Ghost Balloons: Halloween STEM Experiment

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This spooky self-inflating ghost balloon will have your kids squealing with surprise and delight!

ghost balloon featured image

How do you explain the concept of a ghost to a toddler? You don’t want to start saying morbid things like “oh, it’s the spirits of dead people who haunt us from the beyond.” Talk about sleepless nights filled with nightmares! But what do you say to a toddler who keeps seeing images of ghosts posted everywhere for Halloween?

I have decided to go the simple route and explained that ghosts are these white creatures who can fly around because they have magic. Of course, anytime a toddler hears the word “fly,” he/she gets all excited and wants to know how. Well, here is a STEM activity that will show a toddler how a ghost can fly!


  • Baking soda
  • White distilled vinegar
  • Empty water bottle
  • Funnel (optional)
  • Balloon
  • Permanent marker
ghost balloon materials

Hopefully, you have all the supplies around the house and there is no need to go out shopping for them. Even if you do, you will easily be able to find other uses for baking soda or vinegar. I love using baking soda and vinegar to clear my drains – watching the bubbles fizzle is so fascinating!


  1. Fill the water bottle up with about 1” of vinegar.
  2. Draw a ghost face on the balloon with the permanent marker.
ghost balloon draw ghost face
  1. Fill the balloon with 3 tablespoons of baking soda. I used a funnel to get the baking soda into the balloon without too much spillage. *Tip: Make sure there are no clumps in your baking soda! The first time I tried this experiment the clumps clogged up my funnel and it look some muscle to push the clumps through.
ghost balloon funnel
  1. Carefully stretch the balloon over the mouth of the water bottle. Make sure the baking soda doesn’t spill into the bottle!
ghost balloon inflating
  1. Showtime! Lift the balloon so that it’s completely vertical, thus dumping all the baking soda inside into the vinegar.
  2. Watch the ghost balloon inflate!
ghost balloon inflated

How cool is this experiment! I love watching the balloon inflate, and it inflated a lot faster than I thought. You may want to keep a hand on the balloon while it is inflating to make sure the balloon doesn’t pop off the bottle and shoot vinegar everywhere.

You can play with the quantities of vinegar and baking soda if you wish – the more the baking soda and vinegar, the more carbon dioxide is generated, and the bigger the balloon should inflate. Just don’t go crazy because your balloon might explode or fly off and you would have a geyser on your hands!

How Does the Balloon Self-Inflate

If you have a curious 4 years old like mine, you may need to explain more about why the balloon can inflate with just the baking soda and vinegar. Well great, learning the science behind this experiment is the point of the STEM project! Basically, the acid (vinegar) and the base (baking soda) creates carbon dioxide gas when mixed together. Carbon dioxide causes bubbles to form in the water bottle and as the gas is released, the balloon starts to inflate.

Another question you may get is, how come the balloons don’t float? Well, carbon dioxide is heavier than air. Therefore, when you drop the balloon, it will fall to the ground instead of flying up in the air. Moreover, you will probably get some baking soda/vinegar mixture in the balloon and that would cause the balloon to be too heavy to float as well.

My kids had so much fun watching the ghost balloon inflate. Even though they are still unclear on what exactly is a ghost, I think this STEM experiment satisfied them for now. You can use different colored balloons to teach colors, and you can try experimenting with different balloon sizes. Overall, a super exciting experiment that consists of everyday household items and that is easy to set up. Win!

For more amazing Halloween STEM activities, check out:


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