What do four teaspoons of baking soda combined with three ounces of vinegar have in common with a running car?
They both emit carbon dioxide or CO2, a clear gas that is invisible to the naked eye, but is in the air all around the planet.
"Awareness starts with self," teacher Linda Cheney said as she encouraged her students to learn more about the effects of greenhouse gasses.
"As you learn more, you'll be able to talk intelligently about it as it comes up in conversation," Cheney said.
Her eighth-grade students at Tonto Basin School may only have riding experience in a running car, but they have hands-on experience with how greenhouse gasses are created and the potential effects of such gasses.
All "carbon-based-units" (as Cheney fondly calls her students) inhale oxygen and exhale carbon dioxide.
"Plant respiration releases more than 10 times the CO2 (as) released by human activity," reads one of many student-researched facts about greenhouse gasses listed on the classroom bulletin board.
"When scientists talk about the issue of weather changes, they're concerned that global warming is caused by human activities," read another.
The students have researched what greenhouse gasses do, now it is time to see them in action.
"What does fire require?" Cheney asked, using a lighted candle as an example.
"Air, fuel and heat," answered three individual students.
"If a flame is deprived of any one of those three things, it won't burn. How do you suppose I could use the flame to tell whether I had carbon dioxide?"
The suggestions of covering the flame, Cheney said, were proof that air was needed.
"So, when oxygen comes in to keep the fire lit, does it shoot back out carbon dioxide?" a student asked.
"Carbon dioxide, carbon monoxide and other gasses are the products of combustion," Cheney said.
CO2 molecules in the air are not concentrated enough to collect for experimentation, so each student tray was loaded with a clear long-neck bottle, a balloon, baking soda, vinegar, a few cups, BTB (Bromthymol Blue) solution, a straw and twist ties.
When Brett Goodwin added baking soda to the vinegar in Cheney's bottle, the mixture bubbled and to student "oohs" and "ahhs," CO2 smoke rapidly filled the glass.
Now it was the class' turn.
Each student group poured one-half ounce of blue-colored BTB solution into each of three cups.
One was the control. It was left alone and it did not change color.
Students used an air pump to add air to the second.
Although the "air" cup did not change color for most of the groups, one student thought the BTB had turned a lighter shade of blue.
If the class had been doing the experiment in Phoenix, they predicted the BTB might have been an even lighter blue, or green, because there are more vehicles and industry there, while Tonto Basin has more plant life. To know for certain, Cheney told them they would have to go to Phoenix and test the air.
Using a balloon, students added baking soda to vinegar and collected the CO2.
The faster they were able to place the balloon on top of the bottle, the higher the concentration of CO2 collected.
From the balloon, they added gas to the third cup of BTB solution. It turned varying shades of yellow and green, depending on the amount of gas.
According to the research students have been doing for several weeks, they have discovered that scientists do not agree on the percentages of emissions (carbon dioxide, methane and nitrous oxide) contributing to atmospheric warming. Scientists use measurements of average global temperatures and concentrations of carbon dioxide from the Ice Age, 140,000 years ago, to determine how warming could affect human health and ecological systems and come to the same conclusions.
But students are learning to research diverse opinions and draw their own conclusions.