Diffusion
Diffusion
Pre-Lab Questions
A concentration gradient affects the direction that solutes diffuse. Describe how molecules move with respect to concentration.
How does the size of a solute affect the rate of diffusion? Consider the size and shape of a molecule in your response.
Does polarity affect the rate of diffusion? Explain your answer using scientific principles.
Experiment 1: Diffusion Through A Liquid
Result Tables
Table 1: Rate of Diffusion in Corn Syrup
Time (sec)
Diffusion of Blue Dye (mm)
Diffusion of Red Dye (mm)
10
20
30
40
50
60
70
80
90
100
110
120
Table 2: Speed of Diffusion of Different Molecular Weight Dyes
Dye
Molecular Weight
Total Distance Traveled (mm)
Speed of Diffusion (mm/hr)*
Blue Dye
Red Dye
*Multiply the total distance diffused by 30 to get the hourly diffusion rate.
Post-Lab Questions
Record your hypothesis from Step 3 here. Be sure to support your hypothesis with evidence.
Which dye diffused the fastest?
Does the rate of diffusion correspond with the molecular weight of the dye?
Does the rate of diffusion change over time? Why or why not?
Examine the graph below. Does it match the data you recorded in Table 2? Explain why or why not. Submit your own plot if necessary.
Experiment 2: Concentration Gradients and Membrane Permeability
Result Tables
Table 3: Indicator Reagent Data
Indicator
Starch Positive Control (Color)
Starch Negative Control (Color)
Glucose Positive Control (Color)
Glucose Negative Control (Color)
IKI Solution
n/a
n/a
Glucose Test Strip
n/a
n/a
Table 4: Diffusion of Starch and Glucose Over Time
Indicator
Dialysis Bag After 1 Hour
Beaker Water After 1 Hour
IKI Solution
Glucose Test Strip
Post-Lab Questions
Why is it necessary to have positive and negative controls in this experiment?
Draw a diagram of the experimental set-up. Use arrows to depict the movement of each substance in the dialysis bag and the beaker.
Which substance(s) crossed the dialysis membrane? Support your response with data-based evidence.
Which molecules remained inside of the dialysis bag?
Did all of the molecules diffuse out of the bag into the beaker? Why or why not?
©eScience Labs, 2018
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