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Collin College BIOL 1408 Unit 7 Diffusion and Osmosis Packet
- Course
- BIOL 1408
- Institution
- Collin College
Collin College BIOL 1408 Unit 7 Diffusion and Osmosis Packet
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Unit 7Diffusion & Osmosis
This lab uses the following hazardous chemicals:
I. Barium Chloride
II. Benedict’s Indicator Reagent
III. Biuret Indicator Reagent
IV. Lugol’s Iodine Solution
V. Silver Nitrate
As a result students are required to wear, at minimum, Goggles & Gloves.
Abstract
This lab is composed of instructor demonstrations as well as student run experiments
meant to demonstrate the various principles regarding osmosis and diffusion. For the
instructor demonstrations, you will participate in a discussion that covers the concepts
critical to understanding the demonstration, and formulate a hypothesis derived from
the discussion. You will also utilize common laboratory techniques to explore the effect
of solute concentration on the rate of osmosis. Finally, you will look at selective
permeability of membranes using five different solutions and determining which
solution contained substances that were able to diffuse across the membrane.
7.1 The effect of size and temperature on diffusion
Your instructor will place two diffusion plates, each one with two holes punched in it, at
different temperatures. Each diffusion plate will contain a drop of potassium
permanganate (294 Daltons) and a drop of Janus Green (511 Daltons). Immediately after
adding the drops, the instructor will measure the diameter of the dye on the plates. One of
the two plates will be placed in the 37°C incubator, and the other will be placed at room
temperature. At the end of the thirty-minute incubation, the instructor will again measure
the diameter of each dye.
Note
The hypothesis for section 7.1 does not need to be written until after your
instructor has led the discussion on the effects of size and temperature on
diffusion. All other hypotheses in this unit should be written before coming
into lab.
91
, Hypotheses
Temperature’s effect on diffusion:
Having discussed the diffusion and the effect that temperature has on the
speed at which molecules move, I expect that after thirty minutes the
diameter of the diffused dye ring will be the greatest on the plate that is
placed at the temperature of ______________ because ________________
_________________________________________________________________
_________________________________________________________________
_________________________________________________________________.
The effect of molecular mass on diffusion:
Furthermore, having discussed the porous properties of agar and the effect
that these properties have on molecules of varying sizes and mass, I expect
that the diameter of ______________ will be larger than _______________ at
the thirty-minute time point because___________________________________
____________________________________________________________________
____________________________________________________________________.
Results
Potassium Potassium
Janus Green Janus Green
Permanganate Permanganate
RT 37 °C
RT 37 °C
Time
Distance (cm) Distance (cm) Distance (cm) Distance (cm)
(Minutes)
0
30
Figure
1.
Measurement
of
Diameters
of
Janus
Green
and
Potassium
Permanganate
at
different
temperatures.
Conclusions
Evaluate your results recorded in the table above. What did you see? Compare your
actual results to the hypotheses that you wrote after your class discussion. How do the
results compare to each of your two hypotheses? What did you learn? Write out your
conclusions in the space provided.
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