Osmosis and DiffusionDemosName:

BiologyDate: Period:

A. Osmosis –Vegetable Demo

  1. Compare the vegetables in the three trays with regard to flexibility and pliability.

Tray A
Tap Water / Tray B
Salt Water / Tray C
Freshly Cut
  1. List the trays in order from least flexible or pliable (bendable) to most pliable (bendable).
  1. The cells of the vegetables in Tray ______appear to have lost water.
  1. The cells of the vegetables in Tray ______appear to have gained water.
  1. Draw a picture of a cell that has been placed in a hypotonic solution. What happens to cells placed in this type of solution?
  1. Draw a picture of a cell that has been placed in a hypertonic solution. What happens to cells placed in this type of solution?
  1. Draw a picture of a cell that has been placed in an isotonic solution. What happens to cells placed in this type of solution?
  1. Identify the three trays using the following terms: isotonic, hypotonic, and hypertonic.

Tray A ______solution

Tray B ______solution

Tray C ______solution

B. Diffusion Demo

Introduction: In this demo 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. Watch as your teacher demonstrates how iodine changes in the presence of starch.Describe what happened when iodine came into contact with starch.

Procedure for the Demonstration:

  1. Fill a plastic baggie with a teaspoon of corn starch and a half a cup of water tie bag.
  2. Fill a beaker halfway with water and add ten drops of iodine.
  3. Place the baggie in the cup so that the cornstarch mixture is submerged in the iodine water mixture.
  4. Wait fifteen minutes and record your observations in the data table.

Questions:

  1. What is the main difference between osmosis and diffusion
  1. Molecules tend to move from areas of ______concentration to areas of ______concentration.

Make Some Predictions

  1. If the baggie was permeable to starch, which way would the starch move, into or out of the bag? (circle one)
  1. If the baggie was permeable to iodine, which way would the iodine move, into or out of the bag? (circle one)
  1. If the baggie was permeable to iodine, what color would you expect the solution in the baggie to turn? What about the solution in the beaker?
  1. If the baggie was permeable to starch, what color would you expect the solution in the baggie to turn? What about the solution in the beaker?

Data Table

Starting Color / Color after 15 minutes
Solution in Beaker
Solution in Bag

Post Lab Analysis

  1. Which substance moved, the iodine or the starch? How did you determine this?
  1. The plastic baggie was permeable to which substance?
  1. Is the plastic baggie selectively permeable? How do you know?
  1. Sketch the cup and baggie in the space to the right.

Use arrows to illustrate how diffusion occurred in this lab.

  1. What would happen if you did an experiment in which the iodine solution was placed in the baggie, and the starch solution was in the beaker? Be detailed in your description.