DIFFUSION AND OSMOSIS EXPERIMENT Name: _______________________ PURPOSE: To determine the permeability of the dialysis tubing to different chemicals. THEORY: The cell membrane determines what substances can diffuse into a cell. This characteristic of a cell membrane is called permeability. Many cells are selectively permeable - some substances can pass through the membrane but others cannot. Dialysis tubing is an artificial semi-permeable membrane with similar properties to the cell membrane. MATERIALS: METHOD:

1. Cut 3 strips of dialysis tubing, each approximately 15 cm long. Open the tube by wetting your fingers and gently rubbing each end of the tube. Tightly tie one end of each tube.

2. Pour 10 mL of starch solution into the first dialysis tube. Gently press air out of the open end of the tube in order to make the tube firm. Tightly tie it. Rinse the tube with deionized water.

3. Take the mass of the starch solution filled tube and record it in the data section. Place it in a

marked cup labelled “starch.” Record the appearance of the tube and solution in the data section.

4. Pour 10 mL of iodine solution into the second dialysis tube. Gently press air out of the open end of the tube in order to make the tube firm. Tightly tie it. Rinse the tube with deionized water.

5. Take the mass of the iodine solution filled tube and record it in the data section. Place it in a

marked cup labelled “iodine.” Record the appearance of the tube and solution in the data section.

6. Pour 10 mL of sodium bicarbonate solution into the third dialysis tube. Gently press air out of the open end of the tube in order to make the tube firm. Tightly tie it. Rinse the tube with deionized water.

7. Take the mass of the sodium bicarbonate solution filled tube and record it in the data section.

Place it in a marked cup labelled “sodium bicarbonate.” Record appearance of the tube and solution.

8. Fill the cup labelled “starch” with Iodine Solution. Fill the cup labelled “Iodine with starch

solution. Fill the cup labelled “sodium carbonate” with vinegar.

• Dialysis tubing • Vinegar • Distilled Water • Sucrose solution • measuring cylinders (10 mL) • Starch solution • Cups • Rubber Bands or String • Marking pen • Iodine • Sodium Bicarbonate Solution • Balance

1 2 3

10ml Iodine Solution

Starch Solution

10ml Starch

Iodine Solution

10ml Sodium Bicarbonate

Vinegar

DIFFUSION AND OSMOSIS EXPERIMENT Name: _______________________

9. Allow the cups to sit for 30 minutes.

10. Observe and record the appearance of all the tubes and cups.

11. Carefully remove each tube, rinse them with deionized water, and gently pat them dry. Take their mass and record it in the data table.

DATA: Test Cup One Test Cup Two Test Cup Three Substance in Tube

Substance in Cup

Observations of inside of the tube BEFORE

Observations of inside of the tube AFTER

Observations of Cup BEFORE

Observations of Cup AFTER

Mass of Tube Before

Mass of Tube After

DIFFUSION AND OSMOSIS EXPERIMENT Name: _______________________ Analysis: How to calculate the percentage change in mass: relative change in mass = (mass after – mass before) ÷ mass before

Multiply the relative change in mass by 100% to get percentage change. Test Cup One

1. What was the percentage change in mass? 2. A. Did anything move from the tube to the liquid in the cup?

B. What moved?

C. Describe the evidence that lead you to the conclusion that movement occurred.

3. A. Did anything move from the liquid in the cup to the tube? B. What moved?

C. Describe the evidence that lead you to the conclusion that movement occurred. Test Cup Two

1. What was the percentage change in mass?

2. A. Did anything move from the tube to the liquid in the cup?

B. What moved? C. Describe the evidence that lead you to the conclusion that movement occurred.

4. A. Did anything move from the liquid in the cup to the tube?

B. What moved? C. Describe the evidence that lead you to the conclusion that movement occurred.

DIFFUSION AND OSMOSIS EXPERIMENT Name: _______________________ Test Cup Three

1. What was the percentage change in mass?

2. A. Did anything move from the tube to the liquid in the cup?

B. What moved? C. Describe the evidence that lead you to the conclusion that movement occurred.

5. A. Did anything move from the liquid in the cup to the tube?

B. What moved? C. Describe the evidence that lead you to the conclusion that movement occurred. CONCLUSION: What substances can move through the semipermeable dialysis tubing?

What substances cannot move through the semipermeable dialysis tubing?