Featured in PASCO’s College Biology Instructor Guide

College Biology Instructor Guide


College Instructor edition with 26 experiments covering introductory and general biology topics.


Lab Summary

Use a water quality sensor and colorimeter to measure the conductivity, pH, and absorbance of two solutions separated by a semi-permeable membrane.


Students will investigate the following concepts related to diffusion and membrane permeability:

  • Determining concentration gradients by evaluating movement of molecules across a semipermeable membrane.
  • Determining which molecules are small enough to cross the membrane.
  • Determining the rate of diffusion across the membrane.


Students will gain experience conducting the following procedures:

  • Setting up an experiment to measure rate of diffusion out of a dialysis bag containing pickle juice.
  • Collecting data from three different probes to determine which molecules or ions are diffusing across the dialysis membrane.
  • Using evidence from their experiments to make claims about which molecules or ions are diffusing across the dialysis membrane.

Sensors / Equipment Used:

PASPORT Water Quality Sensor


Measures temperature, conductivity, pH/ISE/ORP and dissolved oxygen. It is specifically designed for convenience in conducting water quality lab experiments. For use with PASPORT Interfaces.

PASPORT Colorimeter Sensor


Our PASPORT Colorimeter records all 4 wavelengths simultaneously--no need to guess at wavelength to get a quality measurement.

Materials Used:

Beaker 100-mL - 2
Beaker 400-mL 
Cuvettes (with colorimeter) - 2
Dialysis tubing - 28 cm
Disposable pipet - 4
Distilled water - 200 mL
Labeling marker 
Lint-free tissue 
Pickle juice - 50 mL
Plastic wrap - 1 per class
Roll of paper towels - 1 per class
Wash bottle filled with water - 1 per class

The Associated Bundle:

College Biology Bundle


A complete probeware bundle designed for PASCO's College Biology curriculum

Interface Required

This experiment may require software and an interface for data collection.