Difference Between Particle Model of Matter and Kinetic Molecular Theory

Key Difference – Particle Model of Matter vs Kinetic Molecular Theory
 

Particle model of matter is a model that is used to explain the arrangement of atoms, molecules or ions which are present in any material. Kinetic molecular theory is a theory used to explain physical properties of a gas. The key difference between particle model of matter and kinetic molecular theory is that the particle model of matter describes the properties of solid, liquid and gas phases of matter whereas the kinetic molecular theory describes the properties of gases.

CONTENTS

1. Overview and Key Difference
2. What is Particle Model of Matter 
3. What is Kinetic Molecular Theory
4. Side by Side Comparison – Particle Model of Matter vs Kinetic Molecular Theory in Tabular Form
5. Summary

What is Particle Model of Matter?

Particle model of matter is a model that explains the arrangement of particles (atoms, molecules or ions) in a certain phase of matter. There are three main phases any matter can exist in: solid phase, liquid phase and gas phase. The particle model expresses the following concepts:

• All matter is built from small particles.
• These tiny particles are always in motion.
• There are empty spaces between these particles.
• When the matter is heated, the movement of particles increases.

Solid Phase

The solid phase is the phase of matter in which particles (atoms, molecules or ions that the solid is made of) are held tightly. Therefore, the particles are very closely packed. There are very tiny empty spaces between the particles. There are very strong intermolecular interactions between particles. These features give solids a particular shape. Since the particles are tightly packed, the particles show almost negligible movement (vibrations can be observed most of the times; hence particles remain in certain positions). As the solid gets a fixed shape, it has a fixed volume as well. The density of a solid is very high compared to liquids and gases.

Liquid Phase

The liquid phase is a phase of matter in which particles are packed closely together, but it is not a tight packing as in solids. The empty spaces between particles are large when compared to solids, but are small compared to gases. Particles can move freely. The liquid has no defined shape; it obtains the shape of the container in which the liquid is present. The density of a liquid is less than that of a solid and higher than that of a gas. However, a liquid has a fixed volume since the particles are packed closely together.

Gas Phase

The gas phase is a phase of matter in which particles are in continuous movement in random directions. Therefore, there are large spaces between gas particles. These particles fill up a closed container in which the gas is present. Then the gas obtains the volume of the container. The density of a gas is very less compared to that of solids and liquids.

What is Kinetic Molecular Theory?

Kinetic molecular theory is a theory that describes the physical properties of gases at their molecular level. The concepts of the kinetic molecular theory are as follows.

1. Gases contain particles that are in constant, random motion.
2. These particles collide with each other constantly. The collisions are completely elastic.
3. The volume of a gas molecule is negligible compared to the volume of the container in which the gas is present. But these particles have a considerable mass.
4. There are no intermolecular forces between gas molecules.
5. The average kinetic energy of the gas is proportional to the absolute temperature of the gas.

The relationship between the kinetic energy and speed of gas molecules can be given as below.

KE = ½.mv²

Where KE is the kinetic energy, m is the mass of a gas particle and v is the average velocity of gas molecules. But measuring these parameters is difficult; thus, the equation is modified as below.

KE = 3/2.k_BT

Where KE is the kinetic energy, k_B is the Boltzmann’s constant (1.381×10^-23 m² kg s^-2 K^-1), and T is the absolute temperature of the gas (in Kelvin units). This equation indicates that the kinetic energy of the gas is directly proportional to the absolute temperature of the gas.

What is the Difference Between Particle Model of Matter and Kinetic Molecular Theory?

Summary – Particle Model of Matter vs Kinetic Molecular Theory

The particle model and kinetic molecular theory explain different physical properties of matter. Particle model is the model that explains the arrangement of particles (atoms, molecules or ions) in a certain phase of matter. Kinetic molecular theory describes the relationship between kinetic energy and other properties of a gas. The key difference between particle model of matter and kinetic molecular theory is that the particle model of matter describes the properties of solid, liquid and gas phases of matter whereas the kinetic molecular theory describes the properties of gases.

Reference:

1. “Particle Model of Solids, Liquids and Gases.” Chemstuff, 8 June 2012, Available here.
2. Baker, Rhys. “What is the Particle Model – A Guide to Solids, Liquids and Gases.” Owlcation, Owlcation, 14 June 2016, Available here.
3. Libretexts. “Kinetic Molecular Theory of Gases.” Chemistry LibreTexts, Libretexts, 2 Oct. 2016, Available here.

Image Courtesy:

1. “States of matter En” By Yelod – Wikimedia Commons * Yelod – Wikipedia (En) * ילוד – ויקיפדיה העברית – Own work, (CC BY-SA 3.0) via Commons Wikimedia
2. “Kinetic theory of gases (2)” By Olivier Cleynen and User:Sharayanan – Own work based on File:Kinetic theory of gases.svg (CC BY-SA 3.0) via Commons Wikimedia