Air Quality: Carbon Dioxide

Deborah Carlisleand

Steve Schneider

The Big Idea: Measuring Relative Amounts of CO2

Bromothymol Blue (BTB) changes color when CO2 is added.

BLUE TO YELLOW

YELLOW indicates an increase in the amount of CO2 gas.

When CO2 is added the solution becomes acidic.

What are we observing when BTB changes color?

In solution BTB can be in a “protonated” form or an “deprotonated” form. It is protonated in acidic solution.

H2CO3 H+ + HCO3- H+ +

CO32-

Yellow Blue

Where does CO2 come from?What will our students say?

Breath contains Carbon DioxideMolecules

Compare Controls

Making BTBEach Group make upRefer to Handout and Use Tap Water

Control 50mL of CO2

10 mL CO2 50 mL CO2

Calibration Scale

The ExperimentQuestion: Can we prove breath is about 5%

CO2?

Join your assigned group of 4 Create a calibration scale for BREATHPhotographImport photo and sample the colors in your

calibration scale using the line toolMake a graph of color intensity vs. percent

CO2

Calibration Scale % CO2

Control 1.25 % 1.75% 2.5% 50 mL breath w/exercise

Graph Data from image sampled with rectangle tool

GraphUse graph Excel or graph paper to make a

graph of your results

Results