TEACHER PRE-LAB GUIDE
FOR DEMONSTRATION:
Materials:
Plastic cups
Gummy Bears
Package of Red Kool-Aid
30% Salt Solution
Celery Stalks
Hot/Cold Water
PREPARATION:
Soak Gummy Bears (one color per cup) overnight in water
Add 150 grams of salt to 500ml of HOT water; mix to dissolve as much as possible
Soak celery stalks in salt water overnight
Soak another celery stalk in tap water overnight
PROCEDURE:
1. As students enter the class, have them look at the demonstrations in the front of the
room.
a. Show students dry Gummy Bears and a cup of water. Ask students to write their
prediction of what will happen if the Gummy Bears are soaked overnight in the water.
b. Show students a cup of salt water and a stalk of celery. Ask students to write their
prediction of what will happen if the celery soaks overnight in salt water.
c. Show students a package of Kool Aid and a cup of hot water and a cup of cold water.
Ask students to write their prediction of what will happen to the Kool Aid when added to
the cup of hot water; cup of cold water.
2. Teacher will now show :
a. Gummy Bears soaked in water
b. Celery in salt water; celery in tap water
c. the effect of adding one teaspoon of Kool Aid into hot water; one teaspoon of Kool
Aid into cold water.
3. Teacher will lead a class discussion of student predictions and explanations of what
they learned.
For Part A: Diffusion:
Materials:
Each group needs:
Gloves —1 pair for each student
1 Plastic bag with 1 teaspoon of corn starch
1 Plastic cup
1 bottle of Lugol’s Solution (iodine)
1 graduated cylinder
Water (150 ml/per group)
Preparation:
1. Measure 1 teaspoon of corn starch and add to a plastic bag; close bag and label bag
Group1, 2, etc.
2. Put a plastic cup, a graduated cylinder, bottle of Lugol’s solution and the plastic bag
with corn starch at each lab group’s station.
3. Provide a large container of tap water at a central location in the classroom
4. Have a place assigned for each group to leave their plastic bag overnight
Procedure:
1. Pass out Part A Introduction and Instructions
2. Ask students to read all of the introduction and lab instructions prior to beginning the
lab
3. Pass out Handout 1, Part A
4. On second day, pass out Handout 2, Part A
For Part B: Osmosis
Materials:
ALL groups need:
1 plastic cup
one 8 inch pre-cut and soaked dialysis tubing
1 graduated cylinder
four 8 inch pre-cut pieces of dental floss
Scales
Gloves – 1 pair per student
Water
Additional Materials Needed:
Groups 1 and 2 need:
20% sucrose solution
Bottle of red food coloring
Groups 3 and 4 need:
Bottle of Phenolphthalein
Household Ammonia
Groups 5 and 6 need:
Bottle of vinegar
Bottle of Universal Indicator Solution
Groups 7 and 8 need:
Distilled water
40 % sucrose solution
Bottle of red food coloring
Preparation:
1. Cut dialysis tubing into 8 inch sections. Each group will need 1 piece.
2. One or two days before the lab, soak the dialysis tubing in distilled water, tubing
should be covered with water.
3. Cut four 8 inch pieces of dental floss for each group: for 8 groups, 32 pieces are
needed.
4. To prepare 20% sucrose solution:
Place 20 grams of sugar in 100ml of distilled water.
To prepare 40% sucrose solution place 40 grams of sugar place in 100ml of distilled
water (if this does not dissolve readily, heat the water to hasten the process).
5. Prior to beginning lab, place the following at each lab station:
1 piece of dialysis tubing in distilled water; 1 plastic cup; 1 graduated cylinder; Four 8
inch pieces of dental floss; 1 pair of gloves for each student
6. At a central location, place scales and tap water.
7. At another central location, have the additional materials needed for each group.
8. Have each group label their plastic cup with their group number.
9. Have a designated place for each group to leave their dialysis tubing in plastic cup
overnight.
Procedure:
1. Pass out Part B Introduction and Instruction
2. Make sure each group member reads all the background information and
instructions before starting.
3. Pass out Handout 1, Part B
4. When Handout 1, Part B is completed and turned in, pass out Handout 2, Part B.
EXPECTED RESULTS:
Part A: the solution inside the bag will eventually become blue – black; the solution
outside the bag will become colorless.
