Diffusion and Osmosis Lab (IB)
Name_____________________________________
OBJECTIVES OF THE LAB:
Period _____ Updated Jan.2015 with help on cell model variables



The movement of molecules
* Concentration of a Substance
Diffusion
* Osmosis
How a Cell membrane helps the cell carry out the 4 out of the 10 Characteristics of Life
EXPERIMENT #1- DIFFUSION OF Air Freshener Molecules around the Room
Independent Variable-
Dependent Variable-
Write an Inquiry Question based on the variables you witnessed in this demonstration. Highlight
Definition of Diffusion-
Hypothesis for Diffusion of a Air Freshener: Base this on the variables & the Inquiry Question in
the experiment. Hint: Use the explanation of diffusion for the because part of the Hypothesis.
Created by: Cyndi Colston @ Century Middle School, Thornton Colorado. Ask for Permission to re-print.
EXPERIMENT #2- DIFFUSION OF SUGAR CUBES IN DIFFERENT TEMPERATUREs OF WATER
Materials:
Variables: List ALL Independent, Dependent, & Control Variables present & label them
accordingly.
Write an Inquiry Question based on the variables you manipulated (IV) and the thing you
measured (DV) in this experiment. Highlight the variables!
Hypothesis: for Diffusion of Sugar Cubes in different temperatures of water: Highlight the variables!
Created by: Cyndi Colston @ Century Middle School, Thornton Colorado. Ask for Permission to re-print.
EXPERIMENT #3 (Part A In lab)- Model CELL MEMBRANE
Permeable-
Examples:
Impermeable-
Examples:
Selectively Permeable-
Examples:
Materials:
Created by: Cyndi Colston @ Century Middle School, Thornton Colorado. Ask for Permission to re-print.
Variables: List ALL Control, Independent, & Dependent variables present. *Take out underlined words
Control- same cornstarch mixture in both containers
Independent- different containers that hold the cornstarch
Dependent- the container that is more permeable (allows iodine to pass through the
easiest)
Inquiry Question: Highlight the variables from above!
Hypothesis: for Model: CELL MEMBRANE Highlight the variables from above!
Definition of Osmosis-
WHY IS OSMOSIS HELPFUL TO THE CELL? Use your good biology brain!
Created by: Cyndi Colston @ Century Middle School, Thornton Colorado. Ask for Permission to re-print.
Name 3 analogies for the cell membrane:
1.)
2.)
3.)
Name the Characteristics of Life that are represented by the osmosis/diffusion process a cell under goes.
Name the movement of materials either in or out of the cell…or both.
Characteristic of Life
Movement
1.)_________________________________________________________
________________________________________________
2.) ________________________________________________________
_________________________________________________
3.) _______________________________________________________
_________________________________________________
4.) _______________________________________________________
________________________________________________
CELL MEMBRANES AND PERMEABILTY: ANALYSIS
DATA TABLE:
OBSERVATIONS
DATE _________
SOULTION
__________
__________
__________
Color
Color
COLOR
COLOR
Before
after 10
AFTER
LAST DAY
Putting
minutes of
Experiment
putting
Together
experiment
24 Hours
together
MODEL CELL
(STARCH IN BAGGIE)
STARCH in
The TEST TUBE
IODINE in
BEAKER
Created by: Cyndi Colston @ Century Middle School, Thornton Colorado. Ask for Permission to re-print.
Answer the following questions using complete sentences and Scientific Reasoning
1.) What part of the cell does the plastic bag represent?
2.) What was the Purpose of Placing a test tube containing a starch solution in
the beaker of iodine?
3.) DID THE STARCH MOVE OUT OF THE BAG? YES OR NO AND GIVE evidence for your
answer.
4.) Did iodine move into the bag? Yes or no and give evidence for your answer.
5.) WHEN THE STARCH MIXES WITH IODINE, THE MIXTURE TURNS (color) _____________.
6.) What can you infer about the contents of the plastic BAG? (What’s inside)
Created by: Cyndi Colston @ Century Middle School, Thornton Colorado. Ask for Permission to re-print.
7.) BASED ON YOUR RESULTS, was the model cell Membrane permeable or impermeable to
iodine? ________________________________
WHY is this so? (From previous question)
8.) BASED ON YOUR RESULTS, was the model cell Membrane permeable or impermeable to
STARCH? _________________________________
WHY?
CELL MEMBRANES AND PERMEABILTY: CRITICAL THINKING
9.) CELL MEMBRANES CONTAIN SMALL HOLES, or pores. Pore size may determine why some chemicals
can or cannot pass through a cell membrane. In your model, how might the size of the
membrane pores in the plastic bag compare to the size of the iodine molecules? DRAW THE
molecules and the pore size on the DIAGRAM and show if they moved or not with an .
KEY: MEMBRANE PORES=
IODINE MOLECULES=
Created by: Cyndi Colston @ Century Middle School, Thornton Colorado. Ask for Permission to re-print.
10.) IN THE PREVIOUS PICTURE, SO how Does the size of the membrane pores compare to the size of
the iodine molecules?
WHAT IS THE RESULT of these variables?
11.) NEW IDEA: IN your model, how might the size of the membrane pores compare
to the size of the starch molecules? DRAW THE molecules & pore size on the
DIAGRAM and show if they moved or not with an.
KEY:
MEMBRANE PORES -
STARCH molecules =
Created by: Cyndi Colston @ Century Middle School, Thornton Colorado. Ask for Permission to re-print.
12.) IN THE PREVIOUS PICTURE, SO how does the size of the membrane pores
compare to the size of the starch molecules?
WHAT IS THE Result?
13.) Based on the What you learned from studying diffusion through a
Selectively permeable membrane, what might be the reasons that sick
people wear face masks? BE SPECIFIC
Created by: Cyndi Colston @ Century Middle School, Thornton Colorado. Ask for Permission to re-print.
Created by: Cyndi Colston @ Century Middle School, Thornton Colorado. Ask for Permission to re-print.