This lab was a total fluke. I was looking for a fun demo to teach the VERY BORING topic of air pressure when I came across this Steve Spangler video. For those of you non-science nerds, he is the guru of classroom science experiments.
All this lab required was two water bottles, two balloons, one sharpie marker, and one pushpin. (Each lab group will need all of the supplies listed above). You ask the group to 1) label the bottles #1 and #2 2)make a hole in bottle #1 (with the push pin) and to leave the second bottle alone. 3) Place a balloon inside the neck of each water bottle. 4) try to blow up the balloons 5) Record the results.
Results: The balloon in bottle #1 will blow up easily, but the balloon in bottle #2 refuses to expand no matter how hard you blow.
Explanation: Even though the bottle is empty it is filled with air. When you place a balloon on the neck of the bottle you trap the air inside. When you blow up the balloon the trapped air pushes back on the balloon with pressure. The hole in bottle #1 allows the trapped air to leave the bottle and you to blowup the balloon.