BTB- bromthymol blue
solution (indicator)
 Used
to detect the
presence of carbon dioxide
Turns YELLOW if CO2 is
present
exercise
1. Same person exhaling
2. Constant breathing
Rate of change in BTB
3. Time of exhalation
A: Measure CO2 exhaled at rest
B: Measure CO2 exhaled after exercise
Measure time for BTB to change from blue to yellow
Measure no. of drops needed to change BTB back
• Practice breathing out to maintain constant exhalation
• Control accuracy of size of drops
EXPERIMENT
Will exercise affect the rate of change in BTB solution?
Independent variable
Dependent variable
(tested/changed)
(measured/result)
Control
Experimental/Test Group)
Student at Rest
Student Exercising
FAIR TEST (AVOID errors)
• same person tested
•constant breathing
•same breathing time
COLLECT DATA
If exercise is done
then, the rate of change of BTB will be (faster/slower)
because (more/less) carbon dioxide is produced
during exercise. When a person exercises, (explain
your understanding of breathing and respiration).
PART A. At Rest (three trials)
Blow air for
1 min (CO2)
Add drops of Ammonia
(base) until solution is
neutralized (changes
back to blue)
Record the time the solution
changes color.
Changes to YELLOW
if CO2 is detected
BTB
solution
CO2 + Water
forms an acid
PART B. After exercise (three trials)
Exercise for 1 min
Blow air for
1 min (CO2)
Add drops of Ammonia
(base) until solution is
neutralized (changes
back to blue)
Record the time the solution
changes color.
Changes to YELLOW
if CO2 is detected
BTB
solution
Ammonia
Acid
Base
Neutral
X no of drops of ammonia needed to
neutralize Acid in BTB solution