Gas Phase Boltzman Distribution

At any set temperature, the molecules in any large sample have a variety of energies. While some have low kinetic energy, others have relatively high kinetic energy. These energies are a function of the velocities of the individual molecules, which depend on both the molecular masses of the molecules and the temperature of the sample. The distribution of velocities, and therefore energies, is referred to as a Boltzmann distribution, named after Ludwig Boltzmann, an Australian mathematician and physicist who worked largely in part on the kinetic theory of gases.

A plot of the number of moving molecules moving at a certain velocity vs. that velocity is called a Boltzmann plot. This module illustrates the kinetic energy distribution of molecules in the gaseous state. Boltzmann plots illustrate the relationship of the number of molecules and velocity for six gases at varying temperatures.

INSTRUCTIONS

1. Select the gas by clicking on one of the Gases option buttons. The molecular mass of the gases is also included with each gas option. Each plot is displayed in the same color as the option button for the gas of interest.
2. Select a temperature by adjusting the Temperature scroll bar, which adjusts the temperature between 200. and 600. K.
3. Click on the Calculate button to generate the distribution plot.

Multiple plots may be put on the screen at any time and the Clear Plot button can be used to clear the plot area. When looking at the effects of temperature on velocity in the Boltzmann distribution, it is useful to have a point of reference for comparison. In this program a line marks a velocity of 1000. m/s, and reports the percentage of molecules in the set sample that move faster than 1000. m/s.
Last modified: April 13, 2000