Name
Period
Date
BTB Exercise Lab
Background: Bromothymol Blue (BTB) is a
pH indicator. In other words, it determines
how acidic or how basic the substance is.
It does this by changing colors.
Pre lab question:
1. A scientist finds that after placing three
drops of bromothymol blue, the solution
turns yellow. Does this indicate there is
carbon dioxide present in the solution?
How did you know?
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Problem Statement: What is the effect of exercise on the rate of cellular respiration?
Directions: With your team, identify the variables of this experiment.
Independent Variable
Dependent Variable
Constant Variable
Procedures:
1. Partner 1 is ready with a timer
2. Partner 2 exhales into straw inserted in
the test tube of bromothymol blue
3. Once the bromothymol blue turns
YELLOW, Partner 1 stops the timer
4. Record the time in seconds in the data
table below
5. Partner 1 does 20 jumping jacks and
runs in place for 2 minutes
6. Partner 1 times while Partner 2 blows
into the test tube until it turns YELLOW
7. Record the time in seconds in the data
table below.
Results:
Time for color
change
(seconds)
Control (at rest)
Trial 1 (after physical
activity)
On the right, make a bar graph with your results. Be sure to label the title, x axis, and y axis.
Analysis Questions:
1. Write the overall chemical equation for cellular respiration. Label the products and reactants.
2. What is the main purpose of cellular respiration?
3. Why was Bromothymol Blue used as an indicator for cell respiration?
4. How long did it take for the bromothymol blue to turn yellow without exercising? How long did it take for
the bromothymol blue to turn yellow with exercising?
5. Explain the relationship between physical activity and cell respiration.
6. Using the chemical equation for cellular respiration, explain how physical activity increases the rate of
cell respiration. Support your answer with your data.
7. Explain why after intense physical activity does a person feel cramps. (Hint: what did their muscles make)