Question

Student Exploration Gizmo: Diffusion

1. 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.

Variable	Set Up A	Set Up B
Wall
x in A
y in B
Temp
Particle mass

2. 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.

Trial	Set-up A Time to reach equilibrium	Set-up B Time to reach equilibrium
1
2
3
4

3. Calculate: Find the average time to reach equilibrium for each experiment:

1. Average time to reach equilibrium for set-up A: ____________

Average time to reach equilibrium for set-up B: ____________

4. Draw conclusions: Compare the average times to reach equilibrium for each set-up.

1. How did the variable you investigated affect the rate of diffusion? _________________

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2. Why do you think this was the case? ______________________________________

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5. 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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Answer 1

1. Diffusion Gizmo: It is a chamber that contain particle (here x any y are the particles) in the region A and B seperated by an opening. One can manipulate size of the opening, the concentrations of each particle, the temperature, and the particle mass so to determine the effect of these on the rate of diffussion. The experimental set up are as follows (only one variable needs to be manipulated):

Variable	Set up A	Set up B
Wall	25%	85%
x in A	100	0
y in B	100	0
Temp.	100K	100K
particle mass	15 amu	15 amu

Let say the time equibrillium will be-

Trial	Sey up A	Set up B
	Time to reach equilibrium	Time to reach equilibrium
1	98	388
2	64	590
3	68	355
4	52	472

A. Average will be calculated as the sum of all trials divided by total number of trials. So,

1. Average time to reach equilibrium for set-up A: 282/4 = 70.5
2. Average time to reach equilibrium for set-up B: 1805/4 = 451.2

4. A. The variable you investigated affect the rate of diffusion : The one with wall 84%, region A took more time to diffuse with region B.

A. Why do you think this was the case? Since the wall is thick (85%), thus it prevent the particle in A to move towards B.

5. On your own: Investigate the remaining variables: Since the diffusion is depend upon the size, concentration, temp and particle mass. So, manipulation in any of the variable affect the rate of diffussion.