Through the use of demonstrations and interactive discussion, the basic concept of simple diffusion without a selectively permeable membrane is elucidated. Students are then able to take lecture notes with a simple idea of what is being discussed.

THE CELL Cells have particular structures that underlie their functions. Every cell is surrounded by a membrane that separates it from the outside world. Inside the cell is a concentrated mixture of thousands of different molecules which form a variety of specialized structures that carry out such cell functions as energy production, transport of molecules, waste disposal, synthesis of new molecules, and the storage of genetic material.

Observation Inference

Materials needed: 1. Perfume or room spray 2. Three beakers, food coloring, hot plate 3. Two Erlenmeyer flasks, food coloring, index card

concept mapping quiz

1. As students enter the classroom, spray a strong perfume or room spray (use a lot) so that the students at the front of the classroom begin to complain. This leads to a discussion of the movement of molecules and therefore, to a simple definition of diffusion of molecules from high to low concentration. 2. Take a beaker and fill with water, add 2-3 drops of food coloring. Observe what happens and relate this to the previous demonstration. The difference being that this is now working in an aqueous environment not a gaseous one. Once students understand what has happened, take three beakers with cold, warm, and hot water. Ask them if there will be any differences in the beakers now when food coloring is added. They should remember that atoms/molecules move faster when heated so the hot water with food coloring should diffuse faster. 3. This should be set up and let stand for about 15-20 minutes while lecture notes are given. This last demonstration illustrates how more than one molecule can be moving at one time. Take an Erlenmeyer flask (1 liter works best), fill it with water (use warm or hot), and put 5-6 drops of red food coloring in it and mix. Do the same with the second flask except use blue food coloring. Place an index card over the mouth of the first flask and invert it. Put it over the second flask. Gently, remove the index card allowing the two liquids to mix. The students will observe a purple section developing at the interface and spreading throughout the flasks.

Technology Requirements/Integration  (help)

NA

Copyright © 1997-2003 Career Connection to Teaching with Technology USDOE Technology Innovation Challenge Grant Marshall Ransom, Project Manager All rights reserved.