12 Easy Pumpkin Science Experiments for Preschool and Kindergarten (Fun Fall STEM Ideas!)

When fall arrives, pumpkins take center stage in everything from pies to decorations. But did you know they’re also the perfect tool for hands-on science experiments? I love the fall season, and my daughter has so much fun when we incorporate the seasons into learning! If you’re homeschooling preschool or kindergarten, pumpkins offer a fun, seasonal way to explore STEM concepts while keeping little learners engaged.

In this guide, you’ll find easy, age-appropriate pumpkin science experiments that use affordable supplies, encourage curiosity, and fit seamlessly into your fall homeschool rhythm.

Why Pumpkin Science?

Pumpkins aren’t just festive—they’re also versatile teaching tools. By using pumpkins in your homeschool science lessons, kids can:

• Practice observation skills (noticing size, shape, and color differences).

• Explore basic math (measuring, weighing, and counting seeds).

• Learn about biology (life cycles and plant growth).

• Experiment with physics and chemistry (floating, sinking, and chemical reactions).

• Develop a natural sense of curiosity and wonder about the world around them.

Plus, kids are already excited about pumpkins in the fall—so it’s the perfect way to channel that seasonal enthusiasm into learning. Why Are Science Experiments Good For Early Childhood Learning? Find out what the Footsteps Early Learning Centre has to say here!

Supplies to Have on Hand

Before diving into experiments, here are some basic supplies that make pumpkin science easier:

• A few different-sized pumpkins (mini, small, medium, large)

• Bowls, spoons, and measuring cups

• A kitchen scale or bathroom scale

• Magnifying glass (check out our favorite one on Amazon!)

• Ruler or measuring tape

• Baking soda, vinegar, dish soap

• Toothpicks, markers, string

• Paper towels (things can get messy!)

Most of these items are things you already have in your homeschool or kitchen.

Here are The Best Living Books for the Fall Season if you’re looking for more seasonal reads for your little ones!

Pumpkin Science Experiments for Preschool and Kindergarten

Below are 12 engaging pumpkin science activities, each with step-by-step instructions, learning extensions, and simple ways to adapt for younger or older learners. My personal favorite is #10, so be sure to check it out!

1. Sink or Float? Pumpkin Edition

Concept: Buoyancy & density
What You Need: A tub of water and pumpkins of different sizes

Steps:

1. Fill a large bin, sink, or bathtub with water.

2. Ask your child: Do you think the pumpkin will sink or float?

3. Place the pumpkin in the water and watch what happens.

4. Try with pumpkins of different sizes.

Why It Works:
Even large pumpkins float because they’re hollow inside, filled with air pockets.

Learning Extension:

• Try with other fall objects (apples, gourds, pinecones) and compare results.

• Record predictions and outcomes in a simple chart.

2. Pumpkin Volcano

Concept: Chemical reactions (acid + base)
What You Need: Small pumpkin, baking soda, vinegar, dish soap, food coloring (optional)

Steps:

1. Cut the top off a small pumpkin and hollow out the seeds.

2. Add 2–3 spoonfuls of baking soda inside.

3. Add a squirt of dish soap and food coloring.

4. Pour vinegar into the pumpkin and watch it fizz and erupt.

Learning Extension:

• Explain that baking soda (a base) reacts with vinegar (an acid), releasing carbon dioxide bubbles.

• Try different amounts of vinegar or soap to see how the eruption changes.

If you want some really fun pictures of this experiment, check out this blog post by Steam Powered Family!

My daughter is younger, so I helped her with this experiment, and she had SO much fun with it. We got a little bit messy, but it was so worth it!

3. Pumpkin Life Cycle Exploration

Concept: Biology & plant growth
What You Need: Pumpkin seeds, soil, small pots, water

Steps:

1. Open a pumpkin and scoop out the seeds.

2. Rinse seeds and plant them in soil-filled cups or pots.

3. Place in a sunny spot, water regularly, and observe growth.

Learning Extension:

• Use a printable pumpkin life cycle chart (seed → sprout → vine → flower → pumpkin).

• Keep a growth journal with weekly drawings.

4. Pumpkin Dissection: What’s Inside?

Concept: Observation & anatomy of plants
What You Need: Pumpkin, knife (for adults), magnifying glass

Steps:

1. Cut open a pumpkin (grown-ups only).

2. Invite kids to scoop seeds and pulp.

3. Use magnifying glasses to inspect the strings, seeds, and skin.

Learning Extension:

• Separate seeds, pulp, and skin into piles.

• Count how many seeds are in your pumpkin.

5. How Many Seeds? Estimation & Counting

Concept: Math (estimation, counting, grouping)
What You Need: Pumpkin seeds, bowls, paper, markers

Steps:

1. Before opening the pumpkin, ask kids to guess how many seeds are inside.

2. Scoop out the seeds and count them in groups of 5 or 10.

3. Compare the actual number with their guess.

Learning Extension:

• Graph the number of seeds from different-sized pumpkins.

