Diffusion and Osmosis Lab
Ariana Murphy
Cam Dwyer, Maggie Bulger, Anabella Driscoll
Mr. Rowell
January 27, 2020
Abstract:
In this lab students tested three different hypothesis.In the first the students
tested the diffusion of deionized water into a glucose starch solution filled dialysis bag in
order to understand the concept of diffusion. The second experiment consisted of the
students weighing deionized water filled dialysis bags before and after placing them
inside of sucrose solution filled cups in order to better understand osmosis. The final
experiment was based off of water potential where the students weighed potatoes and
placed them in a sucrose solution to determine which had a higher and lower water
potential.
Introduction:
The membrane around a cell helps to protect the internal parts of the cell
due to its semipermeable traits. A semipermeable membrane only allows certain
molecules to pass through using facilitated diffusion and active transport. Diffusion is the
net movement of a substance from a higher concentration to a lower concentration.This
occurs because molecules in solutions or cells are constantly moving and collide with
each other, when they collide some molecules will move to a lower concentrated area in
order to reach an equilibrium. Even after they reach an equilibrium the molecules will
remain moving. This lab’s purpose is to observe, measure, and compare the diffusion of
water, starch and glucose through both artificial and natural membranes. After the
completion of this lab students will be able to measure a solution’s water potential in a
controlled experiment. In order to determine solute potential the student will use the
following equation: ΨS = -iCRT. The student will become familiar with the concepts of
concentration gradient, osmosis, selectively permeable membrane, diffusion, and
plasmolysis.
Hypothesis:
Activity 1: If a dialysis bag filled with15mL of a glucose-starch solution is placed
inside of a 9 oz cup filled with deionized water then diffusion will occur and iodine will
seep through the bag’s semipermeable membrane.
Activity 2: If different moles of sucrose solution are put into six different cups and
deionized water filled dialysis bags are placed into the cups then the mass of the bag
will increase more in the higher concentrated cups than in the lower sucrose solution
concentrations.
Activity 3: If four potato slices are placed in cups of differently concentrated
sucrose solution filled cups then the potatoes’ mass will decrease overnight.
Materials & Procedures:
Activity 1:
●
15% Glucose- 1% Starch solution, 16mL
●
Iodine solution, 4mL
●
Water, deionized, 100mL
●
Cup, plastic, 9 oz.
●
Dialysis tubing, presoaked, 20cm
●
Dialysis tubing clamps, disposable, 2
●
Funnel, plastic
●
Glucose test strips,4
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Graduated cylinder, 25-mL
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Marker or wax pencil
●
Paper, white
●
Pipet, graduated,6
●
Weighing dish, small
Activity 1 Procedure:
1.
Obtain 1ml of the glucose-starch solution in a graduated pipet.
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- Fall '19
- Osmosis, Semipermeable membrane, bag
