Download Measuring Differences in Carbon

Measuring Differences in Carbon-dioxide production
Bromothymol blue (BTB) is an indicator that changes color in the presence of acids or bases. It is
blue in the presence of a base and yellow in the presence of an acid.
Carbon-dioxide will alter the color of BTB in water (CO2 + H2O  H2CO3). You can use a titration
technique to compare the amount of carbon dioxide produced by a person at different levels of
physical activity.
SAFETY: BTB will stain clothes and skin. NaOH (sodium hydroxide) is corrosive and poisonous. Wear
safety goggles. Wash with soap and water immediately if your skin comes in contact with either
substance, and inform the teacher.
Titration procedure:
Use a straw to exhale air into the solution of BTB. Do not blow too forcefully, or it will bubble out.
Make sure you do not inhale. After the solution changes colors, practice changing it back again by
adding drops of sodium hydroxide. Swirl the solution after you add each drop—sometimes the color
change is delayed. The more drops of NaOH needed, the greater the amount of CO2 exhaled in the
container.
Your assignment:
How does the amount of carbon dioxide a person exhales change as a result of physical activity?
As a group, develop a hypothesis and design an experiment to test your hypothesis. You may use one
or all of your group members as guinea pigs. Take into account controls and variables. Enough data
should be taken to form conclusions. You may want to take averages or compare with other groups.
You will turn in a lab report that should follow the AP lab report format.
Measuring Differences in Carbon-dioxide production
Bromothymol blue (BTB) is an indicator that changes color in the presence of acids or bases. It is
blue in the presence of a base and yellow in the presence of an acid.
Carbon-dioxide will alter the color of BTB in water (CO2 + H2O  H2CO3). You can use a titration
technique to compare the amount of carbon dioxide produced by a person at different levels of
physical activity.
SAFETY: BTB will stain clothes and skin. NaOH (sodium hydroxide) is corrosive and poisonous. Wear
safety goggles. Wash with soap and water immediately if your skin comes in contact with either
substance, and inform the teacher.
Titration procedure:
Use a straw to exhale air into the solution of BTB. Do not blow too forcefully, or it will bubble out.
Make sure you do not inhale. After the solution changes colors, practice changing it back again by
adding drops of sodium hydroxide. Swirl the solution after you add each drop—sometimes the color
change is delayed. The more drops of NaOH needed, the greater the amount of CO 2 exhaled in the
container.
Your assignment:
How does the amount of carbon dioxide a person exhales change as a result of physical activity?
As a group, develop a hypothesis and design an experiment to test your hypothesis. You may use one
or all of your group members as guinea pigs. Take into account controls and variables. Enough data
should be taken to form conclusions. You may want to take averages or compare with other groups.
You will turn in a lab report that should follow the AP lab report format.