• Practice skip counting while sorting.

6. Pumpkin Decomposition Experiment

Concept: Nature cycles & decomposition
What You Need: Pumpkin, outdoor space, notebook

Steps:

1. Place a pumpkin outside in the yard.

2. Observe it over days or weeks as it begins to decompose.

3. Record changes with drawings or photos.

Learning Extension:

• Talk about how decomposition enriches soil.

• Compare pumpkins stored indoors vs. outdoors.

7. Pumpkin Boat Races

Concept: Engineering & buoyancy
What You Need: Hollowed-out pumpkin halves, tub of water, straws, paper sails

Steps:

1. Cut a pumpkin in half and scoop out seeds.

2. Place halves in water to see if they float.

3. Add straws and paper sails to make mini pumpkin boats.

4. Blow through straws to race boats across the tub.

Learning Extension:

• Discuss what makes some boats faster.

• Try adding weight (coins, small toys) to see if boats still float.

8. Pumpkin Stacking Challenge

Concept: Balance, gravity, fine motor skills
What You Need: Mini pumpkins, flat surface

Steps:

1. Provide several mini pumpkins.

2. Challenge kids to stack them as high as possible without falling.

3. Observe which shapes and sizes balance better.

Learning Extension:

• Discuss why rounder pumpkins roll and flatter ones balance.

• Record the tallest stack.

9. Pumpkin Temperature Test

Concept: Heat transfer & insulation
What You Need: Two pumpkins, thermometer

Steps:

1. Place one pumpkin inside (room temperature) and one outside (cooler air).

2. After a few hours, measure the inside pulp temperature.

3. Compare results.

Learning Extension:

• Discuss how pumpkin shells act as natural insulation.

• Try with other fruits or vegetables.

10. Pumpkin Catapult (STEM Challenge)

Concept: Physics & engineering
What You Need: Craft sticks, rubber bands, spoon, mini pumpkins (or candy pumpkins)

Steps:

1. Build a simple catapult with craft sticks and a spoon.

2. Place a candy pumpkin in the spoon and launch.

3. Measure how far it travels.

Learning Extension:

• Try changing angles or strength to see what makes pumpkins go farther.

• Record distances on a chart.

11. Pumpkin Float Candle Science

Concept: Buoyancy & light
What You Need: Small hollow pumpkin, tealight candle, water bowl

Steps:

1. Cut a pumpkin into a small bowl shape.

2. Hollow it out and place a tealight inside.

3. Float the pumpkin candle in a bowl of water.

Learning Extension:

• Talk about why the pumpkin floats and why the flame stays lit.

• Supervise carefully (fire safety!).

12. Pumpkin Taste Test (Cooked vs. Raw)

Concept: Sensory science & nutrition
What You Need: Raw pumpkin, cooked pumpkin, spoon

Steps:

1. Let kids taste a tiny bit of raw pumpkin (safe but bland).

2. Then taste cooked pumpkin.

3. Compare textures and flavors.

Learning Extension:

• Discuss why cooking changes food (heat breaks down fibers and releases sugars).

• Graph which version kids prefer.

Tips for Homeschool Success with Pumpkin Science

• Keep it hands-on: Preschool and kindergarteners learn best by touching, moving, and experimenting.

• Embrace mess: Science is messy—lay down a tablecloth or work outside.

• Encourage questions: Let kids lead with curiosity (“Why do you think it floats?”).

• Document discoveries: Use drawings, photos, or a science journal.

• Tie in other subjects: Reading Pumpkin Jack or From Seed to Pumpkin is a great way to blend literacy and science.

Pumpkin Books to Pair with Science Experiments

Here are some high-quality, well-loved picture books that pair perfectly with your pumpkin science lessons:

• From Seed to Pumpkin by Wendy Pfeffer

• Pumpkin Jack by Will Hubbell

• The Pumpkin Book by Gail Gibbons

• Pumpkin Circle: The Story of a Garden by George Levenson

• Too Many Pumpkins by Linda White

I love to tie in books with real-life experiences for my daughter—and I love to watch the connections she makes whenever we do this. It creates an opportunity for her to ask more questions and think a little deeper about the experiment that we did, which is so cool! These books add narrative context and help children visualize pumpkin life cycles and concepts.

Final Thoughts

Pumpkins aren’t just for carving or pie—they’re one of the best tools for hands-on learning in the fall. Whether you’re experimenting with buoyancy, exploring decomposition, or counting seeds, these activities spark curiosity while teaching science in a way little learners can grasp.

With just a few pumpkins and some simple supplies, your homeschool can enjoy an unforgettable season of discovery. We hope you and your little ones enjoy these experiments as much as we do!

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