Diffusion and
Osmosis
LNL #4
Getting Started
 Read
through the entire experiment
so you will know what is coming up
next.
 Write your hypothesis using the “IfThen” format. Each experiment
will have its own hypothesis.
 Follow the procedure, recording all
data. (That means write it all down in
an orderly way.)
Hypothesis

Before you can write the hypothesis, you need to
understand the purpose of the experiment. What
are you trying to ‘prove’ or find out by doing the
experiment? Where do you go for ideas about the
purpose of the experiment?
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What is the title of the experiment?
What are the objectives/goals of the experiment?
What is in the background information/introductory
paragraph that will help you?
Procedures
 Read
the Background section very carefully.
 Procedures can be re-written or copied and
pasted into the blank lab report.
 There are 5 experiments to complete.
 Experiments #1 and 2 are to show diffusion
occurring by watching color changes
Procedures (con’t)
 Experiment
#3 you will monitor the rate of
diffusion of acetic acid through the dialysis
membrane by measuring the change of the
pH of the solution in the beaker over time.
The concentration of the acetic acid is
decreased with each trial. The solution will
become more acidic as diffusion occurs.
A pH of 7 is neutral. A pH below 7 is acidic
; the lower the pH, the more acidic the
solution.
Procedures (con’t)

Experiment #4 You will use the same method as
before for determining the rate of diffusion, using a
pH meter to monitor the change of the pH of the
solution in the beaker, only this time you will use
acids with different size molecules. Smaller
molecules will pass through the membrane
more easily. The higher the molecular weight,
the bigger the molecule. In this experiment you
will attempt to determine the relationship of
between molecular weight and the rate of
diffusion.
Procedures (con’t)

Experiment # 5 you will confirm both the impermeability
of the dialysis membrane to albumin as well as the
movement of water across the membrane. Osmosis
is the transfer of water across a semi-permeable
membrane. The dialysis tubing used in these
experiments allows water molecules to pass through it,
but not the egg albumin. So the albumin in solution is
trapped on either side of the membrane. An imbalance
in the concentration of albumin on the two sides of the
membrane creates pressure that forces water to move
across the membrane.
Data/Observations
In
Experiments #1 and 2, answer
the questions.
In Experiments #3 and 4,
complete the tables.
In Experiment #5, answer the
questions.
Calculations/Interpretations
 There
are no calculations in this lab.
 Answer the questions in each
section of the lab report based on
the data (information) collected in
the experiments.
 The Background information may be
helpful in answering the questions.
Finishing Up
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Use the template to write your report.
Type your hypothesis immediately after the
directions for it.
Type (or copy and paste) your procedure
immediately following the directions for it.
Answer all of the questions in the
calculations/interpretations section.
Write your conclusion telling if your hypothesis
was correct or incorrect and support your
statement with your results. This should be about
a paragraph in length.