Get the Gizmo ready:
Select Hydrogen gas.
Set the Temperature to 300 K.
Introduction: The graph on the right side of the Gizmo represents the Maxwell-Boltzmann
distribution of particle velocities. The curve represents the probability of a particle moving at
the velocity shown on the x-axis of the graph. The higher the curve, the greater the probability of
finding a particle moving at that velocity will be.
Question: How are particle velocities distributed?
1. Observe: Move the Temperature slider back and forth. This time focus on the graph at right.
What do you notice about the shape of the graph? _________________________________
2. Analyze: Look at the left side of the graph as you raise the temperature from 50 to 1,000 K.
A. Even at the highest temperatures, are there still a few slow particles? ____________
B. At what temperature do you see the widest variety of particle velocities? __________
C. In general, is the Maxwell-Boltzmann curve a symmetrical or an asymmetrical curve?
3. Estimate: Because particles have a range of velocities at any given temperature, it is useful
to calculate the average velocity. Physicists express the average velocity in three ways:
most probable velocity (v
), mean velocity ( ), and root mean square velocity (v
Set the temperature to 200 K (the selected gas should still be Hydrogen).
A. Estimate the most probable velocity by looking at the peak of the curve. What is your
B. Turn on Show most probable velocity. What is the actual value? ______________
C. Base on the shape of the curve, do you think most of the particles are moving faster
or slower than the most probable velocity? ______________
(Activity B continued on next page)
When the temperature is low and colder the graph has a high peak and doesn't
stretch out in length very much. When the temperature is high and hotter the graph
has a low stretched line that exceed very high.
faster but somewhat
slowly at the same time