Demonstrate the relationship between kinetic energy and molecular speed. Most of the volume which a gas occupies is empty space. Our mission is to provide a free, worldclass education to anyone, anywhere. In this article let us discuss the kinetic theory of gases and the assumptions considered for the kinetic theory of. Ideal gas law and kinetic theory of gases chapter 20 entropy and the second law of thermodynamics now we to look at temperature, pressure, and internal energy in terms of the motion of molecules and atoms.
The kineticmolecular theory the basic assumptions of kineticmolecular theory are. The internal energy of an ideal monatomic gas like helium and neon is given by the kinetic energy and only depends on temperature. Kinetic molecular theory is useful in describing the properties of. So for a monatomic gas, the kinetic energy is the total energy. Collisions between molecules and with their container are perfectly elastic. Describes how and why real gases differ from ideal gases. Note 17 the kinetic theory of gases sections covered in the text. Kmt provides assumptions about molecule behavior that can be used both as the basis for other. The molecules are in constant, random motion and frequently collide. The model, called the kinetic theory of gases, assumes that the molecules are very small relative to the distance between molecules. Foundations of the hypothesis, pressure of gases, maxwells law, ideal and actual gases, molecular and atomic energy, molecular free paths, viscosity of gases, diffusin of gases and conduction of heat. The kinetic theory of gases introduction and summary previously the ideal gas law was discussed from an experimental point of view.
Table \\pageindex1\ postulates of the kinetic theory of gases. The ideal gas law and kinetic theory of gases chapter 14 the ideal gas law and kinetic theory of gases stt18. State the major concepts behind the kinetic molecular theory of gases. Kinetic theory and the states of matter the science. Distribution of molecular speeds in chapter, we discussed the properties of an ideal gas by using such macroscopic variables as pressure, volume, and temperature.
The molecular kinetic theory of gases the properties of a prefect ideal gas can be rationalized qualitatively in terms of a model in which the molecules of the gas are in continuous chaotic motion. Kinetic theory of gases supplementary notes instructor. Lectures on kinetic theory of gases and statistical physics oxford physics paper a1 alexander a. The average kinetic energy of molecules in a gas is proportional to the temperature. We will often refer to gases as consisting of particles and it. Basically, this kinetic theory allowed properties of gases at low pressures to be predicted, and it allowed an understanding of why some of the properties of real gases at higher pressures deviated from this ideal gas law. The molecules of a given gas are all identical but are different from those of another gas. For the love of physics walter lewin may 16, 2011 duration.
Kinetic theory of gases, a theory based on a simplified molecular or particle description of a gas, from which many gross properties of the gas can be derived. The relationship between pressure, density, and temperature was later found to have a basis in an atomic or molecular model of gases called the kinetic theory of gases that was developed by maxwell in the. Reif ends with a much wider ranging discussion of kinetic theory, transport and stochastic processes. Kinetic molecular theory can be used to explain both charles and boyles laws.
Over four hundred years, scientists including rudolf clausius and james clerk maxwell developed the kineticmolecular theory kmt of gases, which describes how molecule properties relate to the macroscopic behaviors of an ideal gasa theoretical gas that always obeys the ideal gas equation. He considered a gas to be a collection of molecules and made the following assumptions about these molecules. This booklet presents 45 worked examples on gas laws and kinetic theory, which is preceded by an introduction to the theory, laws and formulae associated with the topic. The kinetic theory of gases has developed a model which explains the behaviour of molecules, which should further explain the behaviour of an ideal gas. The kinetic molecular theory kmt is a simple microscopic model that effectively explains the gas laws described in previous modules of this chapter. Every gas consists of extremely small particles known as molecules. The kinetic theory assumes that collisions of gas particles are perfectly elastic. Here we see how the temperature and pressure of a gas arises from the average movement of its constituent atoms and molecules.
Thus, kinetic theory deals with the motion of the particles of matter. The british scientist james clerk maxwell and the austrian physicist ludwig boltzmann, in the 19th century, led in establishing the. Relate to the 1st law of thermodynamics thermal expansion cracking the nut. Kinetic molecular theory also known as particle theory states that all matter is made up particles and these particles are always in motion. The theory posits that gas pressure results from particles collisions with the walls of. Evaporation occurs when the fastest moving molecules escape from the surface of a liquid. The average kinetic energy of a collection of gas particles is directly proportional to absolute temperature only.