Part B: for Groups 1 &2 the mass of the dialysis tubing will increase and the solution
inside will become pinkish – red; for Groups 3 & 4 the mass of the dialysis tubing will
increase and the solution inside will become pinkish - purple; for Groups 5 & 6 the mass
of the dialysis tubing will increase and the solution will become pinkish – orange; for
Groups 7 & 8 the mass of the dialysis tubing will decrease and the solution in the cup
will become light pink.
ANSWERS HANDOUT 1 PART A:
DATA ANALYSIS QUESTIONS
1. Based on your observations, which substance moved, the Lugol’s solution (iodine) or
the starch? Lugol’s Solution or Iodine
2. How did you determine this? Lugol’s Solution/Iodine is an indicator which turns
starch blue/black over a period of time. The solution in the plastic bag, which
contains the starch, changed to this color and the solution in the plastic cup
became lighter.
3. The plastic bag was permeable (lets particles through) to which substance? It was
permeable to the Lugol’s Solution/Iodine
4. Is the plastic bag selectively permeable (lets some particles through but not all)?
Yes, it did not allow the corn starch to move.
5. Sketch the plastic cup and bag in the space below. Use arrows to indicate the
direction of diffusion in this lab. Answers will vary.
ANSWERS TO HANDOUT 2, PART A
DIFFUSION LAB CONCLUSION/PREDICTION QUESTIONS
1. In your own words define diffusion and give an example. Answers will vary.
2. What happened to the color in the bag that was left overnight? What happened to
the color in the plastic cup that was left overnight? It became darker until it spread
throughout the bag. The color in the plastic cup became lighter.
3. If the water containing Lugol’s solution (iodine) was heated, predict how this would
affect the time of a color change? The rate of the color change in the bag and the
plastic cup would increase.
4. Why is Lugol’s solution (iodine) called an indicator? The Lugol’s solution (iodine)
changes color from brown to black in the presence of the starch.
5. Molecules tend to move from an area of greater (higher) concentration to areas of
lesser (lower) concentration.
6. Is the bag or the plastic cup more concentrated in starch? Bag
7. Is the bag or plastic cup more concentrated in iodine? Plastic Cup
DIFFUSION LAB ELABORATE QUESTIONS
1. Predict which way the starch would move, into the bag or out of the bag, if the bag
was permeable to starch. It would move out of the bag Explain your answer.
Answers will vary.
2. Predict the way Lugol’s solution (iodine) would move, into or out of the bag, since the
bag is permeable to Lugol’s solution (iodine). It would move into the bag.
3. Since the bag is permeable to Lugol’s solution (iodine), what color would you expect
the solution in the bag to turn? Blue/black. Explain your answer. Answers will vary.
What about the solution in the plastic cup? The solution in the plastic cup will get
lighter. Explain your answer. Answers will vary.
4. If the bag was permeable to starch, what color would you expect the solution in the
bag to turn? It would become a lighter blue. Explain your answer. Answers will
vary.
What about the solution in the plastic cup? It would begin to turn blue. Explain your
answer. Answers will vary.
5. Predict what you think would happen if you did an experiment in which the Lugol’s
solution (iodine) was placed in the bag and the starch was in the plastic cup? Answers
will vary. BE DETAILED IN WRITING YOUR PREDICTION
ANSWERS TO HANDOUT 1, PART B
1. Sketch the tubes in the plastic cups and use arrows to show the movement of the
particles for each group. Answers will vary.
Sketch the tubes in the plastic cups and use arrows to show the movement of the water
molecules for each group. Answers will vary.
2. Which of these solutions are hypertonic for each group? Groups 7 & 8. Which of
these solutions are hypotonic for each group? Groups 1, 2, 3, 4, 5 & 6.
3. How do you know which way the particles move? The indicator changed colors in
Groups 3, 4, 5, 6. How do you know which way the water molecules moved? Change
in mass; in Groups 1, 2, 7, 8 by the movement of the red food coloring.
4. How is this similar to particle movement in cells? Answers will vary. How is this
similar to water movement in cells? Answers will vary.
Prepared by: Dr. Debbie Payne, Ruth H. Liddell, Shirley K. Scarbrough
Alabama State University, Math, Science Partnership, Fall 2012