Slide 1 / 16
This material is made freely available at www.njctl.org and is intended for the non-commercial use of students and teachers. These materials may not be used for any commercial purpose without the written permission of the owners. NJCTL maintains its website for the convenience of teachers who wish to make their work available to other teachers, participate in a virtual professional learning community, and/or provide access to course materials to parents, students and others.
Click to go to website: www.njctl.org New Jersey Center for Teaching and Learning Progressive Science Initiative
http:/ / njc.tl/ 16
Slide 2 / 16
BIOLOGY Osmosis Lab
www.njctl.org Membranes & Enzymes
http:/ / njc.tl/ 6
Slide 3 / 16
What determines the direction of osmotic flow? Hypotheses:
Problem Slide 4 / 16 Materials
6 clear cups 6 pieces of 15 cm Dialysis tubing 12 pieces string 10 cm in length 1 plastic medicine cup 10 ml Distilled water 10 ml 0.2 M Sucrose solution 10 ml 0.4 M Sucrose solution 10 ml 0.6 M Sucrose solution 10 ml 0.8 M Sucrose solution 10 ml 1.0 M Sucrose solution 1 Marking pencil Labeling tape Calculator Paper towels Balance Enough distilled water to cover dialysis tubes in cups
Slide 5 / 16 Procedure
Step 1 Obtain six plastic cups and number them from 1 to 6. Step 2 Obtain six pieces of soaked dialysis tubing. Open one end
- f each tube by gently rubbing it in between your fingers. Tie one
end of each tube off with a piece of string. Step 3 Using a measuring cup, measure out 10 ml of each of the six solutions. Step 4 Pour the contents of one solution into the first dialysis tube and tie it closed with another piece of string. Continue to do the same thing with the remaining five solutions. Make sure to rinse
- ut the measuring cup in between solutions.
Step 5 Rinse the outside of each dialysis tube with running water and then use paper towels to dry the outside of each bag. Step 6 Record the initial mass of each bag in Table 2.
Slide 6 / 16
Step 7 Place the appropriate dialysis tube into each of the numbered cups and fill each cup with enough distilled water to completely cover each tube. Step 8 Begin timing for a total of 30 minutes. Step 9 After 30 minutes have passed, remove each dialysis tube from its container and gently blot any excess water from its surface. Step 10 Record the final mass of each bag in Table 2 and then calculate the percent change in mass for each tube. % Change = (Final Mass – Initial Mass)/Initial Mass x 100. Record the class averages for % Change in Mass in Table 3. Step 11 Construct two graphs. The first graph will be of your group’s % Change in Mass. The second graph will be the class average of the % Change in Mass for each dialysis tube.
Procedure