Want to know how much hot air middle school students have? Try this lung capacity lab. Students will be able to see how much air their lungs can hold!

The human body unit is once again upon us! Because I’m using a new curriculum this year, I’ve made some adjustments to how I go about teaching. However, a few labs are tried and true that I will definitely keep! This was one of them. It is so easy. Grab a balloon and a ruler for each student, and you’re set!

#### Warning:

Giving middle school students balloons does have some risks. Be prepared to hear many balloon squeals and other noises that sound like body functions. I warned the students in advance that no balloons should be released across the room.

#### Now to the lab:

Once students have received their balloon, they will use it to measure how much air their lungs hold. We compare the difference between vital capacity and tidal capacity of their lungs.

##### Vital capacity – the maximum amount of air the lungs can hold.

##### Tidal capacity – the normal amount of air that your breathe in and out.

#### Procedure:

- Students take a deep breath and blow up the balloon as much as they can with that one breath. Hold the balloon (do not tie it!) and measure the diameter with a ruler, recording this length.
- To find the volume, you can use the formula for the volume of a sphere (although the balloons aren’t perfectly sphere, this gives a pretty close measurement). Or, I give my students a graph that they can use to estimate the volume like this one, which is found l here at Biologycorner.com.
- Repeat this two more times, then find the average of all three.
- Next, students take in a normal breath and breathe it into the balloon. Be careful not to push too hard! This should be a normal breath.
- Record the diameter and then find the volume either using the formula or the graph.
- Repeat this two more times and then find the average diameter and average volume.

The average adult male has a vital capacity of a little more than 3000 cm3 and the average female’s vital capacity is about 2700 cm3. Of course, this also depends on height, weight, health and several other factors.

#### You can have students compare their lung capacities to their classmates. You can also ask follow up questions such as:

- What would you expect a professional athlete’s lung capacity to be? Why?
- What would you expect the lung capacity of someone who smokes to be?
- How might a musician’s lung capacity compare to others?

What a great way to lead into talking about health concerns and the importance of exercise!