Building a Model of an Air Sac

For your museum display, you will build several three–dimensional models. Here is just one idea for making a model.

Materials large white balloon thin plastic tubing scissors red, purple, and blue buttons pencil glue clear plastic tape sheets of red and blue construction paper Procedure Blow up a balloon. Tightly tie the base of the balloon so that the air does not escape. This balloon represents an air sac in the lungs. Wrap plastic tubing once around the balloon. Cut the tubing. Divide the tubing into thirds. Place a pencil mark at the first third and a pencil mark at the second third. Glue blue buttons end to end along the first third of the tubing. Then glue purple buttons end to end along the second third of the tubing. Last, glue red buttons end to end along the last third of the tubing. See the drawing. Tape the plastic tube to the balloon, as shown. From construction paper, cut out red and blue arrows. Tape these arrows to the balloon to show the exchange of oxygen and carbon dioxide inside the air sac. Make and attach these labels to the model: red blood cell, air sac, carrying carbon dioxide, carrying oxygen. On a sheet of paper write a title and description of what the model shows. With other students, brainstorm ways to improve the model.