STEM Activities for Preschoolers: Simple Science Experiments That Wow

Ever seen your preschooler’s eyes light up with wonder? That magical moment when they discover something new about their world? That’s the power of STEM (Science, Technology, Engineering, and Math) in action!

As parents and educators, we know early exposure to STEM concepts builds critical thinking skills and nurtures natural curiosity. But let’s be honest—the idea of “teaching science” to 3-5 year olds can feel overwhelming. Where do you start? What materials do you need? And how do you make complex concepts accessible to young minds?

Good news! You don’t need a laboratory or a science degree to introduce your little ones to the wonders of STEM. In fact, some of the most impactful science experiences for preschoolers use simple materials you already have at home.

In this article, I’ll share 15 simple yet jaw-dropping science experiments that will captivate your preschooler’s imagination while building a foundation for STEM learning. Each activity includes:

• Easy-to-find materials
• Simple step-by-step instructions
• The “wow factor” that will amaze your little scientist
• The science behind the magic (explained in preschooler-friendly terms)

Let’s dive into these accessible experiments that transform everyday moments into extraordinary learning opportunities!

Why STEM Matters for Preschoolers

Before we jump into the experiments, let’s talk about why early STEM exposure matters. According to the National Science Foundation, children who engage with STEM concepts before age 5 develop stronger problem-solving skills and show greater interest in STEM subjects later in life.

But here’s what’s really important: preschoolers are natural scientists! They’re constantly observing, questioning, and experimenting with their world. Our job isn’t to “teach” them science—it’s to provide opportunities that nurture their innate curiosity and help them make sense of what they observe.

As Dr. Rachel White, developmental psychologist and early childhood researcher, explains: “When preschoolers engage in hands-on STEM activities, they’re not just learning scientific facts—they’re developing critical thinking skills, building vocabulary, and gaining confidence in their ability to understand the world around them.”

Now, let’s get experimenting!

Water & Liquid Science Experiments

1. Walking Rainbow

Materials:

• 7 clear cups or jars
• Paper towels
• Food coloring (red, yellow, blue)
• Water

The Wow Factor: Watch as water “walks” up paper towels and colors mix themselves to create a beautiful rainbow!

Instructions:

1. Arrange the cups in a row.
2. Fill alternate cups with water (1st, 3rd, 5th, and 7th).
3. Add red food coloring to the 1st cup, yellow to the 3rd, and blue to the 5th.
4. Fold paper towels lengthwise and place one end in a cup with colored water and the other end in an empty cup.
5. Wait and watch the magic happen over several hours!

The Science: This experiment demonstrates capillary action—the ability of liquid to flow upward against gravity in narrow spaces. The paper towel fibers act like tiny straws, pulling the colored water up and over into the empty cups. When different colors meet in the middle cups, they create new colors (red + yellow = orange, yellow + blue = green, etc.).

Preschooler-Friendly Explanation: “Water is like a tiny climber! It can climb up the paper towel even though it usually falls down. When the different colored waters meet, they mix together to make new colors—just like when you mix your paints!”

2. Magic Milk Explosion

Materials:

• Shallow dish
• Whole milk (works better than skim)
• Food coloring (various colors)
• Dish soap
• Cotton swab

The Wow Factor: Watch colors dance, swirl, and explode across the surface of milk with just a touch of soap!

Instructions:

1. Pour enough milk to cover the bottom of a shallow dish.
2. Add drops of different food colors spread out across the surface.
3. Dip a cotton swab in dish soap.
4. Touch the soapy swab to the milk’s surface and watch the explosion of color!

The Science: Milk contains fat molecules and proteins. When dish soap is added, it breaks up the fat molecules, causing the milk to move. As the milk moves, it carries the food coloring with it, creating a swirling color explosion.

Preschooler-Friendly Explanation: “Milk has tiny bits of fat in it. Soap chases away the fat, making everything move around really fast. The colors are just going along for the ride!”

3. Ocean in a Bottle

Materials:

• Clear plastic bottle with cap
• Water
• Blue food coloring
• Vegetable oil
• Small shells, glitter, or tiny plastic fish (optional)

The Wow Factor: Create a portable, never-ending ocean wave that mimics the real thing!

