Experiment: Phase Change


    The JAVA applet below simulates the dynamics of phase change in a liquid-vapor system. Molecules of a pure substance in the vapor phase appear as light green or purple balls. The dark green or purple colored balls represent the molecules of the same substance in the lquid phase. Select the relative magnitude (weak or strong) of the intermolecular forces of attraction in the liquid phase and temperature (T1,T2, or T3). Click the "start" button to begin the animation. When the system achieves equilibrium, the animation will stop automatically. The average numbers of molecules in the vapor and liquid phases, the vapor pressure, and the temperature are displayed above the reaction container.

  1. Select "weak" for the intermolecular forces and temperature T1. Allow the system to achieve equilibrium. Briefly characterize the vapor and liquid phases.
  2. Select "weak" for the intermolecular forces and temperature T1. Allow the system to reach equilibrium. Briefly describe the process of phase change.
  3. Select "strong" for the intermolecular forces and allow the system to achieve equilibrium at temperature T1. Repeat the experiment with the temperature set at T2 and then T3. How does the average number of molecules in the vapor phase change with a change in the temperature and why?
  4. Determine the enthalpy of vaporization, DHvap, for the liquid with the"strong" intermolecular forces of attraction.
  5. Select temperature of T2 and allow the system to achieve equilibrium at each of the intermolecular forces of attraction (weak and strong). How does the vapor pressure change with a change in the magnitude of the intermolecular forces of attraction in the liquid phase and why?

    Include data from your experiments to support your answers to the questions.

Nutt 98




Dr. Nutt's CHE 115 Course