When you take a deep breath your lungs fill with air and the muscle in front of your lungs, the diaphragm, also expand. This activity is a fun and simple representation of a lung.

Once you have assembled all of your supplies, tape the small balloon to one end of the straw. Tape just the neck of the balloon to the straw, leaving the more circular part of the balloon loose.

Make a hole in the bottom of the cup. The hole needs to be big enough to fit a straw through, but small enough that the straw will not slip out. You might want an adult to help make the hole. (With thicker plastic cups I have to use very pointy scissors or a knife.) Then slip the other end of the straw through the hole in the clear plastic cup.

Next, take the regular size balloon and cut off the neck. You will be cutting off a little less then half of the balloon’s length. We will be using the circular shaped balloon section. Stretch is a little the test the elasticity. We need to stretch the cut balloon over mouth of the cup (this can be very tough). I try to get it on one end first then stretch it around, like you would seal a Tupperware container.

The balloon stretched over the cup represents the diaphragm and the small balloon on the inside the lung. Pinch the middle of the stretched balloon and pull it out. As you pull the “diaphragm” you will notice the “lung” has expanded as well.

Now this isn’t a perfect model but it does illustrate how the lung and diaphragm expand and contract together. Sometimes people try blow into the straw to fill the “lung” with air but it’s hard to get the balloon the expand much.