education

JoVE Core

化学

Gases

気体

KEY TERMS AND CONCEPTS

主要用語と概念

gas particle motion, diffusion, and effusion

Gas particle motion, diffusion, and effusion explain how gases spread and escape in everyday settings. Gas molecules move at very high speeds, but they collide with other gas molecules and change direction many times before reaching a target. At room temperature, a gas molecule can experience billions of collisions each second.

The mean free path is the average distance a molecule travels between collisions. This distance becomes larger when pressure decreases. In general, the mean free path of a gas molecule is hundreds of times greater than the molecule’s diameter.

Diffusion is the spread of gas particles through space because of differences in concentration. When a gas is added to one part of a closed container, its molecules quickly disperse throughout the container. The molecules move randomly, but the net movement is from higher concentration to lower concentration. In a closed environment, diffusion eventually leads to equal concentrations throughout. The gas particles still move, but there is no net transfer between regions when the concentrations are the same.

The rate of diffusion is the amount of gas that passes through an area in a given time. It depends on the concentration gradient, the available surface area, and the distance the particles must travel. A related process is effusion, which is the escape of gas molecules through a tiny opening, such as a pinhole in a balloon into a vacuum. Diffusion and effusion rates both depend on molar mass, but the rates are not the same.

If a mixture of gases is placed in a container with porous walls, the gases effuse through the small openings. The lighter gases pass through more quickly than the heavier gases. Thomas Graham studied these rates in 1832 and formed Graham’s law of effusion. This law states that the rate of effusion is inversely proportional to the square root of the mass of the particles. For two gases at the same temperature and pressure, the ratio of their effusion rates follows the same relationship. A helium-filled rubber balloon, for example, deflates faster than an air-filled balloon because helium atoms effuse faster through the rubber pores than air molecules.

Gas Particle Motion, Diffusion, and Effusion

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

definition-measurement-pressure-atmospheric-pressure-barometer

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...

gas laws: boyle's, gay-lussac, charles', avogadro's, and ideal gas law

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How Gas Pressure, Volume, and Temperature Change

Gas pressure, volume, temperature, and amount are linked by several gas laws. Scientists found these relationships by studying how a confined gas changes when one variable is held constant and another changes. These patterns apply to an ideal gas, which is a useful model for gases under low pressure and high temperature. Gay-Lussac’s law, also called Amontons’s law, connects pressure and temperature. If gas is trapped in a rigid container, the volume and number of moles stay constant. When the...

applications of the ideal gas law: molar mass, density, and volume

applications-of-the-ideal-gas-law-molar-mass-density-and-volume

Ideal Gas Law at STP and Gas Density

The ideal gas law links pressure, volume, number of moles, and temperature. It helps explain how gas volume changes when pressure or temperature changes. At standard temperature and pressure, or STP, the values are 273.15 K and 1 atm. At STP, one mole of an ideal gas occupies about 22.4 L. This is called the standard molar volume. The gas can be hydrogen, oxygen, argon, or carbon dioxide, and the volume is still about 22.4 liters. Half a mole occupies 11.2 L, and 2 moles occupy 44.8 L. The...

mixtures of gases: dalton's law of partial pressures and mole fractions

mixtures-of-gases-dalton-s-law-of-partial-pressures-and-mole-fractions

Gas Pressure in Mixtures: Partial Pressures

Gas pressure in mixtures is described by partial pressure and mole fraction. When gases do not chemically react, each gas in the mixture acts as if it were alone in the container. The pressure from one gas is called its partial pressure. For a mixture of three gases, A, B, and C, the total pressure equals the sum of their partial pressures: PA, PB, and PC. This is Dalton's law of partial pressures. It states that the total pressure of a mixture of ideal gases is the sum of the pressures from...

chemical stoichiometry and gases: using ideal gas law to determine moles

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Stoichiometry of Gases with the Ideal Gas Law

Chemical stoichiometry links the amounts of reactants and products in a chemical reaction. For gases, those amounts can also be measured by volume. If a gas’s volume, pressure, and temperature are known, the ideal gas equation can be used to find the number of moles present. The same idea works in reverse. If the moles of a gas are known, its volume can be found at any temperature and pressure. The transcript gives an example using 8.88 g of gallium reacting with excess hydrochloric acid.