Instructions:

1. Fill the bottle about 1/3 with water.
2. Add a few drops of blue food coloring and stir.
3. Add shells or glitter if desired.
4. Fill the rest of the bottle with vegetable oil, leaving a small air gap at the top.
5. Secure the cap tightly (you may want to hot glue or super glue it for safety).
6. Tip the bottle side to side and watch the waves form!

The Science: This experiment demonstrates density and immiscibility (when liquids don’t mix). Water is denser than oil, so it sinks to the bottom. The two liquids don’t mix because water molecules are polar (attracted to each other) while oil molecules are non-polar.

Preschooler-Friendly Explanation: “Water and oil are like cats and dogs—they just don’t want to mix! The water is heavier, so it stays at the bottom. When you tip the bottle, the water moves like real ocean waves!”

Air & Pressure Experiments

4. Balloon Rocket Race

Materials:

• String (about 10-15 feet)
• Straws
• Tape
• Balloons
• Clothespins or clips

The Wow Factor: Watch balloons zoom across the room on a string pathway!

Instructions:

1. Thread the string through a straw.
2. Tie the string between two points (like chairs or doorknobs).
3. Blow up a balloon but don’t tie it—use a clothespin to keep the air in.
4. Tape the balloon to the straw on the string.
5. Remove the clothespin and watch the balloon rocket along the string!

The Science: This demonstrates Newton’s Third Law of Motion: for every action, there is an equal and opposite reaction. As air rushes out of the balloon in one direction, it propels the balloon in the opposite direction.

Preschooler-Friendly Explanation: “When air zooms out of the balloon, it pushes the balloon forward—just like when you let go of a balloon and it flies around the room!”

5. Tornado in a Bottle

Materials:

• Two plastic bottles of equal size
• Water -Duct tape or a tornado tube connector
• Glitter or food coloring (optional)

The Wow Factor: Create a spinning vortex that looks just like a tornado!

Instructions:

1. Fill one bottle about 2/3 full with water.
2. Add glitter or food coloring if desired.
3. Attach the second bottle to the top of the water-filled bottle (mouth to mouth) using duct tape or a tornado tube connector.
4. Flip the bottles so the water is in the top bottle.
5. Swirl the top bottle in a circular motion and watch the tornado form as water flows to the bottom bottle!

The Science: The swirling motion creates a vortex as air from the bottom bottle moves up through the center while water from the top bottle flows down around the sides. This demonstrates centripetal force and fluid dynamics.

Preschooler-Friendly Explanation: “When you spin the water, it makes a tiny whirlpool. Real tornados are giant spinning air columns—just like our bottle tornado is a spinning water column!”

6. Magical Inflating Balloon

Materials:

• Empty plastic bottle
• Balloon
• Baking soda (2-3 tablespoons)
• Vinegar (1/4 cup)
• Funnel

The Wow Factor: Watch a balloon inflate itself without anyone blowing into it!

Instructions:

1. Using a funnel, pour the baking soda into the empty balloon.
2. Pour vinegar into the bottle.
3. Carefully stretch the balloon over the bottle opening, keeping the balloon’s contents from falling in.
4. When ready for the reaction, lift the balloon to dump the baking soda into the vinegar.
5. Watch the balloon inflate!

The Science: When baking soda (sodium bicarbonate) and vinegar (acetic acid) mix, they create a chemical reaction that produces carbon dioxide gas. This gas fills the balloon, causing it to inflate.

Preschooler-Friendly Explanation: “Baking soda and vinegar have a special chemical reaction—they make an invisible gas called carbon dioxide. The gas needs space, so it fills up the balloon!”

Light & Color Experiments

7. Rainbow Prism

Materials:

• Glass of water
• White paper
• Sunny day or flashlight

The Wow Factor: Create a rainbow on your wall using just water and light!

Instructions:

1. Fill a glass with water and place it on a table near a window where sunlight comes in.
2. Position the glass so sunlight passes through it and onto a white surface (wall or paper).
3. Adjust the position until you see a rainbow appear!
4. Alternatively, use a flashlight in a darkened room.

The Science: This demonstrates light refraction and the visible light spectrum. Water bends (refracts) light, separating white light into its component colors—just like a prism or raindrops do to create rainbows in the sky.

Preschooler-Friendly Explanation: “White light is actually made up of all the colors mixed together! The water helps break apart the light so we can see all the hidden colors inside.”

