Содержание
- 2. Lecture 5 MOLECULAR-KINETIC THEORY OF IDEAL GASES THE MOLECULAR BASIS OF THERMAL PHYSICS EVAPORATION AND BOILING
- 3. Main assumptions for Ideal Gas Model The number of molecules in the gas is large, and
- 4. MOLECULAR-KINETIC THEORY OF IDEAL GASES An ideal gas is in a cubical container with sides of
- 5. The change of the i-th molecule momentum after collision is: Then the short-term force acting on
- 6. Using previous expressions we can find x-component of the long-term average force exerted by the wall
- 8. N is the number of molecules This result indicates that the pressure of a gas is
- 9. Molecular interpretation of temperature So we have Experimentally found the equation of state for an ideal
- 10. Theorem of equipartition of energy We can transform the last expression into Generalization of this result
- 11. Root-mean square speed of molecules Using the equation of state for an Ideal gas here n
- 12. Internal Energy In the molecular-kinetic model internal energy of a gas equals the sum of kinetic
- 13. Equation of State for an Ideal Gas Found experimentally: n is the number of moles of
- 14. The Boltzmann Distribution Law We found average kinetic energy of a molecule. But all molecules move
- 15. The Boltzmann Distribution Law Where n0 is defined such that n0dE is the number of molecules
- 16. Maxwell–Boltzmann speed distribution function If N is the total number of molecules, then the number of
- 17. Maxwell–Boltzmann speed distribution function dN = NV dV.
- 18. Gas molecules velocities Root mean square Mean Most probable
- 19. Evaporation We know that liquids evaporate when they’re below boiling temperature. The speed distribution curve for
- 20. . In order to evaporate, a mass of water must collect the large heat of vaporization,
- 21. Saturation Vapor Pressure Ordinary evaporation is a surface phenomenon - some molecules have enough kinetic energy
- 22. The process of evaporation in a closed container will proceed until there are as many molecules
- 23. Evaporation vs Boiling Ordinary evaporation is a surface phenomenon - since the vapor pressure is low
- 24. Boiling Point The boiling point is defined as the temperature at which the saturated pressure of
- 25. Collisions is the collision cross section. Then the volume it sweeps is . So this molecule
- 26. Then we can find mean collision time Considering movement of the target molecules: N is the
- 27. Mean free path is an average distance between collisions:
- 28. Tortuous path of a gas molecule A randomly moving molecule has such displacement: The displacement of
- 29. Transport Phenomena By means of collisions that molecules can carry physical properties (momentum, energy, concentration, etc.)
- 30. Some terms The critical temperature of a gas is that temperature above which the gas will
- 31. Van der Waals Gas n is the number of moles of the gas Term represents long-range
- 34. Скачать презентацию