Diffusion Is a General Phenomenon in the Environment

Introduction/ Purpose of Experiment: Diffusion is a general phenomenon in the environment. The speed of diffusion is dependent on such factors as the temperature, the size of the molecule, and the type of medium. The purpose of this experiment is to define and describe the purpose of diffusion. During the tests we shall predict which substances will or will not diffuse across a plasma membrane.

Procedure or Methods Section:

EXPERIMENT 1 "Through a Liquid"

During the first experiment, through a liquid, we filled the bottom of a glass petri dish with water. Next we positioned the dish onto a flat ruler and added one crystal of potassium permanganate (KMnO4) directly over the millimeter measurement line. We set a timer for ten minutes, and when the timer went off the group recorded the distance it moved, the final time, and length of time.

EXPERIMENT 2 "Through Air"

During the second experiment, through air, three of the four people in the group stood exactly one foot away from each other, while the fourth waited seconds to begin the process of the experiment. The fourth person sprayed the substance into the air, while the other three waited until they smelt the fragrance in the air. The last step was to record the data.

EXPERIMENT 3 "Diffusion across Plasma Membrane"

During the third experiment, diffusion across plasma membrane, we took a piece of dialysis tubing and soaked it into water until it was pliable. Next we halfway filled the bag with glucose solution and added four drops of starch solution to the bag. We tightly held the open end of the bag together as we shook the bag, mixing the solutions, and then we rinsed the bag with purified water. Afterwards, we put 2/3 of water into a beaker and added drops of iodine solution until a light yellow color appeared. We placed the bag in the beaker with the open end hanging over the edge. After five minutes the group recorded data: color change, and color change in bag contents.

Presentation of Data:

EXPERIMENT 1-2 "Through a Liquid" & "Through Air"

Medium Time Zero Final Time Length of Time (hr) Distance Moved(mm) Speed of Diffusion (mm/hr)

Semisolid ---------------- ---------------- ---------------- ---------------- ----------------