Post on 03-Jan-2016
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