Strand 7:3 Structure and function of life.
Standard 7.3.2 Develop and use a model to describe the function of a cell in living systems.
Title: 3D Measuring Osmosis
Description: Students will design an experiment to measure osmosis using a dialysis membrane and different solutions.
Time needed: 2 fifty minute periods.
Materials: Have available for students: dialysis membrane cut into 5 or 6 inch strips and soaked. Concentrated solutions of starch, iodine, sugar, and salt water. Dental floss or rubber bands to tie off the bags. Large beakers (500-1000 mL) balances, graduated cylinders, food coloring
Description:
1. Begin with a “phenomenon”. Suggested videos: https://www.youtube.com/watch?v=FyYz-1gqt68
This would be a fun phenomenon to do with the students. You would have to plan ahead and create your “shell-less” eggs ahead of time. Students would enjoy seeing the process of removing the shell also.
2. Read the challenge to the students and show them what materials they have to work with.
3. Ask students to make a plan to test some combination of the solutions. If time allows they could create a “bag” to begin with the next day or even to start the experiment by placing it in another solution.
4. On the second day, student groups should all be able to run at least one experiment. Remind them to collect qualitative and quantitative data.
5. Ask student groups to be ready to report their findings.
Student Sheet Name______
Period______
Title: Measuring Osmosis
Phenomenon. Water particles can move through a semi-permeable dialysis tubing or cell membrane (like the egg membrane). In this activity you will design an experiment, predict and measure the direction of the particle movement. You will create a drawing to model your explanation.
Problem: How can I measure osmosis and create a model to explain it?
Procedure (What will you do to measure the movement of water through the membrane?)
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Hypothosis: Write an if/then statement predicting the direction of osmosis and the predicted amount of increase. ______
Materials:
1.
2.
3.
4.
5.
6.
7.
Observations:
Analysis:
1. Sketch your experiment(s) and the direction of particle motion.
2. How is your model like a cell?
3. How is your model different from a cell?
Conclusion:
My model demonstrates osmosis because ______