Yielding Yeast, Part 2 -- April, 2003

1. As the yeast metabolize the sugar in the solution, carbon dioxide gas is produced (hence the foaming of the suspension). If they observe carefully, students should also be able to see tiny gas bubbles appearing to shoot from the bottom of the beaker toward the surface of the suspension. As CO₂ gas escapes, the net mass will decrease.
   
   
2. Students can repeat the experiment to test additional changes in activation conditions: water temperature, amount of sugar, pH, yeast type (i.e. compare "Quick-rising" to regular), etc. Alternatively, different lab groups can be assigned different test conditions. Challenge students to determine the ideal conditions for activation of yeast.
   
   
3. Special instructions for ScienceWorkshop users: The Ohaus balance is not compatible with the ScienceWorkshop line of probeware. To perform this experiment with the balance only, excluding the Temperature Sensor, follow the steps outlined below:
   
   
   1. Unplug the 500 interface from the back of your computer.
      
      
   2. In place of the interface, connect the Ohaus electronic balance to the computer using the 9-pin serial connector (RS232 cord) supplied with the balance.
      * Note: The cable is unidirectional; be sure to plug the labeled "scale" end into the balance. If the cable is plugged in the opposite way, the balance will blink continuously once the power is turned on and you will have to reverse the cable.
      
      
   3. Plug the power supply cord for the Ohaus electronic balance into an electrical outlet and turn the power on to the balance.
      
      
   4. Launch the DataStudio program and click the Setup button ( ) in the main toolbar to open the Experiment Setup window.
      
      
   5. Click the Change button ( ) and choose "PASPORT" when prompted by the dialog box that requests "Please Choose Data Source."
      
      
   6. Reopen the Experiment Setup window and click the Add Ohaus Mass button. The Ohaus balance icon will appear in the Summary window and a graph of Mass vs. Time will automatically appear.
      
      
   7. Close the Setup window and resize the display as needed.