Day 3/4  

How is osmosis different from diffusion?  How can Excel be used to visualize the effect of varying concentrations of solutions on osmosis?

Objectives:

Students explain how cells maintain homeostasis through membrane permeability.

Students conduct an experiment that illustrates how cells maintain equilibrium by diffusion and osmosis.

Texas and National Standards

1A, 2A,B,C,D, 3A,C,E,  4B

Materials:

Osmosis Experiment Handout

PowerPoint presentation – “Graphing with Excel”

1 Dialysis tubing (2.5 cm X 30 cm)

1 Beaker or plastic drinking cup

~200 ml distilled water

0.2 M sucrose

0.4 M sucrose

0.6 M sucrose

0.8 M sucrose

1.0 M sucrose1 marking pencil and labeling tape

string for tying dialysis bags

paper towels

calculator

electronic balance

Stella model of osmosis

Activities:

1. Students conduct a quantitative osmosis experiment (hand out). 
2. Teacher directed discussion to explain how to use Excel to analyze data and make predictions regarding trends in the data. ( PowerPoint presentation – "Graphing with Excel")
3. Students record results from experiment.
4. Students create a graph of results using Excel.  See graph rubric.  See lab report rubric.
5. Students manipulate data to analyze a variety of conditions that could occur in the environment of a cell such as additional change in concentration of the solution surrounding the cell.  (Gathering additional data without further experimentation.)