Warm-up: Imagine the following experimental set-up.
If the solute CANNOT move through the semi-permeable
membrane, PREDICT what would happen.
OSMOSIS!!!
Objectives:
Students will describe the phenomenon of osmosis.
Students will demonstrate their understanding of osmosis by deducing the concentrations of
three mystery sucrose solutions.
Students will design, conduct, and evaluate an original experiment to determine the
concentrations of three mystery sucrose solutions.
Your challenge:
Based upon your understanding of the principle of OSMOSIS, can you deduce the
CONCENTRATIONS of THREE MYSTERY SUCROSE SOLUTIONS?
STEP 1: In your Biochem Journal, write your PURPOSE section:
1. QUESTION:
2. Independent Variable:
3. Dependent Variable:
4. HYPOTHESIS: Expressed as three separate statements
“If the mass of the cellulose bag goes up, I conclude that…”
“If the mass of the cellulose bag stays the same, I conclude that…”
“If the mass of the cellulose bag goes down, I conclude that…”
OSMOSIS!!!
Your challenge:
Based upon your understanding of the principle of OSMOSIS, can you deduce the
CONCENTRATIONS of THREE MYSTERY SUCROSE SOLUTIONS?
STEP 2: In your Biochemistry Journal, write your PROCEDURE section:
1. Read and consider the “OSMOSIS – Provided Information” handout.
2. Using the provided materials, design and complete a simple experiment to determine the
concentrations of three Mystery Sucrose Solutions.
3. Write a DETAILED PROCEDURE and DRAW your EXPERIMENTAL SET-UP!!!
TO HELP you with your PROCEDURE: Heres a HINT…
Data Table: Change in Mass (in grams) of cellulose bags containing indicated Mystery Sucrose Solutions
Contents of Cellulose Bag
Mystery Sucrose Solution A
Mystery Sucrose Solution B
Mystery Sucrose Solution C
Initial Mass (grams)
Final Mass (grams) Change in Mass (grams)
OSMOSIS - Provided Information
Provided Materials:
Reference Sucrose Solution
Mystery Sucrose Solution A
Mystery Sucrose Solution B
Mystery Sucrose Solution C
Cellulose dialysis tubing
Beakers of various sizes
1 mL plastic pipettes
Masking Tape
Sharpies
Timer
Digital Scale
Paper towels
Provided information:
Sucrose
commonly called table sugar, is a disaccharide of glucose and fructose
molecular formula C12H22O11
1. Sucrose CANNOT diffuse through a cellulose membrane.
2. The Reference Sucrose Solution has a concentration of 0.5 M sucrose.
3. One Mystery Sucrose Solution has a concentration of 0.0 M sucrose
(that is, there is NO sucrose in the solution)
4. One Mystery Sucrose Solution has a concentration of 0.5 M sucrose
5. One Mystery Sucrose Solution has a concentration of 1.0 M sucrose.
OSMOSIS!!!
Your challenge:
Based upon your understanding of the principle of OSMOSIS, can you deduce the
CONCENTRATIONS of THREE MYSTERY SUCROSE SOLUTIONS?
STEP 3: Conduct your PROCEDURE and collect your DATA!!!
Data Table: Change in Mass (in grams) of cellulose bags containing indicated Mystery Sucrose Solutions
Contents of Cellulose Bag
Mystery Sucrose Solution A
Mystery Sucrose Solution B
Mystery Sucrose Solution C
Initial Mass (grams)
Final Mass (grams) Change in Mass (grams)
OSMOSIS!!!
Your challenge:
Based upon your understanding of the principle of OSMOSIS, can you deduce the
CONCENTRATIONS of THREE MYSTERY SUCROSE SOLUTIONS?
STEP 3: Write your CONCLUSIONS by answering the following questions in your Journal.
COUNTS AS A 9 POINT LAB CLASSWORK
1. a) What is the concentration of Mystery Sucrose Solution A? __________M
b) How can you tell? Please explain using the terms hypertonic, hypotonic, or isotonic.
2. a) What is the concentration of Mystery Sucrose Solution B? __________M
b) How can you tell? Please explain using the terms hypertonic, hypotonic, or isotonic.
3. a) What is the concentration of Mystery Sucrose Solution C? __________M
b) How can you tell? Please explain using the terms hypertonic, hypotonic, or isotonic.
THINGS I’LL NEED
Mystery Solution A – 50 to 100 mL in an Erlenmeyer with a 1 ml dropper pipet
Mystery Solution B - 50 to 100 mL in an Erlenmeyer with a 1 ml dropper pipet
Mystery Solution C - 50 to 100 mL in an Erlenmeyer with a 1 ml dropper pipet
Reference solution = 0.5 M sucrose (several liters) in large Erlenmeyers or bottles
Minimum 32 beakers
20 cm cellulose tubing strips minimum 30 per class
Masking tape and sharpies