Name: gas pressure patterns in kinetic molecular theory
Uploaded: 2020-09-03T13:38:27.000Z
Duration: 2 min 34 s
Channel: JoVE

K12 Standards

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Chemistry

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PS.Chm.7.3

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Kinetic Molecular Theory and Gas Laws Explain Properties of Gas Molecules

זיהוי תכונות שונות של גזים על פי חוקי הגזים השונים כפי שניסחו אותם בויל, צ'רלס גה-ליסאק ואבוגדרו, מתאימה לעקרונות המתוארים בתיאוריה קינטית של הגזים. הלחץ שמפעיל הגז נובע מהתנגשויות בין חלקיקים נעים לבין דפנות המכל בו נמצא הגז. הקטנת נפח המכל, תוך שמירה על קביעות של מספר המולים והטמפרטורה, מצופפת את חלקיקי הגז ומקטינה את המרווח בין החלקיקים.כשנפח הגז קטן יותר, הצפיפות, ותדירות ההתנגשויות בין החלקיקים לדפנות עולה. מכאן שהלחץ המופעל על ידי הגז גדל. היחס ההפוך בין לחץ לנפח מתואר בחוק בויל.הגדלת מספר המולים של הגז במכל בטמפרטורה קבועה מגדילה את צפיפות הגז ומכאן שגם את תדירות ההתנגשויות. כדי לשמור על הלחץ הראשוני, הנפח צריך לגדול. הקשר הישר בין נפח למולים נקבע על פי חוק אבוגדרו.כעת, הניחו שמספר המולים נותר קבוע והטמפרטורה עולה. משום שהאנרגיה הקינטית הממוצעת של חלקיקי הגז גדלה ביחס ישר לעליית הטמפרטורה, החלקיקים מתנגשים לעיתים תכופות יותר ובכוח רב יותר. אם הנפח נותר קבוע בזמן שהטמפרטורה עולה, צפיפות הגז ותדירות ההתנגשויות גדלות, ומכאן שגם הלחץ יגדל.היחס הישר בין לחץ לטמפרטורה נקבע על ידי חוק גה-ליסאק. לעומת זאת, אם הלחץ הוא זה שנותר קבוע יחד עם מספר מולים קבוע, אז עלייה בטמפרטורה מוכרחה להיות מלווה בהגדלת הנפח על מנת לפזר את ההתנגשויות על פני שטח פנים גדול יותר. היחס הישר בין נפח לטמפרטורה נקבע בחוק צ'רלס.לבסוף, על פי התאוריה הקינטית של גזים, חלקיקי גז לא נמשכים זה לזה ולא דוחים זה את זה. בתערובת של גזים שונים, הרכיבים מתנהגים באופן עצמאי והלחץ של כל אחד מהם לא מושפע מנוכחותם של גזים אחרים. הלחץ הכולל של התערובת הוא סך הלחצים החלקיים של הגזים השונים.זהו חוק דלטון.

