5 Easy Pumpkin Science Experiments and Activities to do this Fall

It’s here! Pumpkin season! We really can’t get enough of pumpkins this time of year – between decorating, carving and eating them, pumpkins are definitely the main characters of October.

In this article I’ve gathered some of our favorite pumpkin science experiments and activities – simple projects you can easily do at home.

1. Sink or Float Science Experiment

This is a fun STEM pumpkin experiment that explores buoyancy and fluid displacement. And it’s super simple – all you need are pumpkins and some water.

For this experiment, you will need:

• Miniature pumpkin
• Medium-sized pumpkin (a pie pumpkin works well)
• Small, halved pumpkin with insides removed
• Large container filled with water, a sink or bathtub

First, make your hypothesis. Do you think each pumpkin will float or sink, and why?

Now, test the pumpkins. One at a time, place each pumpkin in a large container of water – you can use a large bowl, storage bin, sink or even a bathtub. Record the results.

Your students may be surprised that even the larger pumpkin was able to float. The reason why pumpkins – and people, for that matter – float was discovered hundreds of years ago by the ancient Greek scientist named Archimedes.

Archimedes’ Principle, as it is called today, says that an object placed into a fluid will be pushed upwards by a force equal to the weight of the fluid it displaces. Since pumpkins are hollow inside, and less dense than the amount of water they displace, the water is able to push them up quite a bit, making them float.

Explore More: Sink or Float Predictions and Results Tracker

2. Pumpkin Investigation

Be a pumpkin investigator! Grab a pumpkin (any kind will do) and have your students note its outside characteristics (is it round, skinny, tall, short, smooth, bumpy, orange, green, etc?) by drawing a picture. They can also record its measurements, like weight and width.

Now carefully slice it open and describe its inside characteristics. This is also a good time to discuss pumpkin anatomy – the parts of a pumpkin.

Have your students guess how many seeds are inside their pumpkin. (This is a fun project to do with pumpkins of different sizes and varieties, if you have multiple students) Now, take out the seeds and count them. Were they close?

Explore More: Pumpkin Anatomy and the Parts of a Pumpkin

3. Pumpkin Volcanoes

Who doesn’t love a good, old-fashioned baking soda and vinegar project?

You will need:

• Mini pumpkins (one is sufficient but more is better!)
• Baking soda
• White vinegar
• Dish soap
• Food coloring (any color)
• Lemon juice (optional)

First, cut the tops off your pumpkins and scoop out the insides (save the seeds for the pumpkin sprouting activity, if you want!). Place the pumpkins on a large tray or table outside… things will get messy during the eruption!

Add 2 tablespoons of baking soda to the inside of each pumpkin. Add 1 teaspoon of dish soap, and some drops of food coloring. Stir it up well.

Now, time for the volcano! Pour vinegar into each pumpkin and watch them erupt! Once the eruption is finished, try it again with lemon juice, instead. How are the eruptions different?

What you’ve just observed is an acid (vinegar and lemon juice) + base (baking soda) chemical reaction, which produces carbon dioxide gas. The gas builds up quickly, pushing the liquid out of the pumpkin in a bubbly eruption. The dish soap traps the gas in bubbles, adding more foam to the eruption.  

4. Pumpkin Jack Life Cycle Activity

See the life cycle of a pumpkin in real time!

You will need:

• A large, plastic, clear container, thin enough to be able to cut off the top (a cheese ball or animal cracker
  container works well).
• A few handfuls of potting soil
• A pie pumpkin
• Duct tape or packing tape
• A spray bottle of water

First – and this is the fun part – carve a face into your pumpkin. The more you touch the outside and inside of the pumpkin, the better the experiment will work.

Next place a layer of potting soil in the bottom of your clear container. Place the carved pumpkin (with its insides! this is important) on top of the soil, spray it with water and tape up the top tightly.

Explore More: Life Cycle of a Pumpkin

Place the jar in a sunny area or sunny windowsill and watch as it decomposes throughout the winter. It should produce its own condensation and look wet and moldy. Once the pumpkin decomposes, the seeds will be left. When you’re ready to grow a new pumpkin, remove the layer of tape, cover the seeds with a bit of soil and keep them watered until they sprout. You can keep your plant inside near a sunny window until you’re ready to transplant it outside in late Spring.

For a simpler version of this activity, place your carved pumpkin outside in a cool, damp area and allow it to decompose outside during the winter. Water the seeds that are left behind in late springtime, and watch as a new pumpkin plant grows.

Pumpkin Jack is a great read-aloud book to go along with this activity!

5. Grow Your Own Pumpkin

How do pumpkins grow? Observe how a pumpkin seed grows into a pumpkin plant in real time.

First, dampen a paper towel and place it flat inside a plastic bag. Grab some pumpkin seeds from your investigation above, and place 2 seeds on top of the towel. Squeeze out most of the air in the bag and seal it, leaving a small gap for air at the top. You can label the bag at this point, if you wish. Using tape, hang the bag in a bright window.

Now watch as the seeds germinate. Make sure to keep the paper towel moist as the seeds sprout roots and shoots. Your students can keep a journal of their progress each day, if they wish.

Want more nature study goodness? Check out my Pumpkin Nature Study!