Saturday, April 7, 2012

breathy experiment

How much air do we breathe in and out for every breath?  There is a fairly simple way to measure the amount of air that you exhale in one breath.  You will need:
a vessel (a plastic milk jug would work great, but we used a glass jug)
a measuring cup 
a large container (bowl, pot or washtub)
clean flexible tubing of some sort or bendy straws 
tape and a marker
We calibrated the jug by adding one cup of water at a time and marking that amount on the tape.  Our vessel held 8 1/2 cups.

The large container should be filled with a couple of inches of water.  If doing this experiment inside, make sure that your container can hold all of the water in your vessel as well as this initial amount of water, or you might have an overflow.
*photo by Sylvia
 Completely fill your vessel and insert one end of the tubing.  If using bendy straws you could attach two together with duct tape to get a longer air-tight tube.  After covering the top of the vessel with your hand, invert it into the container and immerse the opening into the water before letting go.  Continue holding the vessel upright with your other hand.  All of the water should stay trapped in your jug.

After completely filling your lungs with a deep breath, blow into the tubing until all of your air is expelled.  Your breath will displace the water in the jug and you can measure the remaining water level against the marks on your tape.
*photo by Papa
 Sylvia blew out 3 1/2 cups of air, Camille blew out 7 cups, and I blew out 8 1/4 cups.

 The average total lung capacity for humans is 4 to 6 liters (about 17 to 25 cups), but only about a third of this is used during normal, non-strenuous activity.  You could try this experiment again using an average inhalation and exhalation to compare the difference between this and a deep breath with forced exhalation.

My girls were surprised to see how much air they could expel, and we talked about the fact that no matter how hard you exhale there is still residual air in the lungs.  So while this doesn't show total lung capacity, it can be a fun visual to see the volume of exhaled air.

*The inspiration for this experiment came from the book Head to Toe Science.

I linked up with Stephanie today for Saturday's Artist.  Science can be art, of course, ... right?


  1. looking at your pic i want my dreads back, waaaah!

  2. That is a fun experiment! My boys, especially Quentin would really like it.

  3. Pinned this one! Looks like fun!! :)


I love hearing what you have to say. Leave a comment?