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

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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

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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

Gas particle speed distributions and temperature are key ideas in the kinetic molecular theory. This theory explains the gas laws by describing how gas molecules move, collide, and share energy. Gas molecules do not all move at the same speed. A gas sample has an average speed and an average kinetic energy, but individual molecules move at different speeds. Their collisions are elastic, which means momentum is conserved. Because so many molecules collide, the overall speed distribution stays...

behavior of gas molecules: molecular diffusion, mean free path, and effusion

Gas particle motion, diffusion, and effusion explain how gases spread and escape in everyday settings. Gas molecules move at very high speeds, but they collide with other gas molecules and change direction many times before reaching a target. At room temperature, a gas molecule can experience billions of collisions each second. The mean free path is the average distance a molecule travels between collisions. This distance becomes larger when pressure decreases. In general, the mean free path...

real gases: effects of intermolecular forces and molecular volume deriving van der waals equation

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Real Gases: When the Ideal Gas Law Breaks Down

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key terms and concepts

Explore how gas molecules move, diffuse, and effuse, plus why lighter gases pass through tiny openings faster than heavier gases.

Gas Particle Motion, Diffusion, and Effusion | JoVE K12

chemistry

JoVE Core 化学は、簡潔で理解しやすいアニメーションビデオレッスンを使用して、一般的な化学の概念を生き生きとしたものにします。さらに、活動する科学者のビデオでは、現在世界中の実験室で行われている古典的そして独創的な研究・実験をお見せします。

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Ohio’s Learning Standards and Model Curriculum

Interactions Of Matter

Gas laws

Virginia  Standards of Learning

HIgh School

CH.6

CH.6.b

Texas Essential Knowledge and Skills

High School

CHEM.10

CHEM.10.A

Alabama Course of Study Science

Matter and Its Interactions

9-12.C.1.4.e

9-12.C.4.7

9-12.C.4.7.a

Florida Department of Education

Physical Science

SC.912.P.10

SC.912.P.10.5

new-york-state-science-learning-standards

New York State Science Learning Standards

HS. Structure and Properties of Matter

HS-PS1-9.

Classifying Matter by State

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Classifying Matter by Composition

Matter: Pure Substances and Mixtures
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Physical Properties of Matter

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Intermolecular vs Intramolecular Forces

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Intermolecular Forces

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Surface Tension, Capillary Action, and Viscosity

Surface Tension
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States of Matter and Phase Changes

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Phase Transitions

Whether solid, liquid, or gas, a substance&#39;s state depends on the order and arrangement of its particles (atoms, molecules, or ions). Particles in the ...

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Phase Transitions: Vaporization and Condensation

The physical form of a substance changes on changing its temperature. For example, raising the temperature of a liquid causes the liquid to vaporize ...

Vapor Pressure

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Clausius-Clapeyron Equation

The equilibrium between a liquid and its vapor depends on the temperature of the system; a rise in temperature causes a corresponding rise in the vapor ...

Phase Transitions: Melting and Freezing

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Phase Transitions: Sublimation and Deposition

Some solids can transition directly into the gaseous state, bypassing the liquid state, via a process known as sublimation. At room temperature and ...

Heating and Cooling Curves

When a substance&#8212;isolated from its environment&#8212;is subjected to heat changes, corresponding changes in temperature and phase of the substance ...

Phase Diagrams

A phase diagram combines plots of pressure versus temperature for the liquid-gas, solid-liquid, and solid-gas phase-transition equilibria of a substance. ...

Use models to explain how changes in energy affect the arrangement and movement of the particles in solids, liquids, and gases, as well as the relative strengths of their intermolecular forces.

PS.Chm.7.1

Energy Basics

Chemical reactions, such as those that occur when you light a match, involve changes in energy as well as matter.

Chemical changes and their accompanying ...

First Law of Thermodynamics

Energy Conservation

Energy can be converted from one form into another, but all of the energy present before a change occurs always exists in some form ...

