The Process of Diffusion

Research Questions:

• What is the difference between osmosis and diffusion?
• How is diffusion regulated?

You can see beautiful colors everywhere you look! There is a lot of science behind the colors that you see. Color is the property that our eyes visually perceive and is derived from the spectrum of light. White light is a blend of all the spectrum colors which include red, orange, yellow, green, blue, indigo, and violet. Individual colors of white light can be seen by using a prism which separates the colors and, in turn, white light can be seen when the spectrum colors are combined in such a fashion as a spectrum spinner.

Materials:

• 1 plastic baggie
• Corn starch
• Iodine
• Tap water
• Stopwatch
• Twist tie or rubber band
• Clear drinking glass

Experimental Procedure

1. Place ½ cup of water and 1 tsp of corn starch into the baggie.
2. Seal the baggie and also place the twist tie or rubber band on it as an extra security measure.
3. Fill your drinking glass half full with tap water.
4. Place 8 - 12 drops of iodine in the water.
5. Place the baggie with the corn starch solution in the glass with the iodine solution. Make sure the corn starch solution is submerged in the iodine solution.
6. Wait 15-20 minutes.
7. Remove the baggie from the glass and place it on a paper towel. Do not unseal the baggie.
8. What do you notice about the color of the two solutions?
9. Complete Table 1.
10. Which solution passed through the baggie? Which solution did not pass through the baggie?
11. Explain why one solution could and one could not pass through the baggie.
12. Hypothesize what the results would be if the two solutions were to switch their placement (iodine solution in the baggie and corn starch solution in the glass). If time permits feel free to test your hypothesis.

Terms/Concepts: Solution concentration; Cell membrane; Selective permeability; Diffusion; Osmosis

References:

http://www.biologycorner.com/bio1/diffusion.html

http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/diffus.html

http://science-class.net/PowerPoints/Diffusion_osmosis.ppt