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

K12 Standards

north-carolina-k-12-science-standard-course-of-study

NC K-12 Science Standard Course of Study

9-12

Chemistry

Energy

PS.Chm.7.3

behavior-gas-molecules-molecular-diffusion-mean-free-path

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

밀폐된 향수병에는 끊임없이 운동하고 무작위로 충돌하는 기체상태의 방향성 분자가 고농도로 함유되어 있습니다. 한편 병 밖의 공기에는 근본적으로 이러한 분자가 전혀 포함되어 있지 않습니다. 병을 열면 이러한 고농도 및 저농도 영역 사이에 농도 구배가 생깁니다.

분자는 계속 무작위로 운동하면서 고농도 영역에서 저농도 영역으로 이동하게 됩니다. 농도 구배에 따라 액체나 기체가 자연적으로 혼합되고 퍼지는 현상을 분자 확산이라고 합니다. 확산은 느린 과정입니다.

기체 입자가 빠른 속도로 이동하더라도 수많은 충돌로 인해 속도와 방향이 자주 변경됩니다. 충돌 간 입자가 이동하는 평균 거리를 평균 자유 이동 경로라고 합니다. 기체 입자의 경우 평균 자유 이동 경로는 입자 밀도의 영향을 받으며 따라서 압력에도 영향을 미칩니다.

입자 밀도가 증가함에 따라 충돌 빈도도 증가합니다. 따라서 평균 자유 이동 경로가 더 짧아집니다. 마찬가지로 입자 밀도가 감소하면 충돌 빈도도 감소하여 자유 이동 경로가 길어집니다.

서로 다른 기체는 기체 입자의 속도에 따라 서로 다른 속도로 확산됩니다. 기체의 제곱근 평균 제곱 속도 및 몰질량은 반비례 관계에 있으므로 가벼운 기체는 무거운 기체보다 더 빨리 확산됩니다. 동일한 양의 암모니아 기체와 염화수소 기체 저장고 사이에 있는 유리관을 생각해 봅시다.

확산되는 기체들이 서로 부딪치면 반응하여 염화암모늄 고리를 형성합니다. 이 고리는 관의 염화수소 저장고에 더 가까이 놓이는 데 동일한 시간에 무거운 염화수소 분자보다 가벼운 암모니아 분자가 관 안에서 더 많이 이동했기 때문입니다. 분출은 기체 분자의 이동을 수반하는 또 다른 과정입니다.

이것은 기체 분자가 압력 차이에 반응하여 기체 자체의 평균 자유 이동 경로보다 지름이 훨씬 작은 구멍을 통해 이동하는 능력입니다. 이것이 헬륨 풍선이 결국 수축되는 이유입니다. 헬륨은 풍선 물질의 미세한 구멍을 통해 점차 분출됩니다.

확산과 마찬가지로 분출 속도는 기체의 제곱근 평균 제곱 속도와 몰 질량에 따라 달라집니다. 구체적으로 보면 분출 속도는 기체의 몰 질량의 제곱근에 반비례합니다. 그러므로 무거운 기체는 가벼운 기체보다 더 천천히 분출됩니다.

어떤 두 종류의 기체에 대해 분출 속도의 비율은 몰 질량의 역비의 제곱근입니다. 이것을 그레이엄의 법칙이라고 합니다. 같은 압력으로 팽창된 두 개의 풍선을 생각해 보세요.

하나는 헬륨을 채웠고 다른 하나는 산소를 채웠습니다. 공기 중에 있는 헬륨 풍선의 부력으로 볼 수 있듯이 헬륨은 산소보다 몰 질량이 낮습니다. 그레이엄의 법칙을 헬륨과 산소에 적용하면 헬륨이 산소보다 2.8배 더 빨리 유출된다는 것을 알 수 있습니다.

따라서 헬륨 풍선은 산소 풍선보다 더 빨리 수축됩니다.

기체 분자의 거동: 분자 확산, 평균 자유 경로 및 유출

기체 분자는 엄청난 속도(초당 수백 미터)로 이동하지만 다른 기체 분자와 충돌하고 원하는 목표에 도달하기 전에 다양한 방향으로 이동합니다. 실온에서 기체 분자는 초당 수십억 번의 충돌을 경험합니다. 평균 자유 경로는 분자가 충돌 사이에 이동하는 평균 거리입니다. 평균 자유 행로는 압력이 감소함에 따라 증가합니다. 일반적으로 기체 분자의 평균 자유 행로는 분자 직경의 수백 배입니다.

