The Effect of the Type of Bag on
the Rate of Diffusion
Nick Gude
Period 3
M. Pietrangelo
Problem Statement and Hypothesis
• Which brand of bag will
have the slowest
diffusion rate?
• Will the results prove
significant enough to be
able to claim that that
brand(s) has the best
plastic content?
• If different brands of
bag are used then they
will have different
amounts of time for
diffusion to occur.
• Prediction
– Ziploc-Slowest Rate
– Giant-Normal Rate
– Hefty-Fastest Rate
Basic Concepts
• Diffusion: the primary method of short
distance transportion in a cell and cellular
systems; a cell’s means of transporting things
such as food to and from other cells (Ordom,
McCandless).
– Materials pass through pores in the membrane
from high to low concentration.
• Indicator: usually visual sign that change has
occurred in an experiment.
Design Diagram
• IV: Brand of Bag
Level
Ziploc
Hefty
Giant
Trials
10
10
10
• DV: How long (in minutes) it takes for the starch in
the bag to diffuse with the iodine solution outside.
• Constants: room temp., container size, plastic bag
size, amounts of iodine and starch solutions for each
trial.
• Materials: Ziploc, Giant, and Hefty bags, three glass
bowls, graduated cylinder, water, cornstarch, iodine,
transfer pipette, timer.
Design Diagram cont. (Procedure)
1. In each bowl: 1L of water + 20 ml of iodine.
2. In each bag: two tsp. starch and fill bag halfway
with water.
3. Put one of each brand with added ingredients
into its respective bowl.
4. Start timer and observe.
5. Once evidence of diffusion is seen (a purplishblack color), record the time for that trial in data
table.
6. Ten trials for each brand.
Results: Data
Levels
Ziploc
Giant
Hefty
Trial 1
Trial 2
Trial 3
Trial 4
Trial 5
Trial 6
Trial 7
Trial 8
Trial 9
Trial 10
Average
31.33m
31.38m
31.46m
30.95m
31.42m
31.4m
30.98m
31.5m
31.4m
31.35m
31.53m
20.33m
19.96m
17.55m
17.66m
18.08m
17.7m
20.2m
22.75m
20.16m
18.65m
19.5m
20.58m
20.5m
18.46m
19.25m
18.31m
17.18m
18.33m
18.93m
20.01m
19.13
19.12m
Diffused?
(Y/N)
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
Average Diffusion Rates
• Ziploc: Sum of all trial times divided by
number of trials (10) = 31m 32s avg.
• Giant: Sum of all trial times divided by number
of trials (10) = 19m 30s avg.
• Hefty: Sum of all trial times divided by number
of trials (10) = 10m 7s avg.
Graph of Diffusion Rate Averages
31m 32s
19m 30s
19m 7s
Statistical Analysis
• 2 Sample T-tests were used to determine if
the results of the experiment were significant.
• Ziploc T Tests to both Giant and Hefty both
resulted in low probability of chance (p <
p - value
.0001) Brand
Ziploc vs. Giant
1.06 X 10^-9 (zero)
Ziploc vs. Hefty
8.48 X 10^-12 (zero)
Hefty vs. Giant
.35 (could go either way)
• The results were significant, and it could be
claimed that Ziploc will always have a slower
diffusion rate than the other two.
Statistical Analysis cont.
• Based off the information gathered from the
results of the experiment, it is safe to say that
the original hypothesis that each bag would
have a different diffusion rate is rejected,
since although Ziploc’s time was proven to
always be slower, Giant and Hefty could go
either way.
Me with my materials, 11/4/10
Me starting the first trial, 11/13/10
Me holding up a diffused bag, 11/14/10
Results Explanation
• The diffusion rate is related to the number
and size of the pores in each bag brand.
• Ziploc had a slower diffusion rate, therefore
less or smaller pores in the plastic.
• Hefty and Giant had relatively equal diffusion
rates, therefore a relatively equal size and
amount of pores.
Sources of Error
• Not refilling the bowls with fresh iodine for
every trial could have slowed down the
diffusion time for a few trials.
• The bowls were not completely identical, and
this could have affected the diffusion rate.
• Iodine to size of bag ratio: experiments found
online used smaller, thinner sandwich bags,
which could have slowed down what would
have been the regular diffusion rate for the
bags.
Possible Improvements/Extentions
• For each trial, use a freshly mixed iodine and
water solution.
• Submerge each bag as much as possible,
perhaps get deeper containers.
• Using more iodine in the solution to
compensate for the type of bags used.
Applications
• Model/Simulation of simple cellular diffusion.
– Used by many schools already for exactly that
purpose.
• Could perhaps influence people’s decisions
about which brand of plastic bag is best,
maybe an indicator that Ziploc has better
quality plastic.
Acknowledgements/Thank You’s
• Parents
• Miss Pietrangelo
• The people who accepted my project
• And YOU