EVERYDAY SCIENCE

Detailed explanation-1: -After two hours, the starch solution in the dialysis tubing turns blue-black. The iodine solution remains the same color (it doesn’t change colors). What do Julian’s results show about the permeability of the tubing? The dialysis tubing is permeable to iodine but not to starch.

Detailed explanation-2: -Starch does not pass through the synthetic selectively permeable membrane because starch molecules are too large to fit through the pores of the dialysis tubing. In contrast, glucose, iodine, and water molecules are small enough to pass through the membrane. Diffusion results from the random motion of molecules.

Detailed explanation-3: -How are you going to determine if iodine and/or starch diffuse across the dialysis tubing?-If both starch and iodine are able to diffuse across the dialysis tubing they would mix on both sides of the membrane turning both solutions dark purple.

Detailed explanation-4: -The dialysis tubing is selectively permeable because substances such as water, glucose, and iodine were able to pass through the tubing but the starch molecule was too large to pass. 3.

Detailed explanation-5: -So what happened? The Dialysis tubing provides a semi-permeable membrane. Only allowing smaller molecules to pass through it. Iodine molecules are small enough to pass freely through the membrane, however starch molecules are complex and too large to pass through the membrane.