SBI4U
Name:
Aerobic and Anaerobic Respiration Lab
In this lab activity, the time required to decolourize a solution of sodium hydroxide that is tinged
with phenolphthalein by exhaling into it by means of a straw, is recorded. Approximately 50 mL
of sodium hydroxide solution will be used each time. The time to decolourize is measured at rest
and after varying degrees of exercise. You will be working in groups of 3 or 4.
You will be writing a formal lab report for this lab.
Pre-lab [
/10]
1. What safety precautions must you use? Be specific!!! [
/2]
2. Draw a series of flow charts (with diagrams) that express what you need to do for this lab.
[
/3]
3. What is the reaction that occurs in this lab? Write both the word equation and the
chemical equation. (Hint: the carbon dioxide that is breathed out reacts with the water.
That compound will then react with the sodium hydroxide) [
/4]
4. Why do you see the colour change in phenolphthalein? [
/1]
SBI4U
Name:
Observations:
Complete the following chart with your observations of time (in seconds) to decolourize the
sodium hydroxide solution:
Group member’s name
Questions to Discuss [
At rest
After 2 minute of
mild exercise
After 2 minute of
vigorous exercise
/20]
1. What is the OVERALL balanced chemical equation for (a) aerobic respiration and (b)
anaerobic respiration in humans? Which reaction produces carbon dioxide? [
/5]
2. Why does the pink colour of the sodium hydroxide solution disappear after some time?
Explain this using chemical equations. [
/3]
3. What is the relationship between the time to decolourize and the amount of aerobic
respiration occurring? [
/2]
4. Using the data you have, answer the following questions. (Hint: graphing the data might help.
This graph may also be useful in your results section. Also, your results section should also
have the data that the answers to these questions are based off of)
a) Why is there a difference at rest between your group mates? [
/2]
b) Why did the time for decolourizing decrease after mild exercise? [
/3]
c) Why did the time for decolourizing increase after a longer period of exercise for some
people? [
/3]
5. Why would one continue to breathe heavily for some time after a vigorous exercise is
completed and the body is at rest? [
/2]