Question 1 One of the end products of respiration is carbon dioxide, or CO2. In this activity, you’ll measure the amount of CO2 yeast produces when it is fermented in five different cups with the following contents:

Cup A: yeast and lukewarm water

Cup B: yeast, sugar, and lukewarm water

Cup C: yeast, sugar, and hot water

Cup D: yeast, sugar, and cold water

Cup E: yeast, sugar, and lukewarm water (covered with plastic wrap)

You’ll use a ruler to measure the amount of CO2, or foam, that forms in each cup. Do you think the amount of foam in the cups will differ? Write down your prediction.

Question 2

To prepare for the experiment, follow these steps:

Put one or two ice cubes in 1 cup of water. Chill the cup of water in the refrigerator for 1 to 2 hours. Remove any remaining ice when you take the water out of the refrigerator. This cup holds the ice-cold water.

Heat up three cups of water in the microwave for 15 to 20 seconds until they reach 100°F on the thermometer. If you heat the water too much, wait until the temperature drops to 100°F. These cups hold the lukewarm water.

Heat the last cup of water in the microwave until it reaches 212°F. This cup holds the boiling water.

Now line up the five glasses and label them A, B, C, D, and E. Then put the following contents in each glass:

Glass Contents

A 1 cup lukewarm water

B 1 cup lukewarm water and 1 tablespoon sugar

C 1 cup boiling water and 1 tablespoon sugar

D 1 cup ice-cold water and 1 tablespoon sugar

E 1 cup lukewarm water and 1 tablespoon sugar (this one will be covered with plastic wrap)

Use the spoon to stir the contents in glasses B, C, D, and E until the sugar dissolves. Then immediately add a packet of yeast to each glass. Wash the spoon and stir in the yeast. Cover the top of glass E tightly with plastic wrap.

Wait 15 minutes. Then measure the foam level in each glass in centimeters, as shown in the image.

glass of water containing yeast with foam on the top

Take measurements of the foam level every 15 minutes for 60 minutes. Record your measurements in the table.

Part B: Analyze and Extend

Question 1

How did your results match your predictions?