CH 14 - Copyright 2010 TOUPADAKIS CHEMISTRY READER 2A...

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Copyright 2010 TOUPADAKIS CHEMISTRY READER 2A CHAPTER 14 1 Chapter 14 Kinetic-Molecular Theory of Gases 14-1 The Qualitative Kinetic Model of Gases 14-2 The Quantitative Kinetic Model of Gases 14-3 Types of Average Speed 14-4 The Meaning of Temperature 14-5 Diffusion and Effusion 14-6 Real Gases
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Copyright 2010 TOUPADAKIS CHEMISTRY READER 2A CHAPTER 14 2 About a couple of hundred years ago some people started to fly using hot air balloons. This different way of transportation demanded more understanding about the response of gases to changes of pressure and temperature. The need for more knowledge on the behavior of gases stimulated a lot of experiments. The early experimental observations that: V = k/P V = k•T V = k•n led to the formulation of the empirical law: PV = nRT But no one could give an explanation why the volume of a gas is reversely proportional to its pressure, directly proportional to its absolute temperature and also directly proportional to the number of its particles. The explanation was given only after the gas was considered to be consisted of a number of atoms or molecules moving chaotically in all directions away from each other. This consideration or the way of view of a gas is called the Kinetic- Molecular theory of Gases . Based on this view, called kinetic model, and by using a number of assumptions, laws of physics and math reasoning, scientists were able to give satisfactory explanation of the behavior of gases. For example they could explain why the pressure of a gas increases by decreasing its volume and increasing its temperature. 14-1 The Qualitative Kinetic Model of Gases Science initially proposes a qualitative model and later it expresses it mathematically. The qualitative kinetic model of gases is based on several assumptions. 1) Any sample of gas is made of a great number of molecules or atoms. 2) The m olecules or atoms are considered “point masses” i.e. they have mass but no volume. 3) The particles of the gas are in ceaseless random motion.
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Copyright 2010 TOUPADAKIS CHEMISTRY READER 2A CHAPTER 14 3 4) The molecules do not interact, in other words there are not attractive or repulsive forces between them. 5) When the particles of the gas collide, kinetic energy transfers from particle to particle but it is not changed to other forms of energy (elastic collisions). 14-2 The Quantitative Kinetic Model of Gases When the qualitative kinetic model of gases is expressed with a mathematical equation we obtain the quantitative kinetic model of gases. Each collision of an atom or molecule on the walls of its container gives rise to a brief force on the walls. But as billions of collisions take place every moment, the walls experience a constant force, and hence the gas exerts a steady pressure on the walls of the container where it is contained. Based on the previous assumptions and using laws of physics we can prove that:
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This note was uploaded on 04/22/2011 for the course CHEM 2A taught by Professor Guo during the Fall '08 term at UC Davis.

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CH 14 - Copyright 2010 TOUPADAKIS CHEMISTRY READER 2A...

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