Student Exploration: Diffusion (solution)

Student Exploration: Diffusion 
Gizmo Warm-up Smells are carried by tiny particles that move through the air.
The Diffusion Gizmo™ shows gas particles in a chamber that is divided into two regions by a partial wall. Click Play ( ) and observe.
1. Describe the motion of the gas particles
2. Over time, what is happening?
3. Select the BAR CHART tab, and observe the chart for a few minutes. After the first 30 seconds or so, how much do the numbers of particles in each region change
4. Click Pause ( ), and select the GRAPH tab. What does the graph tell you about the number of particles in region A?
Question: How does temperature affect the rate of diffusion?
1. Observe : Set the temperature ( Temp. ) to 100 K, and press Play . Observe the motion of particles. Click Reset . Then set the temperature to 600 K, click Play , and observe.
How does the temperature of the gas relate to the motion of the particles?
2. Form hypothesis : How do you think temperature will affect the rate of diffusion?
3. Experiment : Click Reset . Set the Wall to 50%, x in A to 100, y in B to 0, Temp. to 100 K, and Particle mass to 15 amu (atomic mass units). Select the TABLE tab. Press Play . Click Pause when x in A first reaches 55% or below. Record this Time to reach equilibrium in the left table below. Repeat four more times at 100 K, and then run five trials with the temperature set to 600 K.
Activity A
4. Calculate : Find the average time to reach equilibrium for each experiment:
A. Average time to reach equilibrium at 100 K:
B. Average time to reach equilibrium at 600 K
5. Draw conclusions : Compare the average times to reach equilibrium for each temperature.
A. How did temperature affect the rate of diffusion?
B. Why do you think this was the case?
6. Extend your thinking : Why do you think the experimental results were different for each trial?
7. On your own : In our lives, we rarely experience temperatures that are above 373 K (100 °C) or below 273 K (0 °C). Investigate how much diffusion rates differ between these two temperatures. Describe the results of your experiments below
Introduction: The Diffusion Gizmo allows you to manipulate five variables: the Wall , the number of x particles in region A , the number of y particles in region B , the temperature, and the Particle mass .
Question: How do factors other than temperature affect the rate of diffusion?
1. Choose a variable : Pick a variable to investigate. Which one did you choose?
2. Form hypothesis : How do you think this variable will affect rates of diffusion?
3. Set up experiment : In a controlled experiment , only one variable is manipulated, or changed. Set up your experiment so that there is just one difference between set-up A and set-up B. List the Gizmo settings you will use for each set-up below
4. Gather data : Use the Gizmo to fill in each table. As before, the “time to reach equilibrium” is the time it takes for the number of x particles in region A to reach 55% or lower
Activity B 5. Calculate : Find the average time to reach equilibrium for each experiment
A. Average time to reach equilibrium for set-up
B. Average time to reach equilibrium for set-up
6. Draw conclusions : Compare the average times to reach equilibrium for each set-up. A. How did the variable you investigated affect the rate of diffusion?
B. Why do you think this was the case?
7. On your own : Investigate the remaining variables. Record all experimental results in your notes. Summarize your findings in the space below

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