Constructing a lung model is an excellent way to learn about the respiratory system and how the lungs and the diaphragm work. Students need a plastic bottle cut in half, balloons, a piece of plastic from a shoppping bag, rubber band, drinking straws,...
Students tape the top of the balloons to the straws. Then put the straws down into the bottle and place the bottle onto a piece of plastic bag and use a rubber band to secure it tight to the bottom.
Now students can pull the diaphragm up and down and see the lungs expand and contract.
Check out this video.