Investigation: Modeling Diffusion


This inquiry investigation requires students to cut agar into 3 shapes (small, medium, large) and compare the rates of diffusion of a substance (vinegar) into the cell.   The agar is infused with bromothymol blue, which will turn to yellow when it becomes acidic from the vinegar.  

Students collect data on the volume of the cubes, the surface area, and the rates of diffusion.

Finally, students are given the task to create a large cell with the fastest rate of diffusion.  Their cell will be compared to other designs.   Students will learn that cells are small because of the surface area and volume ratio.  Large cells cannot move required nutrients across their membranes fast enough to support their needs.

Worksheet includes instructions for creating agar molds.

Grade Level:  9-12  |  Time Required:  45 min – 1 hr

HS-LS1-2 Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms