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## Gases Matter

Author(s): Nancy Moreno, PhD, Barbara Tharp, MS, and Judith Dresden, MS.
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Older students may enjoy working in small groups to mix the compounds to produce carbon dioxide themselves. When conducted by students, this activity will take about 30 minutes to complete. To conduct 6 small group activities, you will need the following materials: 6 soda bottles, 6 balloons, 1½ cups of vinegar, 6 teaspoons of baking soda, and 6 note cards.

To demonstrate how living organisms release carbon dioxide when they use food for energy, or to grow or reproduce, place one tablespoon of dry yeast, one teaspoon of sugar, and ¼ cup of warm water in a plastic soda bottle. Mix these ingredients by gently swirling the bottle. Attach a balloon to the top of the bottle and set the bottle aside for about 30 minutes. The balloon will begin to inflate as the yeast cells become active, use the sugar for food, and release carbon dioxide.

Ask students to suggest variations of the carbon dioxide investigation. They may wish to investigate, for example, the effect of temperature on the size of the inflated balloon.

To conduct this experiment, blow up a balloon and tie the end. Use a flexible tape measure to measure the balloon’s circumference at its widest part. If you do not have a flexible tape measure, you can simply measure the balloon’s width with a ruler. Next, gently submerge the inflated balloon in a bucket of ice cold water. After several minutes, remove the balloon from the water and quickly measure its circumference or width, as appropriate. The balloon should have decreased in size. Explain that lower temperatures cause gases to apply less pressure against the sides of a container, because their movement has slowed.

Students also may want to investigate how much more or less the balloon inflates if they add twice as much vinegar and baking soda to the mixture in the soda bottle.

Have students make the cylinder flyer described in the student storybook, Mr. Slaptail’s Secret (directions are provided at the end of the book). Talk about what supports or holds up the flyers as they soar through the air.

### National Institute of Environmental Health Sciences, NIH

The Environment as a Context for Opportunities in Schools
Grant Numbers: 5R25ES010698, R25ES06932

### Houston Endowment Inc.

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