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

Detecting Carbon Dioxide

The air we breathe is a mixture of several gases. One of these, carbon dioxide, is produced as a waste product by most living cells. Carbon dioxide also can be produced by a number of other means, including the mixing of a weak acid (vinegar) with sodium bicarbonate (baking soda).

Complete instructions for conducting activities in this slide set, including materials needed, setup instructions, student sheets (in English and in Spanish), answer keys and extensions, can be found in The Science of Air Teacher’s Guide, which is available free-of-charge at


1. In front of your students, inflate a large balloon. Ask them if there is anything inside the balloon. Stimulate a discussion about the contents of the balloon, leading them to the conclusion that the balloon contains air.

2. Tell students, Air consists of gases we cannot see or smell. However, we can tell gases are present in the balloon because they place pressure on the sides of the balloon and make it expand. Let the students feel the sides of the balloon.

3. Ask the students to observe as you place a few tablespoons of vinegar into the soft drink bottle. Next, using a note card that you have creased down the center, slide about one teaspoonful of baking soda inside the second balloon. Fasten the balloon over the mouth of the bottle, without letting the baking soda fall into the bottle.

4. Gently lift the balloon upward and let the baking soda fall into the vinegar at the bottom of the bottle. As carbon dioxide is produced inside the bottle, the balloon gradually will inflate. Challenge students to think about what might be causing the balloon to expand. Lead them to understand that mixing the two compounds produced a gas, known as carbon dioxide, which also is released from our bodies when we breathe out.

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