Did you know that inflating and deflating a balloon can be as simple as heating up or cooling down the air inside the balloon!? Let’s jump in and learn how to do this fun Hot and Cold Balloon Experiment.
Get more fun and easy Atmospheric Pressure Experiments here!
My favorite thing about this cool science experiment is how easy it is to do at home with your kids…and they will love it!
Hot and Cold Balloon Experiment
- Empty plastic bottle
- 1 Bowl of Hot Water
- 1 Bowl of Cold Ice Water
How to Inflate a Balloon With a Bottle
- Fill a bowl with hot water and another bowl with ice cold water.
- Grab an empty plastic bottle and attach a balloon to the top of the bottle.
- Set the bottle in the bowl of cold water and the balloon will not inflate.
- Place the bottle in the bowl of hot water and watch as the balloon inflates!
- Now move the bottle back to the bowl of cold water to watch the balloon deflate again!
Step 1: Get a Bowl of Hot Water and a Bowl of Cold Water
For the best and most dramatic performance of this experiment you want your cold water to be as cold as possible, and your hot water to be as hot as safely possible.
I prefer to mix some ice into a large bowl with very cold water to make sure my ice water is very very cold. Then, using adult supervision, heat up some water in the microwave or on the stovetop in a separate large bowl or pot.
The water needs to be hot and steamy, but you don’t want it to be boiling either.
Step 2: Attach a Balloon to the Top of an Empty Bottle
Stretch the mouth of a large balloon over the opening of an empty plastic bottle. Sometimes it even helps to inflate the balloon first and deflate it to stretch the latex out a little bit before attaching it to the bottle.
It also helps to use your fingers to stretch the mouth and neck of the balloon out a little bit. The larger the balloon you use, the easier this step will be to slide the balloon mouth onto the bottle opening.
Step 3: Place the Bottle in the Cold Water
After you attach the deflated balloon to the bottle, place the bottle into the bowl of cold water and pay attention to what happens.
You should not notice much of a change with the balloon. In fact, it may even contract and shrink even smaller than before, and it certainly will not inflate in the cold water.
Step 4: Put the Bottle into Hot Water and Watch The Balloon Inflate
When you move the bottle and balloon from the cold water and place it into the hot water you should see a pretty dramatic change in the balloon. It should start to fill with air and inflate!
The balloon likely won’t get super big, because it needs more air pressure to stretch the latex a lot, but it will noticeably expand and get bigger in the hot water!
Step 5: Move the Bottle Back to the Cold Water
Put this experiment in reverse by moving the bottle from the hot water back into the cold water again. What do you think will happen to the balloon!?
You guessed it! The balloon will quickly shrink and deflate again once the bottle is placed in the bowl of cold water! This Baking Soda and Vinegar Balloon Experiment is another super cool way to inflate a balloon too!
Now it’s time to dive into the science behind how this hot and cold balloon experiment works!
How Does Temperature Affect the Size of a Balloon?
Generally speaking, the higher the temperature of the air inside a balloon, the larger and more inflated the balloon will become. On the flip side, the colder the air is inside the balloon, the balloon will shrink and deflate.
This shrinking and expanding of the balloon due to temperature is all thanks to a fancy scientific equation called the ideal gas law.
The Ideal gas law basically means as temperature increases, the volume of air inside the balloon does as well. This is because heat energizes the gas (air) molecules and they bounce into each other faster and faster.
As the bottle with the balloon attached is placed in hot water, the air inside the bottle heats up and the molecules move around faster and increase the volume and air pressure enough to inflate the balloon.
Then as the bottle is moved back into the cold water, the air molecules lose energy and slow down. They don’t bounce around as quickly and the volume and pressure decrease as the balloon deflates.
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