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# ___ Lab – Tidal Volume and Lung Capacity
Problem: What factors can affect lung capacity?
Introduction: When you inhale, air rushes into your lungs. The amount of air that rushes in during a normal
breath is called the tidal volume. Your lungs have the capacity to accept a much larger volume of air than
you normally inhale. For example, you might be asked to take a deep breath during a medical exam.
Scientists use the term vital capacity to describe the largest volume of air that you can exhale after you take
a deep breath.
In this lab, you will measure tidal volume and vital capacity. Then you will design an experiment to
investigate a factor that can affect vital capacity.
Skills Focus: Measure, Form a Hypothesis, Design an Experiment, Interpret Graphs
Materials: round balloons, metric ruler, meter stick
Safety: Do not test your vital capacity if you are ill or have difficulty breathing. If at any point you feel faint
or dizzy, stop what you are doing and sit down. Ask your partner to inform your teacher of the problem. Do
not handle balloons if you are allergic to latex. You and your partner must use different balloons.
Pre-Lab Questions: (3 pts.)
1. Control Variables. What is the difference between the procedures in Part A and Part B?
2. Design an Experiment. Why must you use round balloons for this experiment?
3. Predict. Which do you think will be greater – your estimated vital capacity or your measured vital
capacity? Why?
Procedure & Data:
Part A: Tidal Volume (2 pts.)
1. Stretch a round balloon lengthwise several times
Data Table 1: Tidal Volume
2. Stand up and inhale normally, then exhale normally,
but quickly into the balloon. Immediately pinch the
Trial
Diameter (cm) Volume (cm3)
balloon shut so that no air escapes.
3. Keep pinching the balloon as you place it on a flat
1
surface. Have your partner measure the diameter of
2
the balloon at its widest point as shown in figure 1.
Record the measurement in Data Table 1.
3
4. Allow the balloon to deflate. Repeat Steps 2 and 3
two more times.
Mean
5. Calculate the mean for the measurements from the
three trials and record your answer in the data table.
6. On the graph in Figure 2, balloon diameter in centimeters is plotted against volume in cubic
centimeters (cm2). Use the graph to find the volumes that correspond to your diameter
measurements. Record your results in Data Table 1.
Part B: Vital Capacity (2 pts.)
Data Table 2: Vital Capacity
7. Stand up and take as deep a breath as possible.
Then, exhale as much air as you can form your lungs
Trial
Diameter (cm)
Volume(cm3)
into the balloon. Immediately pinch the balloon shut
so that no air escapes.
1
8. Keep pinching the balloon as you place it on a flat
surface. Have your partner measure the diameter of
2
the balloon at its widest point. Record the
measurement in Data Table 2.
3
9. Allow the balloon to deflate. Repeat Steps 6 and 7
Mean
two more times.
10. Calculate the mean for the measurements from the
three trials and record y our answer in the data table.
11. Use Figure 2 to find the volumes that correspond to your diameter measurements. Record your
results in Data Table 2.
Figure 1 How to measure the diameter of the
balloon
Source: http://mvhigh.net
Figure 2 Lung volume verses balloon diameter
Part C: Estimating Vital Capacity (2 pts.)
12. You can use the meter strips taped on the door to
Data Table 3: Estimated Vital Capacity
measure your height in centimeters. Or you can
convert your height in inches to centimeters by
Height (cm)
multiplying the number of inches by 2.54. Record
your height in Data Table 3.
13. To convert your mass in pounds to kilograms,
Weight (kg)
multiply the number of pounds by 0.454. Record
your weight.
Surface Area (m2)
14. Use Figure 3 to estimate the surface area of your
body. Find your height on the scale on the left. Find
Vital Capacity (cm3)
your mass on the scale on the right. Use a ruler to
draw a straight line between those points. The
location where the line crosses the middle scale is your estimated surface area.
15. To calculate the estimated vital capacity of your lungs, multiply your surface are in square meters by
the ratio of vital capacity to surface area. Based on research, the ratio is 2000 cubic centimeters per
square meter for females. For males, the ratio is 2500 cubic centimeters per square meter. Calculate
and record your answers in Table 3.
Figure 3 Estimated surface area based on height and mass
Part D: Design Your Own Lab Would the results of your lab have been different if you were seated?
Would your posture when seated affect the results?
16. Form a Hypothesis How will you changing the position of your body affect your vital capacity?
Record the hypothesis you will test to answer this question. (2)
Hypothesis:
17. Describe Your Plan Describe the procedure you will use to test your hypothesis. How will you
modify the procedure from Part B? What variables will you need to control during your trials? (3)
Experimental Plan:
18. Construct a data table in the space below. Make as many rows for recording data as the number of
trials you plan to do. Include a row for recording the mean of your trials. (2)
Analyze and Conclude:
1. Analyze Data How did you estimated vital capacity compare with your measured vital capacity?
Was your prediction in Pre-lab Question 3 correct? (1)
2. Draw Conclusions What could have caused any difference between the estimated value and the
measured value? (2)
3. Design an Experiment Why is it important to do more than one trial when making measurements?
(1)
4. Infer In Step 14, why did females and males use different ratios to calculate estimated vital capacity?
(1)
5. Perform Error Analysis In Part A, why might the volume in the first trial be smaller than in the
second and third trials? How could the procedure be adjusted to avoid this results? (2)
6. Predict How would smoking affect lung capacity, and why? (2)