8. Color-Changing Flowers

Materials:

• White carnations or daisies
• Food coloring
• Clear vases or cups
• Water
• Scissors

The Wow Factor: Watch flowers drink colored water and change color before your eyes!

Instructions:

1. Fill several cups with water.
2. Add different food coloring to each cup.
3. Trim flower stems at an angle under water.
4. Place one flower in each colored water cup.
5. Observe over 24 hours as the flowers change color!
6. For an extra experiment, split a stem lengthwise and place each half in different colored water.

The Science: This demonstrates capillary action and plant transpiration. The flowers draw water up through their stems to replace water lost through transpiration. The colored water travels up the stem and into the petals, changing their color.

Preschooler-Friendly Explanation: “Flowers drink water through their stems, just like you drink through a straw! The colored water travels all the way up to the petals, changing their color.”

9. Shadow Play Science

Materials:

• Flashlight
• Various objects
• White wall or sheet

The Wow Factor: Create shadow art and learn about light properties!

Instructions:

1. Darken the room.
2. Set up a flashlight pointing at a blank wall or hung sheet.
3. Place objects between the light and wall to create shadows.
4. Experiment with moving objects closer to or further from the light source.
5. Try using translucent or transparent objects to see how light passes through.

The Science: This demonstrates how light travels in straight lines and how opaque objects block light to create shadows. It also shows how shadow size changes based on the object’s distance from the light source.

Preschooler-Friendly Explanation: “Light can’t bend around objects—it can only go through them or be blocked by them. When something blocks the light, it creates a shadow. Moving closer to the light makes your shadow bigger!”

Earth & Nature Experiments

10. Erupting Volcano

Materials:

• Baking soda
• Vinegar
• Dish soap
• Red food coloring
• Small container (film canister or plastic cup)
• Clay or playdough
• Tray or dish (to contain mess)

The Wow Factor: Create a bubbling, fizzing volcanic eruption!

Instructions:

1. Place the small container on the tray.
2. Build a volcano shape around it using clay or playdough.
3. Add 1-2 tablespoons of baking soda to the container.
4. Add a few drops of red food coloring and a squirt of dish soap.
5. When ready to erupt, pour in vinegar and stand back!

The Science: This is the same acid-base reaction as the balloon experiment. The dish soap traps the carbon dioxide gas in bubbles, creating a foamy eruption.

Preschooler-Friendly Explanation: “Real volcanoes erupt when hot lava from deep in the Earth pushes up and out. Our volcano erupts when baking soda and vinegar mix to make a special gas that bubbles up and out!”

11. Growing Crystals

Materials:

• 3 cups water
• 1 cup Epsom salts
• Food coloring (optional)
• Clear jar
• String
• Pencil or stick
• Paper clip or washer

The Wow Factor: Watch beautiful crystals grow overnight!

Instructions:

1. Heat water until very hot (adult supervision required).
2. Stir in Epsom salts until no more will dissolve.
3. Add food coloring if desired.
4. Pour solution into a clear jar.
5. Tie string to a pencil and the other end to a paper clip.
6. Place the pencil across the jar opening with the string hanging down into the solution.
7. Leave undisturbed overnight and observe crystal formation!

The Science: This demonstrates supersaturation and crystallization. The hot water can hold more dissolved salt than cool water. As the solution cools, the excess salt can no longer stay dissolved and forms crystals on the string.

Preschooler-Friendly Explanation: “Hot water can hold lots of invisible salt particles. When the water cools down, the salt particles find each other and stick together, forming beautiful crystals we can see!”

12. Seed Germination Viewer

Materials:

• Clear plastic cup or jar
• Paper towel
• Bean seeds (lima beans work well)
• Water
• Spray bottle

The Wow Factor: Watch seeds sprout and grow roots and leaves before your eyes!

Instructions:

1. Roll a paper towel and place it around the inside of the clear cup.
2. Place 3-4 bean seeds between the paper towel and the cup wall.
3. Spray the paper towel with water untildamp but not soaking.
4. Place in a sunny spot and spray with water daily to keep moist.
5. Observe as seeds germinate over 3-7 days!

The Science: This demonstrates plant germination and growth. Seeds contain stored energy and a plant embryo. When provided with water and the right temperature, they begin the germination process, developing roots and shoots.

Preschooler-Friendly Explanation: “Seeds are like tiny sleeping plants with food packs! When they get water, they wake up and start growing roots to drink more water and leaves to catch sunlight.”

