Introduction: In this lab you will observe the diffusion of a substance across a semi permeable membrane. Iodine is a known indicator for starch. An indicator is a substance that chances color in the presence of the substance it indicates.
Prelab Observations: Describe what happened when iodine came into contact with starch. Drop a very small amount of iodine on a piece of paper and observe what happens to the paper. (Paper has lots of starch in it)
The Iodine turned black on the paper.
-plastic baggie/cheap works well
-water (tap is fine—or bottled)
-iodine (use caution if you are allergic to iodine/betadine)
-about a 2 cup size cup/beaker/bowl—clear would be great
Fill a plastic baggie with a teaspoon of corn starch and a half a cup of water tie bag.
Fill a cup (about a two-cup size)halfway with water and add ten drops of iodine.
Place the baggie in the cup so that the cornstarch mixture is submerged in the iodine water mixture.
Wait fifteen minutes and record your observations in the data table (picture after 15 minutes)
1. Define diffusion. The spreading of something more widely, the action of spreading the light from a light source evenly so as to reduce glare and harsh shadows.
2. Define osmosis. Diffusion of fluid through a semipermeable membrane from a solution with a low solute concentration to a solution with a higher solute concentration until there is an equal concentration of fluid on both sides of the membrane.
3. What is the main difference between osmosis and diffusion. Osmosis transports through the membrane of an object while diffusion spreads across an object.
4. Why is iodine called an indicator? It indicates color when in contact with starch.
5.Molecules tend to move from areas of High concentration to areas of Low concentration.
What is in the Bag?
Were going to think about concentrations now, which substances are more or...