Yielding Yeast -- March, 2003


Teacher Hints:

  1. Demonstrate proper technique for filling a cuvette so that it contains a representative sample of the original solution, including particulate matter, but so that bubbles are not present to interfere with the turbidity measurement. Remind students that the cuvette glass must be clean for accurate results.

  2. For accurate results, it is crucial that the turbidity of the sample be measured as quickly as possible after the yeast are activated. Remind students to calibrate the Turbidity Sensor prior to working with the yeast. Instruct them to quickly stir the yeast into the warm sugar water and be ready to dilute the solution immediately for use in the Turbidity Sensor.

  3. You may wish to have students repeat the experiment using different activation conditions: colder or warmer water, more or less sugar, etc. Alternatively, different lab groups can be assigned different activation conditions. Challenge students to determine the ideal conditions for activation of their yeast.

  4. Dark-colored or very opaque solutions will not be measured accurately by the Turbidity Sensor. Adjust the dilution of the initial sample as needed for best results.

  5. Remind students that turbidity is a dynamic phenomenon, and that particles will continue to move and settle within the solution even as the cuvette is inserted into the sensor. The turbidity reading will continue to decline and fluctuate as particles settle out of solution.

  6. Data runs can be easily renamed to keep track of testing conditions. Click once on "Run #1" in the Summary window, pause, and then click again. The run name will become editable: type in "activated yeast" or other description, then click elsewhere on the screen. (For more detailed instructions on renaming data runs, refer to DataStudio's January 2003 Tip of the Month, available online at www.pasco.com/datastudio_tips.)