Air Quality: Carbon Dioxide Deborah Carlisle and Steve Schneider

The Big Idea: Measuring Relative Amounts of CO 2 Bromothymol Blue (BTB) changes color when CO 2 is added.

When CO 2 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. H 2 CO 3  H + + HCO 3 -  H + + CO 3 2- Yellow Blue

Where does CO 2 come from? What will our students say?

Breath contains Carbon Dioxide Molecules

Compare Controls

Making BTB Each Group make up Refer to Handout and Use Tap Water

Control50mL of CO 2

10 mL CO250 mL CO2

Calibration Scale

The Experiment Question: Can we prove breath is about 5% CO2? Join your assigned group of 4 Create a calibration scale for BREATH Photograph Import photo and sample the colors in your calibration scale using the line tool Make a graph of color intensity vs. percent CO2

Calibration Scale % CO 2 Control1.25 %1.75%2.5% 50 mL breath w/exercise

Graph Data from image sampled with rectangle tool

Graph Use graph Excel or graph paper to make a graph of your results

Results