Diffusion across a Selectively Permeable Membrane

In the lab, Diffusion across a Selectively Permeable Membrane,  students investigate the effects of molecule size on diffusion across a synthetic selectively permeable membrane (dialysis tubing) and discuss applications to understanding the selectively permeable cell membrane.This activity includes a demonstration of osmosis (diffusion of water across a selectively permeable membrane).

Download Student Handout: PDF format or Word format

Download Teacher Preparation Notes: PDF format or Word format

We invite comments on this Hands-On Activity and the accompanying Teacher Preparation Notes, including suggestions for other teachers who are planning to use the activity, useful preparatory or follow-up activities, additional resources or any questions you have related to the activity, or a brief description of any problem you might have encountered. If you have a relevant Word document you would like to have posted on this comments page, such as a version of the protocol you have used in your classroom, or if you would prefer to send your comments or questions in a private message, please write Ingrid Waldron at iwaldron@sas.upenn.edu.

See also a complete list of activities:
Hands-on Activities for Teaching Biology to High School and Middle School Students


iwaldron's picture

2011 revision

The Student Handout has been streamlined and the questions have been focused on the topic of diffusion across a selectively permeable membrane.

iwaldron's picture

2009 revision


The major change is the addition to the Teacher Preparation Notes of two ways to modify the activity: (1) to focus on osmosis specifically or (2) to help students develop a more sophisticated understanding of how molecules move across biological membranes.


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