Chapter 10.1 The Kinetic-Molecular Theory

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Chapter 10.1 The Kinetic-Molecular Theory

  1. 1. Physical Characteristics of Gases<br />Chapter 10.1<br />The Kinetic – Molecular Theory of Matter <br />
  2. 2. Objectives:<br />State the kinetic-molecular theory of matter, and describe how it explains certain properties of matter.<br />List the five assumptions of the kinetic-molecular theory of gases. Define the terms ideal gas and real gas.<br />Describe each of the following characteristic properties of gases: expansion, density, fluidity, compressibility, diffusion, and effusion.<br />Describe the conditions under which a real gas deviates from “ideal” behavior.<br />
  3. 3. Kinetic-Molecular Theory (KMT)<br /><ul><li>·        </li></ul>Based on the idea that particles of matter are always in motion.<br />Provides a model of an ideal gas<br />Imaginary gas that perfectly fits all the assumptions of the kinetic-molecular theory.<br />KMT is based on the following 5 assumptions: <br />Gases consist of large numbers of particles that are far apart relative to their size.<br /><ul><li>Volume of gas particles occupy a volume usually about a thousand times greater than liquid and solid particles.</li></li></ul><li>Collisions between gas particles and between particles and container walls are elastic collisions.<br /><ul><li>Elastic collisions are ones in which there is no net loss of kinetic energy.</li></ul>Gas particles are in continuous, rapid, random motion. They therefore possess kinetic energy.<br /><ul><li>Kinetic energy is the energy of motion.</li></ul>Animation<br />Source:<br />www.chm.davidson.edu/ChemistryApplets/KineticMolecularTheory/BasicConcepts.html <br />
  4. 4. There are no forces of attraction or repulsion between gas particles.<br /><ul><li>Think of gas particles as small billiard balls, when they collide , they do not stick together, they bounce apart immediately.</li></ul>The average kinetic energy of gas particles depends on the temperature.<br /><ul><li>KE = ½ mv2
  5. 5. m is mass of particle
  6. 6. v is it’s speed
  7. 7. Higher the temperature, the faster the particles move</li></li></ul><li>Kinetic-molecular theory and the nature of gases<br />Expansion: <br /><ul><li>Gases do not have definite shape nor volume
  8. 8. The expand to fill container and take it’s shape and volume</li></ul>Kinetic-moleculartheory<br />Gas particles move rapidly in all directions (assumption 3) without significant attraction or repulsion between them ( assumption 4)<br />
  9. 9. Fluidity<br /><ul><li>Ability to flow
  10. 10. Liquids and gases are considered fluids because they both flow</li></ul>Kinetic-moleculartheory<br />Low Density<br /><ul><li>Density of a gas is 1/1000ththat of liquid or solids.</li></ul>Animation<br />Kinetic-moleculartheory<br />Particles are so much farther apart in a gaseous state (assumption 1).<br />
  11. 11. Compressibility<br /><ul><li>Crowding particles closer together.</li></ul>Kinetic-moleculartheory<br />Gas particles are initially far apart (assumption 1), allowing the particles to be crowded together.<br />Diffusion<br /><ul><li>Spontaneous mixing of the particles of two substances caused by their random motion.</li></ul>Kinetic-moleculartheory<br />Random and continuous motion of the molecules (assumption 3) carries them throughout the available space.<br />
  12. 12. Effusion<br /><ul><li>Process by which gas particles pass through a tiny opening.</li></ul>Animation of Effusion<br />Source:<br />http://www.chem.iastate.edu/group/Greenbowe/sections/projectfolder/flashfiles/gaslaw/micro_effusion.html<br />
  13. 13. Deviation of Real Gases from Ideal Behavior<br />Real Gas<br />Gas that does not behave completely according to the assumptions of the kinetic-molecular theory.<br />There are actually attractive forces between particles of gases, especially under higher pressures and lower temperature.<br /><ul><li>Kinetic-molecular theory
  14. 14. Most likely holds true for:
  15. 15. Particles that have little attraction
  16. 16. Ex: He, Ne ( monatomic and nonpolar)
  17. 17. Ex: N2, H2 ( diatomic and nonpolar)
  18. 18. Gases more likely to deviate from ideal gas behavior
  19. 19. Ex: NH3, H2O (Polar molecules) stronger attractions</li>

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