Audience-Pleasing Physical Models to Support CO2 Outreach

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Demo 1 — Chemistry of Burning [See materials and supplies]

Why is CO2 increasing in the atmosphere? Who/what is responsible?

Many people think that CO2 is “pollution” and that clean burning should be a way to eliminate greenhouse gas emissions.

Figure 1. Models made of Styrofoam balls are used to illustrate the chemistry of combustion.

In this demonstration, we review basic chemistry (figure 1) to show that producing CO2 is an inevitable waste product of burning any fossil fuel.

Set-up: prepare a box of different-sized Styrofoam balls painted to represent oxygen (largest ball, at least four), carbon (medium-sized ball, at least one), hydrogen (smallest ball, at least four). Cut several pipe cleaners into 1-inch lengths. Either a candle or an oil lamp is also needed.

Ask “What is in a hydrocarbon?” (Answer: hydrogen and carbon). One carbon attached to four hydrogens is methane, the simplest hydrocarbon molecule. Have participants make hydrocarbons by linking Styrofoam balls representing hydrogen (small) with carbon (medium sized) with the pieces of pipe cleaner.

Ask “How do we get energy from hydrocarbon?” (Answer: burn it, which means that oxygen must be added to the fuel in the presence of threshold heat.) If time allows, light a candle or small oil lamp using a match, and let these ideas sink in—hydrocarbons are from the candle or oil lamp, and oxygen is from the air. Point to or hold up the methane molecule, add two large Styrofoam balls (oxygen) to the medium-sized ball (carbon), and pull the hydrogens off (Say “pop” or “bang” as you do it to symbolize the release of energy). Then add two hydrogen balls to each of two oxygen balls. These actions represent combustion.

Ask “What are the products of fossil-fuel combustion?” Coach the audience to figure out the answer from the model (CO2 = carbon-di-oxide and H2O is water). Throw the molecules in the air to emphasize what happens to them under normal circumstances. People are usually surprised that water is released by combustion. Ask them to think about what they have seen coming out of tailpipes of cars or from smokestacks or chimneys on cool mornings. (White “smoke” is water vapor condensing.) Although people cannot see CO2, at least half as much CO2 as water is produced in most kinds of combustion.