Most of you are already familiar with the classic erupting volcano science experiment. We’re basically doing that experiment, but with a little Halloween twist!

The “Puking Pumpkin”

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

  • One carved pumpkin

  • Baking soda

  • Vinegar

  • Food coloring

  • A large plastic juice jug or a bucket works too

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


  1. 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.
  2. 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!
  3. 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.
  4. Ready? Now slowly pour the vinegar into the pumpkin. Watch as your eruption starts and your pumpkin volcano looks like it is vomiting.
  5. 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.

The Giveaway

We wanted to make this even more fun by making a giveaway out of it and it’s really easy too! You don’t even have to do your own puking pumpkin experiment to enter, but you’ll get more entries if you do! The contest will open on Halloween night at 6 p.m. and go for two weeks. At the conclusion of the giveaway, we’ll pick 10 random entries to win a $25 gift certificate to Brick Circuit in downtown Albany.

Here are the 8 ways to enter:

1.) One entry for visiting and liking Mid-Valley STEM-CTE Hub on Facebook

2.) One entry for visiting and liking Brick Circuit on Facebook

3.) One entry for visiting and following Mid-Valley STEM-CTE Hub on Instagram

4.) One entry for visiting and subscribing to Mid-Valley STEM-CTE Hub on YouTube

5.) One entry for following Mid-Valley STEM-CTE Hub on Twitter

6.) One entry for following Mid-Valley STEM-CTE Hub on Pinterest

7.) FIVE ENTRIES for submitting a picture or video of your puking pumpkin on Instagram

8.) FIVE ENTRIES if you took park in Albany Parks & Recreations Trick-or-Treat Cruise at Bryant Park

That’s a total of 16 entries!

Happy Halloween and good luck!!!

Here’s our contest below. The more items you check off and do the more entries you get!