Balloons are an exciting part of birthday parties and carnivals, but we can also use them for science. In this activity, we learn all about air pressure using just two materials!
What you need:
- 2 Liter Soft Drink Bottle
- Balloon
- Scissors
What you do:
First, insert the bulbous end of the end into the 2 liter soft drink bottle, with the open end of the balloon hanging out.
Next, fold the open end of the balloon over the opening of the bottle, so that it completely envelops it.
Have students make a prediction about whether or not they’ll be able to blow up the balloon while it is inside the bottle. Challenge students to try to blow the balloon up! Did they do it? Try poking a hole in the side of the bottle. Could they do it this time?
Questions to consider:
- Why couldn’t you blow the balloon up at first?
- Could you blow it up after you poked the hole? Why?
- What prevents the balloon from blowing up originally?
Why it works:
The balloon cannot be blown up within the bottle originally because of the air already inside. By trying to blow up the balloon, you are increasing the air pressure inside the bottle. The air has nowhere to escape to, however, so the balloon cannot inflate.
Once you poke a hole in the bottle, the air within the bottle is now able to be displaced and escape through it. This allows the balloon to inflate.