Note 17 the kinetic theory of gases university of toronto. Lecture 5 kinetic theory pennsylvania state university. Kinetic theory of gases explains the macroscopic properties of gases, such as pressure, temperature, viscosity, thermal conductivity, and volume, by considering their molecular composition and motion. But to study the action of the molecules, we must use a theoretical model. The kinetic molecular theory of gas part 1 youtube. The kinetic theory of gases, thermal physics from a. Gas phase quiz practice kinetic theory khan academy. At the triple point, all three phases are in equilibrium. In this model, the submicroscopic particles atoms or molecules that make up the gas are continually moving around in random motion, constantly colliding not only with each other but also with the sides of any container that the gas is. This proof was originally proposed by maxwell in 1860. Kinetic molecular theory and gas laws introduction to.
An ideal gas a gas that exactly follows the statements of the kinetic theory. Kinetic theory explains the behaviour of gases based on the idea that the gas consists of rapidly moving atoms or molecules. Gases were among the first substances studied using the modern scientific method, which was developed in the 1600s. Kinetic theory can explain the change of state by considering all matter substances to be made of particles. Postulate 1 zgases consist of discrete molecules that are relatively far apart. Apply the kinetic molecular theory to explain and predict the gas laws. Reviews kinetic energy and phases of matter, and explains the kineticmolecular theory of gases. The actual atomic theory got established more than 150 years later.
This is possible as the interatomic forces, which are short range forces that are important for solids and liquids, can be neglected for gases. New roman monotype sorts times arial wingdings symbol quill pen microsoft equation 3. Kinetic theory of gases this is a statistical treatment of the large ensemble of molecules that make up a gas. Kinetic molecular theory of gases introductory chemistry. Groth university of toronto institute for aerospace studies 4925 du. Pv nrt ideal gas law igl thus the kinetic theory describes the pressure of an ideal. The internal energy and change in internal energy only depends on the temperature change. Joule expansion and the earths atmosphere the starting point for the kinetic theory is the attempt to build a model for a gas based on the motions of individual atoms or molecules.
Schekochihiny the rudolf peierls centre for theoretical physics, university of oxford, oxford ox1 3np, uk merton college, oxford ox1 4jd, uk compiled on april 2020 these are the notes for my lectures on kinetic theory and statistical physics. Both huang and kardar treat kinetic theory and the boltzmann equation before they move onto statistical mechanics. Below the critical temperature, a gas can liquefy if the pressure is high enough. Kinetic theory of gases equation, assumption, concept. The molecules of a gas are identical spherical, rigid and perfectly elastic point masses. Kinetic molecular theory states that gas particles are in constant motion and exhibit perfectly elastic collisions. Limitations of kinetic theory the kinetic theory explains a lot of experimental data but there are still significant discrepancies for instance, the molar heat capacity of a gas can vary with tem perature. The model describes a gas as a large number of identical submicroscopic particles atoms or molecules, all of which are in constant, rapid, random motion. Ppt kinetic theory of gases powerpoint presentation. This new approach is the molecular approximation, which leads to gaskinetic theory. Introductory discussion of significant length dimensions. From the heat we can calculate the specific heat for various processes.
The microscopic theory of gas behavior based on molecular motion is called the kinetic theory of gases. Thermodynamics describes the equilibrium behavior of macroscopicbjects o. The aim of kinetic theory is to account for the properties of gases in terms of the forces between the molecules, assuming that their motions are described by the laws of mechanics usually classical newtonian mechanics, although quantum mechanics is. Lectures on kinetic theory of gases and statistical physics.
Multiplying the kinetic theory equation for pressure by v, the volume of the gas we obtain. The kinetic theory of gases provides methods for calculating lyapunov exponents and other quantities, such as kolmogorovsinai entropies, that characterize the chaotic behavior of hardball gases. Kinetic theory of gases university of california, berkeley. The kinetic theory of gases is a historically significant, but simple, model of the thermodynamic behavior of gases, with which many principal concepts of thermodynamics were established. We suppose that the internal motion of the atoms can be disregarded, and therefore, for this purpose, that the kinetic energy of the centerofmass motion is all the energy there is. Much of section 2 of these notes follows the path laid down in the these books. We can directly measure, or sense, the large scale action of the gas. Many gases deviate slightly from agreeing perfectly with the kinetic theory of gases. Lecture 14 ideal gas law and terms of the motion of. Kinetic theory states of matter, solids, liquids, gases. Looks at the kinetic theory of solids, liquids and gases, including changes of state.
728 179 86 629 337 1001 19 538 545 1146 421 1315 1087 1161 626 994 219 163 1529 1206 1086 1325 1308 444 518 1165 430 1085 1100 472 1248 794 1144 278 688