Osmosis – Sandwich Bags

Activity Summary
The activity will show how molecules move in a predictable manner and how these patterns drive physiological functions such as those within the lungs. Students will seal starch in a sandwich bag and place it in a beaker with a few drops of iodine. The iodine will diffuse into the bag and stain the starch. The students will then place potato cores in varying concentrations of
sucrose solution. The swelling of the cores shows the process of osmosis.

Grade Levels
9-12

Learning Objectives
1. Define osmosis and diffusion
2. Distinguish between hypertonic and hypotonic solutions
3. Predict which direction water will move across a semipermeable membrane, given the concentrations on either side
4. Give examples of diffusion and osmosis in nature

Lesson Materials (view or download)
PowerPoint
Lesson Plans

Keywords
osmosis, diffusion, solute, solvent, tonicity

Last updated: 3/3/2015