Abstract This experiment was designed to identify basic structures of cells, understand semi-permeability and that the cell membrane holds this characteristic, and to study the effects that concentration gradients have on the rate of diffusion. The purpose of this experiment was to learn if the concentration affected the rate of diffusion, and if another solute could change the rate of diffusion. For the procedure we used microscopes and an Elodea leaf to study the diffusion of water and a sugar solution, and dialysis tubing, a beaker filled with water, and a conductivity probe to determine the rate of diffusion of the semi-permeable dialysis tube filled with different solutions. We found that the more concentrated a solution was, the faster the rate of diffusion was. In the Elodea Leaf, we found that the higher concentrated solution made the cell membrane separate from the cell wall, because the water was leaving the cell and moving to the more concentrated are. We also found that the higher concentrations had a faster rate of diffusion because the water molecules were more attracted to the salts in the solution, and the salts in the solution wanted to move from the dialysis tube (more concentrated) into the beaker where it was less concentrated. Introduction Diffusion occurs spontaneously, and is when a substance moves from a region of high concentration to a region of less concentration. (Reece et al., 132). Diffusion is the process that describes small molecules moving across the cell membrane (132). Since cell membranes are semipermeable, some molecules can move freely through it (133). Hydrophobic molecules (polar-covalent bonds) can move through cell membranes, but hydrophilic molecules (non-polar covalent bonds) cannot (131). Ions cannot freely move through the cell membrane, so they must be transported by transport proteins (131). Some transport proteins create passageways called ion channels, which act as gated channels that