Sample procedure
- Open your lab notebook to take notes.
- Stretch the balloon by inflating it several times, then set it aside.
- Decide which ONE of the variables you will change in your setup that differs from the control setup:
1 packet of yeasttwo cubes (about 10mL) sugar250 mL water (111º F or 44º C)setup placed in room temperature air out of direct sunlight - Before you run the experiment comparing the three bottles, write a hypothesis. What do you think will happen in the three different bottles? Why?
- Label your bottle to indicate your changed variable. (In the example, the researcher changed the amount of sugar from 10 mL to 30 mL, and kept all the other values the same.)
- Put the water into the bottle.
- Put the yeast into the bottle (using a funnel, if available) and swirl it into the water.
- Put the sugar into the balloon. Stretch the mouth of the balloon over the opening of the bottle to make a tight seal.
- Pull the balloon up so that the sugar falls into the yeast solution.
10. Place the bottle in a warm place not in direct sunlight.
11. Wait. It may take 20 minutes or more before the balloon changes enough to notice.
12. Observe what happens in the bottle, and what happens to the balloon. Measure the circumference of the balloon at the end of the class session.
13. Record all your observations and measurements in your lab book.
14. Let your lab setup sit overnight.
15. Observe what happened in the bottle over the past 24 hours, and what happened to the balloon. Measure the circumference of the balloon.
16. Record all your observations and measurements in your lab book.
Note: Live yeast sometimes damage pipes. To clean up, pour your yeasty mix into a compost bin or somewhere outside. Or mix it with lots of water before draining.
