Osmosis & Osmotic Concentration

Research Question:  What is the osmotic concnetration of specific plant tissues? 

Prepare Solutions

• 1. Make 2 liter of stock solution of 1M sucrose (C12H22O11) solution. Use can use the  Molecular weight calculator to determine the molecular weight. 

  2. Using this stock solution, make 200ml with the following concentrations: 0.8M, 0.6M,0.4M, and 0.2M.

Collect and Analyze your data

• 1. Cut six (6) 8-cubic centimeter (2 cm X 2 cm X 2 cm) blocks from a potato. The blocks should not include the skin.  You can approximate the size, but make sure that it is small enough to be submerged in the containers you are provided with. 

  2. Enter the mass of each cube in the data sheet

  3. Place one potato cube in each of the following solutions:  1.0M, 0.8M, 0.6M, 0.4M, 0.2M, and 0.0M sucrose

  4. Determine the mass of each cube near the end of the period. and enter the value  in the data sheet.

  5. Graph the percent change in mass as a function of time. 

  6. Estimate the osmotic concentration of the potato tissue by determining the average molarity of solution at which there is no change in mass.

  7. Enter your estimate in the quickwrite as directed by your instructor. 

  8. Repeat the process for celery, using dimensions of your choice.

Analyze the class data 

• 1. Examine a plot of the class data of percent change in mass as a function of time.

  2. Estimate the osmotic concentration of potato tissue from whole class data.

  3. Enter your estimate in the quickwrite as directed by your instructor. 

  4. What is the value of looking at whole-class data?