There are several things you can do with yeast. Yeast are responsible for alcoholic fermentation of glucose. Glucose is converted into ATP, alcohol and carbon dioxide gas. You can test the affect of temperature, or ph on the rate of fermentation. You can have an experimental set up with the variable you are testing--the independent variable. The dependent variable would be the rate of fermentation which could be observed by the amount of carbon dioxide produced. The control group would not get the independent or manipulated variable. If it is temperature for example, maybe the experimental group would have a higher or lower temperature than normal and the control group would be at room temperature. Balloons attached to the test tubes housing the yeast and sugar solution can capture the carbon dioxide. The amount of sugar left in the test tubes could indicate a slower or faster fermentation reaction. This can be tested by the Benedict's solution indicator for sugar test. You can even do an experiment about how yeast make bread dough rise under various experimental conditions--perhaps using different types of flour. Use your imagination and follow the scientific method for doing your experiment and subsequent lab report.