Internal Energy

The total of all possible kinds of energy present in a substance is called the internal energy (U), sometimes symbolized as E. Suppose a system with ...

Quantifying Heat

Thermal Energy&#160;

Microscopically, thermal energy is the kinetic energy associated with the random motion of atoms and molecules. Temperature is a ...

Quantifying Work

As a system undergoes a change, its internal energy can change, and energy can be transferred from the system to the surroundings, or from the ...

Enthalpy

Chemists ordinarily use a property known as enthalpy (H) to describe the thermodynamics of chemical and physical processes. Enthalpy is defined as the sum ...

Thermochemical Equations

For a chemical reaction (the system) carried out at constant pressure &ndash; with the only work done caused by expansion or contraction &ndash; the ...

Constant Pressure Calorimetry

Calorimetry is a technique used to measure the amount of heat involved in a chemical or physical process or to measure the heat transferred to or from a ...

Constant Volume Calorimetry

Calorimeters are useful to determine the heat released or absorbed by a chemical reaction. Coffee cup calorimeters are designed to operate at constant ...

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Using Differential Scanning Calorimetry to Measure Changes in Enthalpy

Source: Laboratory of Dr. Terry Tritt &#8212; Clemson University
Differential Scanning Calorimetry (DSC) is a method of thermodynamic analysis based on ...

Hess's Law

There are two ways to determine the amount of heat involved in a chemical change: measure it experimentally, or calculate it from other experimentally ...

Standard Enthalpy of Formation

Enthalpy changes are typically tabulated for reactions in which both the reactants and products are at the same conditions. A standard state is a commonly ...

Enthalpies of Reaction

Hess&rsquo;s law can be used to determine the enthalpy change of any reaction if the corresponding enthalpies of formation of the reactants and products ...

Use mathematics and computational thinking to execute simple calorimetric calculations based on the Law of Conservation of Energy.

PS.Chm.7.2

Definition and Measurement of Pressure: Atmospheric Pressure, Barometer, and Manometer

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Gas Laws: Boyle's, Gay-Lussac, Charles', Avogadro's, and Ideal Gas Law

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Applications of the Ideal Gas Law: Molar Mass, Density, and Volume

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Mixtures of Gases: Dalton's Law of Partial Pressures and Mole Fractions

Unless individual gases chemically react with each other, the individual gases in a mixture of gases do not affect each other&rsquo;s pressure. Each gas ...

Chemical Stoichiometry and Gases: Using Ideal Gas Law to Determine Moles

Chemical stoichiometry describes the quantitative relationships between reactants and products in chemical reactions.

In addition to measuring quantities ...

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

The ideal-gas equation, which is empirical, describes the behavior of gases by establishing relationships between their macroscopic properties. For ...

Kinetic Molecular Theory and Gas Laws Explain Properties of Gas Molecules

The test of the kinetic molecular theory (KMT) and its postulates is its ability to explain and describe the behavior of a gas. The various gas laws ...

Kinetic Molecular Theory: Molecular Velocities, Temperature, and Kinetic Energy

The kinetic molecular theory qualitatively explains the behaviors described by the various gas laws. The postulates of this theory may be applied in a ...

Although gaseous molecules travel at tremendous speeds (hundreds of meters per second), they collide with other gaseous molecules and travel in many ...

Real Gases: Effects of Intermolecular Forces and Molecular Volume Deriving Van der Waals Equation

Thus far, the ideal gas law, PV = nRT, has been applied to a variety of different types of problems, ranging from reaction stoichiometry and empirical and ...

Ideal Gas Law

Source: Laboratory of Dr. Andreas Z&#252;ttel - Swiss Federal Laboratories for Materials Science and Technology
The ideal gas law describes the behavior ...

Derivation of the Ideal Gas Law
Gases are a fundamental state of matter. A gas is a collection of molecules that have a significant distance between their ...

Source: Smaa Koraym at Johns Hopkins University, MD, USA

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Use mathematics and computational thinking to explain the relationships among pressure, temperature, volume, and quantity of gas, both qualitatively and quantitatively.

Understand the relationship among pressure, temperature, volume, and phase.

Gas Particle Motion, Diffusion, and Effusion

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