This model is used to describe the behavior of gases. More specifically, it is used to explain macroscopic properties of a gas, such as pressure and temperature, in terms of its microscopic components, such as atoms.
Skills to Develop To understand the significance of the kinetic molecular theory of gases. The laws that describe the behavior of gases were well established long before anyone had developed a coherent model of the properties of gases. In this section, we introduce a theory that describes why gases behave the way they do.
The theory we introduce can also be used to derive laws such as the ideal gas law from fundamental principles and the properties of individual particles. A Molecular Description The kinetic molecular theory of gases explains the laws that describe the behavior of gases.
Developed during the midth century by several physicists, including the Austrian Ludwig Boltzmann —the German Rudolf Clausius —and the Englishman James Clerk Maxwell —who is also known for his contributions to electricity and magnetism, this theory is based on the properties of individual particles as defined for an ideal gas and the fundamental concepts of physics.
Thus the kinetic molecular theory of gases provides a molecular explanation for observations that led to the development of the ideal gas law. The kinetic molecular theory of gases is based on the following five postulates: A gas is composed of a large number of particles called molecules whether monatomic or polyatomic that are in constant random motion.
Because the distance between gas molecules is much greater than the size of the molecules, the volume of the molecules is negligible. Intermolecular interactions, whether repulsive or attractive, are so weak that they are also negligible.
Gas molecules collide with one another and with the walls of the container, but these collisions are perfectly elastic; that is, they do not change the average kinetic energy of the molecules.
The average kinetic energy of the molecules of any gas depends on only the temperature, and at a given temperature, all gaseous molecules have exactly the same average kinetic energy. Molecules of a gas are in constant motion and collide with one another and with the container wall.
Use the kinetic molecular theory of gases to describe how a decrease in volume produces an increase in pressure at constant temperature. Similarly, explain how a decrease in temperature leads to a decrease in volume at constant pressure. The kinetic theory of gases serves to explain temperature and pressure on the microscopic level. While it does not hold true for real gases, it is a good model for an ideal gas. Real gases exert force upon one another, and their particles have a4/4(4). The behavior of ideal gases is explained by the kinetic molecular theory of gases. Molecular motion, which leads to collisions between molecules and the container walls, explains pressure, and the large intermolecular distances in gases explain their high compressibility.
Although the molecules of real gases have nonzero volumes and exert both attractive and repulsive forces on one another, for the moment we will focus on how the kinetic molecular theory of gases relates to the properties of gases we have been discussing.
Postulates 1 and 4 state that gas molecules are in constant motion and collide frequently with the walls of their containers.
The collision of molecules with their container walls results in a momentum transfer impulse from molecules to the walls Figure 6. Since the collisions are elastic, the molecule bounces back with the same velocity in the opposite direction.
The exact expression for pressure is given as: This is the essence of the ideal gas law, which treats all gases as collections of particles that are identical in all respects except mass.
Postulate 2 also explains why it is relatively easy to compress a gas; you simply decrease the distance between the gas molecules. Postulate 5 provides a molecular explanation for the temperature of a gas. At a given temperature, heavier gas molecules have slower speeds than do lighter ones.
The distinction is important, however, because the rms speed is the speed of a gas particle that has average kinetic energy. Particles of different gases at the same temperature have the same average kinetic energy, not the same average speed. In contrast, the most probable speed vp is the speed at which the greatest number of particles is moving.
If the average kinetic energy of the particles of a gas increases linearly with increasing temperature, then Equation 6. At higher temperatures, therefore, the molecules of a gas move more rapidly than at lower temperatures, and vp increases.The Kinetic-Molecular Theory Explains the Behavior of Gases, Part II According to Graham’s law, the molecules of a gas are in rapid motion and the molecules themselves are small.
The average distance between the molecules of a gas is large compared to the size of the molecules. 7 An ideal and a rea l gas Each of these lines (isotherms) represents the behaviour of a gas at one specific plombier-nemours.comLAR KINETIC THEORY A cylinder contains dry air at a temperature of K.
Write down where the main assumptions of the kinetic theory are used kg m. Conceptual Kinetic Theory Objectives • Describe how the kinetic-molecular theory is used to explain how gases behave at different temperatures.
(Exploration 1) • Analyze data that shows how gas particle mass affects that gas’s behavior. (Exploration 2) • Describe the Maxwell-Boltzmann Distribution. (Explorations 1 and 2) Description of Activity The kinetic-molecular theory .
At any given temperature, the molecules of all gases have the same average kinetic energy. In other words, if I have two gas samples, both at the same temperature, then the average kinetic energy for the collection of gas molecules in one sample is equal to the average kinetic energy for the collection of gas molecules in the other sample.
Ix at molar mass of mercury = plombier-nemours.comLAR KINETIC THEORY 2 a 1a I.. explain how the r.0 mol of helium at a temperature of 27 QC.m. 2 Nmu F= _ _x_ Support your answ er with a calculation.
on the With reference to the appropriate physical principles.s. t. respectively. between collisions with the shaded face is t= (ii) The pressure increases if. Conceptual Kinetic Theory Objectives • Describe how the kinetic-molecular theory is used to explain how gases behave at different temperatures.
(Exploration 1) • Analyze data that shows how gas particle mass affects that gas’s behavior. (Exploration 2) • Describe the Maxwell-Boltzmann Distribution.