Gas Phase Boltzmann 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.
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INSTRUCTIONS
- 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.
- Select a temperature by adjusting the Temperature scroll bar, which adjusts the
temperature between 200. and 600. K.
- 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.
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