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Fuel for Living Things

Author(s): Nancy P. Moreno, PhD, Barbara Z. Tharp, MS, and Judith Dresden, MS.

Session 3: The Investigation

  1. Start a brief class discussion about yeast. Remind students that yeast is a living, microscopic, single-celled organism. Given the right conditions, it will grow and multiply. 

  2. Direct students to label one cup as “food” and the other as “no food.” Have them add about 1/2 cup of warm water and 1/2 teaspoon of yeast to each cup. Ask, Do you think the yeast cells have much to eat in the cup now? Help students understand that all living things need food to survive and grow.

  3. Ask, What do you think would happen if we added yeast food to one of the cups? Have students record their predictions. Then, have one person in each group add one teaspoon of sugar to the cup labeled “food,” and swirl or stir the solution gently.

  4. Direct each group to set its cups side-by-side and observe both cups every 5–10 minutes. Students should stir both cups (using separate stirrers) each time they make their observations. After a short time, students will observe that the yeast in the cup with sugar has begun to produce CO2 (turning the liquid foamy). 

  5. After 30–45 minutes, instruct students to pour small, equal amounts of the cabbage juice into both cups and stir the mixture. Ask them to observe the colors and record their observations. (The “FOOD” cup with yeast and sugar will be more pink than the “NO FOOD” cup without sugar.)


Funded by the following grant(s)

National Institute of Environmental Health Sciences, NIH

National Institute of Environmental Health Sciences, NIH

My Health My World: National Dissemination
Grant Number: 5R25ES009259
The Environment as a Context for Opportunities in Schools
Grant Number: 5R25ES010698, R25ES06932

Houston Endowment Inc.

Foundations for the Future: Capitalizing on Technology to Promote Equity, Access and Quality in Elementary Science Education