Osmosis Lab

Mrs. Pfahnl’s Bio A Lab: Osmosis

Osmosis is a passive transportation of water molecules through semipermeable cell membrane.

The purpose of the experiment is to investigate the different salt levels affects the intake or output of the water molecules of plant cells.


1. Four narrow cups which can at least hold one cup of water

2. Measure cup of 1 cup, half a teaspoon, 1 teaspoon
3. Two Large (white, yellow or sweet) potatoes at least 2 inches long
4. Table salt
5. Cutting knife and cutting board
6. Gloves to protect your hands
7. Ruler


1. Label the 4 cups 1, 2, 3, 4
2. Add ½ tsp salt in cup 2
3. Add 1 tsp salt in cup 3
4. Add 2 tsp salt in cup 4
5. Add 1 cup of water to every cup
6. Mix salt with water by stirring with a spoon in the order of cup 2, 3 and 4
7. Cut one potato in half along the length
8. Cut into about 1 cm thickness
9. Cut into 1 cm strips
10. Cut the ends of the strips to 6 cm long
11. Put 3 strips in each cup
12. Measure length at ½h, 1h, 2h, 4h, 24h

Author: TeacherChunLei

Mrs. Chun Pfahnl is a Biology, Physical Science and Mandarin Chinese teacher at Colorado Early Colleges High School at Fort Collins. After obtaining B.S. in Biochemistry from Zhongshan University in Guangzhou, China, she worked with Guangdong Academy of Agriculture Sciences for 4 years before coming to US for graduate school at Smith College in Northampton, MA. After receiving M.A. in Biology, she worked as a Biomedical Scientist in 3 medical schools: University of Miami, University of Florida and Emory University for over 10 years. She also got M.S. in Computer Information Systems from University of Miami. She has taught Mandarin Chinese to school age students at all levels in local Sunday Chinese Schools for over 16 years and one year at CEC. She is currently teaching Biology and Physical Science at the high school. She has been living with her husband, two children and a dog in Colorado for 12 years, and enjoys gardening, skiing, hiking, traveling, reading, writing blogs in Chinese and volunteering in local and international communities. She loves to share her culture experiences and her passion of science with her students.