# Ap Biology Lab 1: Osmosis and Diffusion

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AP LAB 1: Diffusion and Osmosis Exercise 1A: Title: Diffusion Objectives: * To understand the mechanism of diffusion and its significance in cells. * To understand how solute size and concentration gradients effect diffusion across a selectively permeable membrane. * To understand how a selectively permeable membrane between two solutions effects diffusion between them. Hypothesis: If I observe that a Benedict's test has came back positive for glucose in the beaker when it came back negative initially, the color of the bag has been tinted from initially being clear, and the mass of the bag has increased; then I will conclude that the dialysis tubing is permeable to glucose, iodine potassium-iodide, and water but not starch, and diffusion has occurred. Procedure: 1. Fill a beaker two-thirds full of water and add approximately 20 drops of IKI. Write down the solution's color and record the mass of the bag. 2. Do an initial Benedict's test on the 15% glucose/1% starch and the beaker solutions for glucose by putting some of the solution and a roughly equal amount of blue Benedict's solution in a test tube, placing the test tube in boiling water for 90 seconds, and observing whether or not the solution changes color from blue. 3. Form a bag out of dialysis tubing by tying off one end, putting in enough 15% glucose/1% starch solution to fill it halfway, and tying off the other end leaving the other half of the bag void of anything (even air). Write down the solution's color. 4. Submerge the bag in the beaker and leave overnight. 5. Dry off the bag and then record its mass. After this write down the color of the bag and the beaker solutions and then test the bag and beaker solutions for the presence of glucose. Picture: Diffusion Lab Setup Picture 1.1 Data: Diffusion Lab Data | Initial Contents | Solution Color | Presence of Glucose