practical 4

• Use a cork borer to cut 5 potato cylinders.
• Trim the cylinders using a sharp knife and a ruler to the same length (about 3 cm).
• Accurately measure and record the mass of each cylinder.
• Measure 10 cm3​​ of the 1.0M sugar solution and transfer to the first boiling tube and label.
• Repeat step 4 for other concentrations of the solution and distilled water.
• Add one potato cylinder (of known mass) to each boiling tube.
• Prepare a table as seen below.
• Add one potato cylinder to each boiling tube, making sure the mass of each cylinder is known.
• Leave the cylinders in the boiling tubes for at least 15 minutes in a test tube rack.
• Remove the cylinders from the boiling tubes and dry them carefully by blotting with paper towels.
• Measure the mass of each cylinder and record your measurements in the table.
• Calculate the percentage changes for each cylinder.
• Plot a graph of change in mass (in g) against the concentration of sugar solution.
• Find the x-intercept to determine the concentration of sugar solution that is isotonic to the potato cells.
• Method for osmosis in a non-living system

  1. Tie one end of a visking tube with a piece of string.
  2. Pour some solution into the visking tube.
  3. Insert a capillary tube into one end of the visking tubing. Close the other end of the viskingtubing by tying with another piece of string.
  4. Use a marker to mark the initial water level in the visking tubing.
  5. Use a stand and clamp or other means to fix the position of the capillary tube, and immersethe visking tubing in a beaker of distilled water.
  6. Leave for 15 minutes.
  7. Note the difference in water level in the capillary.