Setup the model by pressing either the SETUP-RANDOM or the SETUP-SIDE buttons at the top of the Interface tab. SETUP-RANDOM distributes all the molecules randomly around the screen. SETUP-SIDE distributes the blue molecules evenly, while placing the red molecules on the right side of the screen.

1. Press GO to watch the molecules move about the screen as they achieve equilibrium.

2. The plot tracks the relative concentrations of each color molecule on each side of the central divider.

a. If the red line dips below 0, there are more red molecules on the left side of the divider than on the right.

b. If it rises above 0, there are more red molecules on the right side of the divider than on the left.

c. The blue line plots the same relationship for blue molecules.

You can add more red molecules to the right side of the screen by pressing ADD RED.

*THINGS TO NOTICE

Pay attention to the plot and compare it to what you see in the graphics screen. Is there an equal number of blue and red molecules on each side of the divider according to the plot and according to what you perceive in the graphics screen?

Activities

Click the Random Setup button.

1. What is the concentration of red anions on the Left and Right side of the model before it starts? Write the numbers below.

Left Side Right Side

2. What was the concentration of red anions on the left and right side of the model at time 400? Write the numbers below.

Left Side Right Side

3. What did it mean when the red and blue lines crossed and then ran along together as the plot proceeded?

4. How would you describe the solution on the left side of the model after a time of 400?

Isotonic, Hypotonic or Hypertonic

5. How would you describe the solution on the right side of the model after a time of 400?

Isotonic, Hypotonic or Hypertonic

Click on the Setup Side button.

6. What is the concentration of red anions on the Left and Right side of the model before it starts? Write the numbers below.

Left Side Right Side

Click the Go button. Count 1 and 2, and Click the Go button a second time. This will stop the motion of the molecules and the plot. Now answer the questions below:

7. The red and blue lines are above the middle of the zero line on the plot. What does their position, and separation, on the graph indicate about the concentration of the solute and solvent on the right side of the model? Explain.

8. How would you describe the solution on the left side of the model?

Isotonic, Hypotonic or Hypertonic

9. How would you describe the solution on the right side of the model?

Isotonic, Hypotonic or Hypertonic

Write a hypothesis to predict what will happen osmotically in the model? Use the following categories in writing your hypothesis of the osmotic situation.

10. Is there a concentration gradient present before the model runs?

Yes No

On which side is the high concentration of water?

11. In which direction will the solute (red anions) move as the model runs?

Left Right

12. In which direction will the solvent (blue-water) move as the model runs?

Left Right

13. What will be the concentration of the water and solute (red) on the left side after the model has run to a time of 400?

More water than solute on the left

Equal amounts of both sides

More solute than water on the left

14. Hypothesis:

Now Click Go and run the model run to a time of 400:

15. Was your hypothesis correct?

Yes No

16. Briefly explain what you have learned about osmosis by using the Kinetics 3 Simulator?