Diffusion Activity Procedure 1. Obtain 2-3 inches of dialysis tubing. 2. Rinse the tubing with water until it is soft. 3. Rub one end of the tubing between your finger and thumb to open. 4. Tie the end of the tubing in a knot with a piece of string or elastic. 5. Add enough of the starch-sugar solution (prepared by the teacher) to fill to approx. 1 inch from the top. Use a funnel to pour the starch-sugar solution in. 6. Tie the top of the starch solution with another piece of string. 7. Rinse the entire tubing and string underneath running water. 8. Obtain a beaker. Fill the beaker half full of water. 9. Obtain the iodine. Add enough iodine to turn the water to a dark yellow/orange colour. Observations Before After Key Questions 1. Why did the reaction take place in the dialysis tubing and not in the surrounding solution? 2. How does this activity relate to a cell membrane? 3. A cell membrane is referred to as being selectively permeable. What does this mean? 4. What is diffusion? 5. What is a concentration gradient? 6. What materials diffusion across a cell membrane?
