The Puking Pumpkin!

This is a spooky Halloween twist on the classic volcano science project. This time around we are going to use a carved pumpkin as the vessel for our baking soda and vinegar explosion, resulting in a jack-o-lantern that looks like it’s vomiting.

Here are the supplies you’ll need for this project:

One carved pumpkin

Baking soda


Food coloring

A large plastic juice jug or a bucket works too

An outdoor space you don’t mind getting a little messy


First, carve your pumpkin! Take your pumpkin outside and set it on a surface that is easy to hose off. We used an upturned bucket.
If you haven’t already, take the top off your pumpkin. Now add baking soda (about 1/2 cup should be right, but adjust as necessary for best eruption). Be careful it doesn’t poof right out the mouth!

In the juice jug or bucket mix vinegar with some orange food coloring (or whatever color you want). We used about 2 cups of vinegar. This experiment does not require you to be exact. So let the kids experiment with ratios and play.

Ready? Now slowly pour the vinegar into the pumpkin. Watch as your eruption starts and your pumpkin looks like it is vomiting.
Grab more vinegar and you can do this over and over again! This is messy science at it’s best!!

The Science Behind the “Puking Pumpkin”

For this experiment, we are seeing a “puking pumpkin” or “eruption” when we add an acid (vinegar) to our base (baking soda) in our pumpkins in order to create a reaction. Pumpkins are not naturally acidic. You can tell this just by tasting them or using a pH test. Pumpkins need help to start their puking eruptions, so we add acid (vinegar) in order to create the chemical reaction that results in our pumpkin eruption.

Basically, it’s a very simple formula: Pumpkin + Baking Soda + Vinegar = Puking Pumpkin!

Or, if you want to get super scientific, you can use this one: CH3COOH (l) + NaHCO3 (s) = CH3COONa (l) + CO2 (g) + H2O (l) where:

  • Vinegar or Acetic Acid has the chemical formula CH3COOH.
  • Baking soda is a base also known as Sodium Bicarbonate and has the chemical formula NaHCO3.
  • During this reaction, the products are sodium acetate (NaC2H3O2). Sodium acetate is made of 1 sodium ion (NA), 2 carbon atoms (C), 3 hydrogen atoms (H), and 2 oxygen atoms (O). The other products are water (H2O) and carbon dioxide (CO2). Carbon dioxide is the gas that causes the bubbling during the reaction.



  • Download the companion worksheet here!
  • Looking for more project-based learning ideas? Click here!