Advanced PlacementCollegeHigh School / Biology


Students use a pH sensor to investigate the diffusion of hydrogen ions through a semipermeable membrane, comparing the rates of diffusion for two solutions that differ in their acidity.

Dialysis tubing sacs are filled with solutions that have different initial pH values. The sacs are placed in water and a pH probe is used to measure the change in water pH over time. Students determine if and how the difference in rate of pH change relates to the difference in initial pH of the solution in each sac. Students then consider variables other than initial pH that might affect the rate of H+ ion diffusion and design an experiment that tests the effect of that variable on the diffusion rate of a cell, using the beaker-tubing system to model the cell.


Student Files

2_ABI_Diffusion.cap 7.82 KB
2_ABI_Diffusion_S.docx 233.63 KB
2_ABI_Diffusion_S.pdf 353.10 KB
2_ABI_Diffusion.spklab 7.20 KB

Teacher Files

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Standards Correlations

IB Topics AP Topics
1.4; 10.3 2-1.C; 2-2.C; 2-2.F; 2-2.I

Featured Equipment

pH Sensor

Wireless pH Sensor

Here’s the best tool for measuring pH since litmus paper. The Wireless pH Sensor connects via Bluetooth® to monitor the pH of solutions.

Many lab activities can be conducted with our Wireless, PASPORT, or even ScienceWorkshop sensors and equipment. For assistance with substituting compatible instruments, contact PASCO Technical Support. We're here to help.

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Source: Lab #02

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