Download Starch/Water Osmosis Investigation Starch/Water Osmosis

Name ____________________________________
Starch/Water Osmosis Investigation
The dialysis tube may, for the purpose of this experiment, be considered a single living cell in greatly
enlarged form. In your group of four, two of you should do part 1 while the other two do part 2. You
do NOT have enough time to each part separately. Share results with your lab group.
Part 1: Starch on the inside and water/iodine on the outside
1.
2.
3.
4.
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6.
7.
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9.
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11.
Collect a piece of dialysis tubing.
Take the tubing and rub one of the ends between your thumb and pointer finger until it
opens. Do this for the other end of the tubing as well.
Roll one end of the tubing down a couple times and secure with a green clamp. Make sure
it’s clamped tightly!!! (be sure to make sure as much air is out of the tube before
clamped)
Insert ~6mL of starch solution using the pipette (one full squeeze of the pipette will be
approximate 2mL) into the open end of the dialysis tube.
Roll and clamp the other end of the dialysis tubing.
Gently rinse any excess starch solution from the newly clamped dialysis tube.
Fill the beaker with ~150 mL of tap water. Add ~20 drops of Iodine solution to this water
and stir well. (Iodine will turn blue-black in the presence of starch).
Place the artificial cell (the dialysis tubing) into the beaker of solution and allow it to
remain undisturbed for at least 30 minutes.
After 30 minutes, record your qualitative observations in the table.
Clean all supplies with soap and water to get rid of any remains of starch and iodine.
Throw the used dialysis tubing away in the garbage.
Starch/Water Osmosis Investigation
The dialysis tube may, for the purpose of this experiment, be considered a single living cell in greatly
enlarged form. In your group of four, two of you should do part 1 while the other two do part 2. You
do NOT have enough time to each part separately. Share results with your lab group.
Part 2: Water/iodine on the inside and starch on the outside
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
Collect a piece of dialysis tubing.
Take the tubing and rub one of the ends between your thumb and pointer finger until it opens.
Do this for the other end of the tubing as well.
Roll one end of the tubing down a couple times and secure with a green clamp. Make sure it’s
clamped tightly!!!
Insert ~4mL of tap water using the pipette (one full squeeze of the pipette will be approximate
2mL) into the open end of the dialysis tube.
You also want to add ~20 drops of Iodine solution into dialysis tube along with the water.
(Iodine will turn blue-black in the presence of starch).
Roll and clamp the other end of the dialysis tubing. (be sure to make sure as much air is out of
the tube before clamped)
Gently rinse any excess solution from the newly clamped dialysis tube.
Fill the beaker with ~150 mL of starch solution.
Place the artificial cell (the dialysis tubing) into the beaker of solution and allow it to remain
undisturbed for at least 30 minutes.
After 30 minutes, record your qualitative observations in the table.
Clean all supplies with soap and water to get rid of any remains of starch and iodine.
Throw the used dialysis tubing away in the garbage.
Name ____________________________________
OSMOSIS: Starch / Water Lab
Overarching Question:
What substances can easily pass through the semipermeable membrane of a cell?
Background Information:
Dialysis tubing is a selectively permeable membrane. This will be used to model the plasma membrane that
surrounds all cells.
Iodine changes from orange to purple in the presence of starch. Iodine is added to the water so we can see
what substances can pass through the membrane. The color change of the iodine will let us know if the
water has moved. The color change will allow us to collect qualitative data. In previous transport
investigations we have collected quantitative data by finding the change in mass.
The starch solution contains more solute than the water solution.
Testable Question:
How does the concentration of starch (solute) drive osmosis (water movement)?
IV: placement of starch solution (Part 1: starch on inside of cell, Part 2: water on the inside of the cell)
DV: movement of substances
Hypothesis:
Evidence:
Cell Situation
Part 1:
Starch on the
inside of the cell
Part 2:
Water on the
inside of the cell
Claim:
Reasoning:
BEFORE
Qualitative Data
AFTER 30 MINUTES
Qualitative Data
What type of
solution is this?