This super easy and fun experiment is a great and safe way for kids and curious adults to learn about air pressure and how it affects everything from balloons to the weather around us. Let’s jump in and learn together with this Balloon in a Bottle Experiment.
Check out more fun and simple Plastic Bottle Experiments right here!
The best thing about this experiment is that you should be able to round up a few simple materials around your house to do it!
Balloon in a Bottle Experiment
This post may contain affiliate links. As an Amazon Associate, I earn from qualifying purchases.
How to get a balloon in a bottle
- Connect a large balloon to the opening of a clear, empty plastic bottle
- Push the deflated balloon into the bottle
- Try to inflate the balloon inside the bottle and see what happens
- Now use a needle or pin to poke a few small holes very close together on the bottle
- Repeat step 3 by trying to inflate the balloon inside the bottle.
- When the balloon has inflated inside the bottle, put your finger over the holes in the bottle, and observe what happens.
Step 1: Slide the mouth of a large balloon over the opening of a plastic bottle
Depending on what size of plastic bottle you have on hand for this experiment will determine what size of balloon you should use. I prefer to use a clean and empty 2-liter plastic bottle with a fairly large balloon.
These are the balloons like I like to use from Amazon. You can also use smaller balloons with a smaller water bottle, Gatorade bottle, or 20 oz soda bottle for this experiment as well.
The larger balloons just tend to work better and are much easier to stretch to fit over the opening of the plastic bottle.
Step 2: Push the deflated balloon into the bottle
Once you have connected your balloon to the bottle, go ahead and push the balloon into the bottle. You should be able to use your finger to do this, but if you have a large balloon and large bottle you might want to use the end of a wooden spoon or dowel to push the balloon inside.
Step 3: Use your hot air and try to inflate the balloon inside the bottle
Now it’s time for the hard part of blowing up the balloon inside the bottle! It seems like a pretty easy task to put the bottle up to your mouth and blow the balloon up inside the bottle right!?
Well if your lung capacity is anything like mine, you will find that inflating a balloon inside a bottle is a very very difficult and nearly impossible thing to do!
The difficulty of inflating a balloon in a bottle is thanks to the air inside the bottle not having an escape route to make room for the growing balloon. But there is a little trick we can do to help that air escape and the balloon to inflate!
Step 4: Grab a needle or a sharp pin to poke some holes in the bottle
Now that we have learned that it is pretty much impossible to inflate a balloon inside a bottle without a way for the existing air to escape, its time to create an escape route for that air in the bottle!
If children are participating in this experiment, please make sure to have an adult supervising while using the poky and sharp needles and pins for this step. Then go ahead and carefully poke a few very small holes close together on the bottle.
You will want to poke 4 or 5 holes in the bottle with a sharp needle, thumbtack, or sewing pin. Make sure the holes are very close together and in a location on the bottle that you can easily cover with your finger when holding the bottle.
Step 5: Try to inflate the balloon inside the bottle again
Repeat Step 3 and try to inflate the balloon inside the bottle now that you have put a few holes in the bottle. What happens!!!?
You should have a much easier time using the air in your lungs to inflate the balloon inside the bottle now that the air inside the bottle can escape as the balloon expands!
Step 6: Block the holes in the bottle with your finger while removing your mouth from the balloon
This is the coolest part of this balloon in a bottle experiment! While the balloon is still blown-up inside your bottle, slide your finger over the small holes you poked in the bottle. Then take your mouth off the end of the balloon and watch what happens!
You would expect the air inside the balloon to rush out of the opening of the bottle where the balloon is attached, but instead, the balloon somehow stays inflated inside the bottle!
The balloon will stay inflated inside the bottle as long as the holes on the side of the bottle remain plugged with your finger. If you remove your finger from the holes in the bottle, the increasing air pressure inside the bottle will then cause the balloon to deflate again.
Air pressure experiment with water bottle and balloon explanation
The fascinating science behind this balloon in a bottle experiment all depends on something we can’t see…air pressure! That’s right! The difference between the air pressure inside the bottle compared to the air pressure outside the bottle is what makes this experiment possible.
Let’s break this air pressure concept down a little bit further. In the wonderful world of weather high pressure always flows towards low pressure. This is why air is pushed out and away from a high-pressure weather system and the air is pulled in and towards a low-pressure system.
When relating this air pressure concept to this ballon in a bottle experiment we can visually see this process working thanks to the balloon inflating and deflating depending on the air pressure.
At first it is nearly impossible to inflate the balloon inside the bottle because the air inside the bottle is taking up too much space for the balloon to expand. When a few small holes are made in the bottle it lets the air escape and the air pressure drops.
The lower pressure created inside the bottle then allows the air with a higher pressure inside the balloon to expand and fill the empty space in the bottle.
Once the balloon is inflated inside the bottle, it will stay inflated if you cover the holes on the side of the bottle and release your mouth from the balloon thanks to a process called equilibrium pressure.
Equilibrium pressure occurs when the air pressure on the outside of the bottle is trying to become equal to the air pressure inside the bottle. Since the pressure in the bottle is now lower than outside the bottle, the higher pressure air on the outside will try to get inside the bottle.
If the holes on the side of the bottle are still plugged, then the only way for air to get into the bottle is through the opening of the bottle and into the balloon. This air pushing into the balloon trying to get into the bottle will keep it inflated.
Eventually, when you release your finger from the holes in the side of the bottle, the higher pressure on the outside with rush into the bottle. This will balance the air pressure inside the bottle and in the balloon and the balloon with naturally deflate.
How does air pressure influence cloud development?
Did you know we can also witness air pressure changes happening on a daily basis when we look in the sky and see clouds forming!? The higher a cloud gets in the sky, the lower the air pressure is surrounding it and the cloud will continue to grow and expand.
Check out this awesome experiment 3 Easy Ways To Make a Cloud in a Bottle if you want to make your own clouds and learn more about how clouds are formed!
If a cloud is in an environment of high-pressure, then the air pressure around the cloud will be higher than within the cloud and the cloud will actually shrink and eventually vanish.
This is the same reason why when you see a high-pressure symbol on a weather map you can usually expect sunny and clear skies, but when you see a low-pressure moving your way you better get ready for stormy, cloudy weather!