Where Does Carbon Dioxide Come From?
Let’s take a look at some of the sources of carbon dioxide in Earth’s atmosphere. You will use a pH indicator called Bromothymol Blue (BTB) which indicates the presence of carbon dioxide gas by turning from blue to yellow to orange. The more carbon dioxide that is introduced, the more orange the solution will become.
Question
What are some sources of carbon dioxide gas and how do they differ in concentration?
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Materials
- small trash bags
- straws
- tape
- dilute bromothymol blue solution
Procedures
Bromothymol blue (BTB) is a chemical indicator that changes color when carbon dioxide is added. Using the materials provided, test the level of CO2 from three different sources: room air, expressed lung air, and car exhaust.
Use the trash bags to collect both room air and car exhaust (carefully) then use straws to bubble each sample into the separate beaker of BTB and observe the color change. Repeat this process, using the straws, for expressed air from your lungs (blow bubbles into the solution).
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Observations
Which sample changed the color of the BTB the most? Did you expect this result? Why or why not?