일반적으로 가스 샘플이 밀폐된 용기의 한 부분에 유입되면 해당 분자가 용기 전체에 매우 빠르게 분산됩니다. 농도 차이에 따라 분자가 공간에 분산되는 이 과정을 확산이라고 합니다. 물론 기체 원자나 분자는 농도 구배를 인식하지 못합니다. 이것은 단순히 무작위로 움직입니다. 농도가 높은 지역은 농도가 낮은 지역보다 입자가 더 많기 때문에 농도가 높은 지역에서 낮은 지역으로 종의 순 이동이 발생합니다. 폐쇄된 환경에서는 확산으로 인해 궁극적으로 전체 가스 농도가 동일해집니다. 기체 원자와 분자는 계속 움직이지만 두 전구의 농도가 동일하므로 전구 사이의 이동 속도는 동일합니다(분자의 순 이동은 발생하지 않음). 단위 시간당 특정 영역을 통과하는 가스의 양이 확산 속도입니다.

<img alt="Eq1" src="https://www.jove.com/files/core/CDNSource/lessons/1044/1044_Equations-01.png" style="height: 40px;" />

확산 속도는 농도 구배(한 지점에서 다른 지점으로의 농도 증가 또는 감소), 확산에 사용할 수 있는 표면적, 가스 입자가 이동해야 하는 거리 등 여러 요인에 따라 달라집니다.

확산과 유사한 기체 종의 이동과 관련된 과정은 삼출, 즉 풍선의 핀홀과 같은 작은 구멍을 통해 기체 분자가 진공 속으로 빠져나가는 과정입니다. 확산 속도와 유출 속도는 모두 관련된 가스의 몰 질량에 따라 다르지만 속도는 동일하지 않습니다. 그러나 요율의 비율은 동일합니다.

벽이 다공성인 용기에 혼합 가스를 넣으면 벽에 있는 작은 구멍을 통해 가스가 새어 나옵니다. 가벼운 가스는 무거운 가스보다 작은 구멍을 더 빠르게(더 빠른 속도로) 통과합니다. 1832년에 Thomas Graham은 다양한 기체의 분출 속도를 연구하고 Graham의 분출 법칙을 공식화했습니다. 기체의 분출 속도는 입자 질량의 제곱근에 반비례합니다.

<img alt="Eq2" src="https://www.jove.com/files/core/CDNSource/lessons/1044/1044_Equations-02.png" style="height: 40px;" />

이는 A와 B라는 두 기체가 동일한 온도와 압력에 있을 경우, 이 기체의 분출 속도 비율은 입자 질량의 제곱근 비율에 반비례한다는 의미입니다.

<img alt="Eq3" src="https://www.jove.com/files/core/CDNSource/lessons/1044/1044_Equations-03.png" style="height: 40px;" />

이 관계는 가벼운 가스일수록 유출 속도가 더 높다는 것을 나타냅니다.

예를 들어, 헬륨으로 채워진 고무 풍선은 공기로 채워진 고무 풍선보다 더 빨리 수축합니다. 왜냐하면 고무 구멍을 통한 삼출 속도는 공기 분자보다 가벼운 헬륨 원자의 경우 더 빠르기 때문입니다.

이 문서는 에서 발췌되었습니다 <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.</a>

기체 분자는 엄청난 속도(초당 수백 미터)로 이동하지만 다른 기체 분자와 충돌하여 많은 ...

Education

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JoVE Core

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하나

Gases

기체

KEY TERMS AND CONCEPTS

주요 용어 및 개념

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

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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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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...

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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...

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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...

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Gas Pressure Patterns in Kinetic Molecular Theory

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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...

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Real Gases: When the Ideal Gas Law Breaks Down

Real gases are gases that do not always follow the ideal gas law, PV = nRT, especially when pressure is high or temperature is low. The ideal gas model assumes gas particles have no attractive or repulsive forces and take up negligible space compared with the container. At room temperature and 1 atm or less, many gases behave close to ideally. When conditions change, the measured relationships between pressure, volume, and temperature can drift away from the ideal prediction. One way to see...

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

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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

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SC.912.P.10

SC.912.P.10.5

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New York State Science Learning Standards

HS. Structure and Properties of Matter

HS-PS1-9.

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Chemistry is the study of matter and the changes it undergoes. Matter is anything that has mass and occupies space. Matter is all around us; the air, ...

Classifying Matter by Composition

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Surface Tension
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States of Matter and Phase Changes

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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

When a liquid vaporizes in a closed container, gas molecules cannot escape. As these gas phase molecules move randomly about, they will occasionally ...

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

Heating a crystalline solid increases the average energy of its atoms, molecules, or ions, and the solid gets hotter. At some point, the added energy ...

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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

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Constant Volume Calorimetry

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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

Gas pressure is caused by force exerted by gas molecules colliding with the surfaces of objects. Although the force of each collision is very small, any ...

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

Through experiments, scientists established the mathematical relationships between pairs of variables, such as pressure and temperature, pressure and ...

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

The volume occupied by one mole of a substance is its molar volume. The ideal gas law, PV = nRT, &nbsp;suggests that the volume of a given quantity of gas ...

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

	Preparation of the LaboratoryExpand
	Here, we show the laboratory preparation for 10 students ...

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

	Determining the Mass of the Unknown LiquidExpand
	According to the ideal gas law for a given ...

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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