Name:______________________
Class: ______
Date: ______
Background Information:
You have learned that osmosis and diffusion are ways in which the cell moves materials
across the cell membrane. Osmosis is the diffusion of water across the cell membrane.
Neither of these processes requires energy (passive transport). If the cell takes in a lot of
water, it becomes rigid and stiff. When cells lose water, the cell becomes shriveled. This
happens when a plant wilts, or when a grape turns into a raisin.
Question: How will salt water and tap water affect a potato?
Concepts:
Osmosis:______________________________________________________________
Passive Transport:_______________________________________________________
Rigid and Stiff Cell:______________________________________________________
Shriveled or Wilting Cell:__________________________________________________
Materials:
Salt water
Tap water
3 cups
Gummy Bears
Potato pieces (3)
Ruler
Paper Towel
Gummy Bears
Procedure:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
Label two cups A =TAP and B =SALT.
Fill cup A half way with cool tap water.
Fill cup B half way with SALT water.
Obtain 3 pieces of potato that are about the same size.
Using a ruler, measure the length, in millimeters, of all 3 pieces of potato and record in the DATA
chart below. (For example, 10 mm)
Place potato #1 in a damp paper towel.
Place potato #2 into cup A.
Place potato #3 into cup B.
Let the pieces of potato sit for 15 minutes. Record start time so you know when to take potatoes
out of their “treatments.” Start Time ______________________
While you are waiting, start PART 2 (Gummy Bear section).
After the 15 minutes is up, remove the potatoes from their treatments and re-measure their
lengths and make observations about their appearance.
Throw away the potato pieces, return all equipment to their original condition and position.
Data:
Part 1: POTATO
Potato
Beginning
length (mm)
After length
(mm)
Change (mm)
Description of
texture/appearance
1
2
3
Conclusion: Use complete sentences.
1) Explain the measurement changes you observed in terms of osmosis.
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
2) Which potato was the experimental control? What was its purpose?
_________________________________________________________________________
_________________________________________________________________________
3) Describe the appearance or texture of the potato soaked in tap water, compared to the control.
How do you explain this?
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
4) Describe the appearance or texture of the potato soaked in beaker B, compared to the control.
How do you explain this?
_________________________________________________________________________
_________________________________________________________________________
_________________________________________________________________________
PART 2: OSMOSIS GUMMY BEARS
Hypotheses:
1. If I place a Gummy Bear in tap water, then the size of the bears will:
( increase,
decrease,
remain the same ). Circle your answer.
2. If I place a Gummy Bear in salt water, then the size of the bear will:
( increase,
decrease,
remain the same ). Circle your answer.
Procedure:
1. Obtain 1 plastic cup, 1 Gummy Bear, and 1 ruler.
2. Label the cup with your name and class. You may name your bear if you want 
3. Fill ¾ of the cup with water.
4. Measure your bear (in mm) from top to bottom (length) and from side to side (width) and from
front to back (height). Record the millimeters in the DATA table below.
5. Let your bear swim in the cup overnight.
6. Place the cup on the back tables away from direct sunlight. Let them sit overnight. We will
measure them tomorrow.
Our Gummy Bear “___________________” (nickname)
DATA:
Volume = Length x Width x Height
example
Before Water
After Water
Length (mm)
Width (mm)
Height (mm)
Volume (mm3)
5 mm
2mm
1 mm
10 mm3