Excel Diffusion Models Read Me
Excel Color Diffusion Model
To use the color diffusion model
1. In the appropriate grid square, record the number of drops of food coloring that are dropped into the water pan. Hit the return key. This represents the first time step of the model.
2. Hit the F9 key for each additional time step.
3. Students should try to find an appropriate amount of time each time step represents compared to the data they collected from their experiment.
4. The cells are reset to 0 by clicking the Reset Values button.
Excel Odor Detection Model - The odor detection model can be used in two ways.
To graphically illustrate the odor data collected by the class:
1. Enter a 1 in the appropriate grid for each student as she detects the vanilla. Hit the Return key.
2. Students can be added as they smell the vanilla. The grid will be recalculated after each cell has a value added.
To predict the data collected by the class:
1. Enter a 1 where the odor is placed. Hit the return key. Hit the F9 key for each additional time step. Note: the darker color is present where the cell value is .71 or greater.
The cells are reset to 0 by clicking the Reset Values button.
Notes for both models.
· The color model does not account for conservation of mass, i.e., the iterations can be continued until the entire grid is the color of the original drops of color.
· Both models can be changed to manual calculations by selecting Options from the Tools menu. Select the Calculations tab and select the Manual button. Values can be entered into appropriate cells and then calculations will be performed only when the F9 key is hit.
· Excel calculates the values for cells in a specific order. Some cells are calculated before other cells. This causes cells which should have the same values to have slightly different values. For example, if you enter a 1 into cell E5 on the 9x9 Odor Template and hit return, mirrored cells should have the same values. This is true for D5 and F5, but E4 and E6 are not the same values. A greater difference is seen for E4 and F6. The mirrored cells with the lower values are calculated before the higher values, i.e., there are more cells with numbers when the higher valued cells are calculated. This difference dissipates as more iterations are performed or more values are added.