Estimating Lung Volume Worksheet for 13-Year-Olds — Middle School Science Lab

Instructions

Your lungs are amazing organs that allow you to breathe, talk, and live! The amount of air your lungs can hold is called lung volume or lung capacity. In this activity, you'll learn about different types of lung volumes and perform a simple experiment to estimate your own!

Key Terms to Know

• Tidal Volume (TV): The amount of air that moves in or out of your lungs with each normal, relaxed breath.
• Vital Capacity (VC): The maximum amount of air you can exhale after taking the deepest possible breath. This is what we will measure.
• Residual Volume (RV): The air that is always left in your lungs, even after you exhale as much as you can. This prevents your lungs from collapsing.
• Total Lung Capacity (TLC): The total volume of air your lungs can hold. (TLC = VC + RV)

Activity: Estimate Your Vital Capacity

We will use a balloon to get an estimate of your vital capacity. It's not perfectly accurate, but it's a great way to visualize the air you can push out of your lungs!

You will need:

• One round balloon
• A flexible measuring tape (or a piece of string and a ruler)
• A calculator

Procedure:

1. Gently stretch the balloon a few times to make it easier to inflate.
2. Take the deepest breath you possibly can, filling your lungs completely.
3. Exhale all the air from your lungs into the balloon in one single breath. Do not take a second breath.
4. Pinch the end of the balloon tightly to keep the air from escaping.
5. Use the measuring tape (or string and ruler) to measure the diameter of the balloon at its widest point. Measure in centimeters (cm). Record this in the data table below.
6. Release the air from the balloon. Repeat steps 2-5 two more times so you have three total measurements. Doing multiple trials helps make your results more reliable.

Data Collection & Calculation

Fill out the table with your measurements. Then, follow the steps to calculate your estimated Vital Capacity.

Step 1: Calculate the Average Diameter
Add the diameters from your three trials and divide by 3.
(Trial 1 + Trial 2 + Trial 3) / 3 = _______________ cm (Average Diameter)

Step 2: Calculate the Estimated Volume
To convert the balloon's diameter into a volume, we can use a simplified formula for the volume of a sphere. The volume will be in cubic centimeters (cm³). Note that 1 cm³ is equal to 1 milliliter (mL).
Formula: Volume (cm³) = (Average Diameter)³ ÷ 2
(This means: Average Diameter × Average Diameter × Average Diameter) ÷ 2

Your Calculation:
( _______ )³ ÷ 2 = _______________ cm³ (Your Estimated Vital Capacity)

Analysis & Critical Thinking

Answer the following questions based on the activity and what you've learned.

1. Why is it important to do multiple trials and calculate an average instead of just relying on one measurement?
2. List at least three factors that might affect a person's lung capacity. Why do you think these factors have an effect?
3. Why is this balloon method only an estimate of your vital capacity and not a perfectly accurate measurement? (Hint: Think about the shape of the balloon and the air transfer.)
4. The average Residual Volume (RV) for a teenager is about 1200 cm³. Using your estimated Vital Capacity (VC) from the experiment, calculate your estimated Total Lung Capacity (TLC). (Remember: TLC = VC + RV).

Vocabulary Reinforcement: Word Scramble

Unscramble the letters to spell out key terms from this lesson.

1. DITAL MEUVOL → ____________________
2. LATIV PACCYATI → ____________________
3. SIDERUAL VEMULO → ____________________
4. HATEREB → ____________________
5. SLUNG → ____________________

ANSWER KEY

Analysis & Critical Thinking (Answers)

1. Why is it important to do multiple trials and calculate an average?
   Doing multiple trials and taking an average helps to reduce the impact of any single error or unusual result. A single breath might not be your absolute maximum, or a measurement might be slightly off. Averaging gives a more reliable and representative result.
2. List at least three factors that might affect a person's lung capacity.
   Acceptable answers include:
   • Height/Size: Taller people generally have larger lungs and greater lung capacity.
   • Physical Fitness/Exercise: Athletes and people who exercise regularly often have stronger respiratory muscles and higher vital capacity.
   • Age: Lung capacity increases through childhood and adolescence, peaks in the early 20s, and then slowly declines with age.
   • Altitude: People living at high altitudes, where there is less oxygen, often develop a larger lung capacity over time.
   • Health/Smoking: Conditions like asthma or smoking can damage lung tissue and reduce lung capacity.
3. Why is this balloon method only an estimate?
   It is an estimate because: 1) The balloon is not a perfect sphere, so the volume formula is an approximation. 2) The balloon's own elasticity creates back-pressure, which might prevent you from exhaling all of your air. 3) It can be difficult to measure the diameter perfectly.
4. Calculate your estimated Total Lung Capacity (TLC).
   The answer depends on the student's own results. The student should show their work by adding their calculated Vital Capacity (VC) to the provided Residual Volume (RV) of 1200 cm³.
   Example: If a student's estimated VC was 3000 cm³, their calculation would be: 3000 cm³ + 1200 cm³ = 4200 cm³.

Vocabulary Reinforcement: Word Scramble (Answers)

1. DITAL MEUVOL → TIDAL VOLUME
2. LATIV PACCYATI → VITAL CAPACITY
3. SIDERUAL VEMULO → RESIDUAL VOLUME
4. HATEREB → BREATHE
5. SLUNG → LUNGS