תיאוריה מולקולרית קינטית וחוקי גז מסבירים את המאפיינים של מולקולות גז

<div style="direction:rtl">המבחן של התיאוריה המולקולרית הקינטית (KMT) והנחותיה הוא יכולתה להסביר ולתאר את התנהגותו של גז. ניתן לגזור את חוקי הגז השונים (חוקי בויל, צ'ארלס, גה-ליסאק, אבוגדרו ודלטון) מההנחות של ה-KMT, שהוביל את הכימאים להאמין שהנחות התיאוריה מייצגות במדויק את תכונות מולקולות הגז. <h4>התיאוריה המולקולרית הקינטית מסבירה את התנהגות הגזים</h4> נזכיר שלחץ הגז מופעל על ידי מולקולות גז הנעות במהירות ותלויות ישירות במספר המולקולות הפוגעות ביחידת שטח של הקיר ליחידת זמן, ה-KMT מסביר באופן רעיוני את התנהגותו של גז באופן הבא: <ul style="padding-right: 35px; list-style-type: disc;"> <li style="text-align: right;">חוק של גה-ליסאק: אם הטמפרטורה מוגברת, המהירות הממוצעת והאנרגיה הקינטית של מולקולות הגז גדלות. אם הנפח נשמר קבוע, המהירות המוגברת של מולקולות הגז גורמות להתנגשויות תכופות ועוצמתיות יותר עם דופן המיכל, ולכן מגדילה את הלחץ. זה מכונה גם חוק אמונטונס.</li> <li style="text-align: right;">חוק צ'ארלס: אם הטמפרטורה של גז מוגברת, לחץ קבוע עשוי להישמר רק אם הנפח התפוס על ידי הגז גדל. זה יביא למרחקים ממוצעים גדולים יותר שהמולקולות נסעו כדי להגיע לדופן המיכל, כמו גם להגדלת שטח פני הקיר. תנאים אלו יפחיתו הן את תדירות ההתנגשויות של מולקולה-דופן והן את מספר ההתנגשויות ליחידת שטח, שהשפעותיהן המשולבות מאזנות את השפעת כוחות ההתנגשות המוגברים עקב האנרגיה הקינטית הגדולה יותר בטמפרטורה הגבוהה יותר.</li> <li style="text-align: right;">חוק בויל: אם נפח הגז מצטמצם, שטח דופן המיכל פוחת, ותדירות ההתנגשות של מולקולה-דופן עולה, שניהם מגבירים את הלחץ שמפעיל הגז.</li> <li style="text-align: right;">חוק אבוגדרו: בלחץ וטמפרטורה קבועים, התדירות והכוח של התנגשויות מולקולה-דופן קבועים. בתנאים כאלה, הגדלת מספר המולקולות הגזיות תדרוש גידול פרופורציונלי בנפח המיכל על מנת להניב ירידה במספר ההתנגשויות ליחידת שטח כדי לפצות על התדירות המוגברת של ההתנגשויות.</li> <li style="text-align: right;">חוק דלתון: בגלל המרחקים הגדולים ביניהם, המולקולות של גז אחד בתערובת מפגיזות את דפנות המיכל באותה תדירות, בין אם קיימים גזים אחרים או לא, והלחץ הכולל של תערובת גז שווה לסכום הלחצים (החלקיים) של הגזים הבודדים.</li> </ul> טקסט זה מותאם מ <a href="https://openstax.org/books/chemistry-2e/pages/9-5-the-kinetic-molecular-theory">Openstax, Chemistry 2e, Section 9.5: The Kinetic-Molecular Theory.</a></div>

המבחן של התיאוריה המולקולרית הקינטית (KMT) והנחות היסוד שלה הוא יכולתה להסביר ולתאר את התנהגותו של גז. חוקי הגז השונים ...

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KEY TERMS AND CONCEPTS

מונחים ומושגים מרכזיים

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

gas-pressure-patterns-in-kinetic-molecular-theory

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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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

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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...

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

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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...

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...

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...

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Gas Particle Motion, Diffusion, and Effusion

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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

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

Gas Pressure Patterns in Kinetic Molecular Theory | JoVE K12

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Classifying Matter by State

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Classifying Matter by Composition

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Physical and Chemical Properties of Matter

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Physical Properties of Matter

A physical property is ...

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Molecular Comparison of Gases, Liquids, and Solids

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Intermolecular vs Intramolecular Forces

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Intermolecular Forces

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Comparing Intermolecular Forces: Melting Point, Boiling Point, and Miscibility

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Surface Tension, Capillary Action, and Viscosity

Surface Tension
The various IMFs between identical molecules of a substance are examples of cohesive forces. The molecules within a liquid are surrounded ...

States of Matter and Phase Changes

The internal energy of a substance&#8212;the total kinetic energy of all its molecules and the potential energy of their associated forces&#8212;depends ...

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

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

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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.

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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

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Enthalpy

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Thermochemical Equations

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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
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Hess's Law

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Standard Enthalpy of Formation

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Enthalpies of Reaction

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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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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

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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 ...

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 ...

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

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 ...

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

Gas Pressure Patterns in Kinetic Molecular Theory

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