Kinetic theory


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Kinetic theory

  1. 1. Gases Part 1: Kinetic Molecular Theory
  2. 2. Kinetic Molecular Theory <ul><li>describes the behavior of gases in terms of particles in motion. </li></ul><ul><li>makes several assumptions about the </li></ul><ul><ul><li>size </li></ul></ul><ul><ul><li>motion, and </li></ul></ul><ul><ul><li>energy of gas particles. </li></ul></ul>
  3. 3. Assumptions <ul><li>Particle size </li></ul><ul><li>Particle motion </li></ul><ul><li>Particle energy </li></ul>
  4. 4. Particle Size <ul><li>Gases consist of small particles that are separated from one another by empty space. </li></ul><ul><li>The volume of the particles is small compared with the volume of the empty space. </li></ul>
  5. 5. Gas has Mass
  6. 6. Particle motion <ul><li>Gas particles are in constant, random motion. </li></ul><ul><li>Particles move in a straight line until they collide with other particles or with the walls of their container. </li></ul>
  7. 7. Elastic Collisions <ul><li>Collisions between gas particles are elastic. </li></ul><ul><li>An elastic collision is one in which no kinetic energy is lost. </li></ul>
  8. 8. Particles move very fast
  9. 9. Particle energy <ul><li>Kinetic energy is a function of the mass and speed of a particle. </li></ul><ul><li>In a sample of a single gas, all particles have the same mass but all particles do not have the same velocity. </li></ul><ul><li>Therefore, all particles do not have the same kinetic energy. </li></ul>
  10. 10. Kinetic Energy and Momentum
  11. 11. Properties of Gases <ul><li>Low density </li></ul><ul><li>Compressible </li></ul><ul><li>Diffuses </li></ul>
  12. 12. Low density <ul><li>Density – mass per unit of volume (g/cm 3 ) </li></ul><ul><li>Density of gasses is much lower than the density of solids or liquids. </li></ul>
  13. 13. Compressible <ul><li>Gasses can be compressed </li></ul><ul><li>Compression – can be pushed into a smaller volume </li></ul><ul><li>Expansion – can be pulled into a greater volume </li></ul>
  14. 14. Diffusion <ul><li>the movement of one material through another. </li></ul><ul><li>particles diffuse from an area of high concentration to one of low concentration </li></ul>
  15. 15. Temperature and Pressure <ul><li>Kinetic theory explains the temperature and pressure of gasses </li></ul><ul><ul><li>How fast the molecules of a gas are going </li></ul></ul><ul><ul><li>How heavy the molecules are </li></ul></ul>
  16. 16. Temperature <ul><li>Temperature is a measure of the average kinetic energy of the particles in a sample of matter. </li></ul>
  17. 17. In other words… <ul><li>Temperature is related to </li></ul><ul><ul><li>How fast the molecules of a gas are moving </li></ul></ul><ul><ul><li>How often the molecules hit the walls of the container </li></ul></ul>
  18. 18. Gas has temperature
  19. 19. Pressure <ul><li>defined as force per unit area. </li></ul><ul><li>Gas particles exert pressure when they collide with the walls of their container. </li></ul>
  20. 20. In other words… <ul><li>Pressure is related to </li></ul><ul><ul><li>How fast the molecules of a gas are moving </li></ul></ul><ul><ul><li>How much the particles weigh </li></ul></ul><ul><ul><li>How hard the molecules hit the walls of the container </li></ul></ul>
  21. 21. Gas has pressure
  22. 22. Measuring Pressure <ul><li>A barometer is an instrument used to measure atmospheric pressure. </li></ul><ul><li>A manometer is an instrument used to measure gas pressure in a closed container. </li></ul>
  23. 23. Pressure Units <ul><li>SI unit of pressure is the pascal (Pa). It is named for Blaise Pascal. </li></ul><ul><li>One pascal is equal to a force of one newton per square meter: 1 Pa= 1 N/m 2 . </li></ul>
  24. 24. Other Pressure Units <ul><li>engineers often report pressure as pounds per square inch (psi). </li></ul><ul><li>pressures measured by barometers and manometers can be reported in millimeters of mercury (mm Hg). </li></ul>
  25. 25. Air pressure <ul><li>At sea level, the average air pressure is 760 mm Hg when the temperature is 0°C. </li></ul><ul><li>Air pressure often is reported in a unit called an atmosphere (atm). One atmosphere is equal to 760 mm Hg or 760 torr or 101.3 kilopascals (kPa). </li></ul>
  26. 26. Temperature and Pressure <ul><li>Temperature and pressure are directly proportional </li></ul><ul><li>As one goes up, the other goes up </li></ul><ul><li>As one goes down, the other goes down </li></ul>
  27. 27. Temperature and Pressure
  28. 28. Temperature and volume
  29. 29. Volume and Pressure