Physics & Motion Experiments

13. Magnetic Maze

Materials:

• Paper plate
• Marker
• Small paper clip
• Strong magnet
• Construction paper
• Tape

The Wow Factor: Move a paper clip through a maze without touching it!

Instructions:

1. Draw a maze on a paper plate.
2. Place the paper clip on the start position.
3. Hold the magnet underneath the plate.
4. Move the magnet to guide the paper clip through the maze!

The Science: This demonstrates magnetic fields and how they can work through other materials. The magnet’s invisible force field passes through the paper plate to attract the metal paper clip.

Preschooler-Friendly Explanation: “Magnets have invisible powers that can reach through things! The paper clip is made of metal, so it’s attracted to the magnet even when the plate is between them.”

14. Ramp Races

Materials:

• Cardboard pieces or foam board
• Books or blocks (to prop up ramps)
• Various small toys with wheels (cars, marbles, etc.)
• Measuring tape
• Stopwatch (optional)

The Wow Factor: Test different ramp heights and surfaces to see what makes things roll fastest!

Instructions:

1. Create ramps by propping cardboard against books or blocks.
2. Set up different heights or cover ramps with different materials (foil, wax paper, fabric).
3. Release cars or marbles from the top of each ramp.
4. Measure how far they travel or time how fast they go.
5. Chart the results!

The Science: This demonstrates gravity, friction, and momentum. Steeper ramps create more acceleration due to gravity, while different surfaces create different amounts of friction, affecting speed.

Preschooler-Friendly Explanation: “Gravity pulls things down the ramp. Steeper ramps make things go faster because gravity pulls harder! Some surfaces are slippery and let things roll really fast, while bumpy surfaces slow things down.”

15. Sink or Float Prediction Chart

Materials:

• Large clear container of water
• Various small objects (cork, marble, crayon, plastic toy, coin, etc.)
• Paper and markers to create a prediction chart

The Wow Factor: Discover surprising results as you test whether objects sink or float!

Instructions:

1. Create a simple chart with object pictures/names and “sink” or “float” columns.
2. Have your preschooler predict whether each object will sink or float.
3. Test each object by placing it in water.
4. Record the actual results and compare with predictions.
5. Discuss why some objects float while others sink.

The Science: This demonstrates density. Objects that are less dense than water float, while objects more dense than water sink. It’s not about size or weight alone, but rather the relationship between an object’s weight and volume.

Preschooler-Friendly Explanation: “Things float when they’re lighter for their size than water. Things sink when they’re heavier for their size than water. It’s like how a huge ship can float even though it’s very heavy!”

Making STEM Learning Stick

These experiments are more than just fun activities—they’re powerful learning opportunities. Here are some tips to maximize the STEM learning potential:

Ask Open-Ended Questions

Instead of explaining everything right away, try asking questions like:

• “What do you think will happen if…?”
• “What do you notice about…?”
• “Why do you think it did that?”
• “What would happen if we changed…?”

These questions encourage critical thinking and help children develop their own hypotheses—just like real scientists!

Document the Process

Create a simple science journal with your preschooler:

• Draw pictures of the experiment setup
• Record predictions
• Note observations
• Compare results with initial guesses

This practice introduces the scientific method in an age-appropriate way. According to Early Childhood Education Journal, children who document their scientific explorations show better recall and understanding of concepts.

Connect to Real-World Examples

Help your child see how each experiment connects to the world around them:

• Link the rainbow prism to actual rainbows after rain
• Connect the tornado bottle to weather events
• Relate the magnetic maze to how a compass works

These connections help children understand that science isn’t just something that happens in experiments—it’s everywhere in their daily lives!

Follow Your Child’s Lead

While these experiments are structured, be open to your child’s questions and ideas. If they want to try a variation or have a different hypothesis, encourage their curiosity! Some of the best learning happens when children take ownership of the exploration process.

Safety First!

While these experiments are designed to be preschooler-friendly, adult supervision is essential. A few safety tips:

• Always supervise experiments, especially those involving water or small objects
• Discuss proper handling of materials before starting
• Have children wash hands before and after experiments
• Store chemicals like vinegar and baking soda out of reach when not in use
• Adapt experiments based on your child’s developmental level

Beyond the Experiments: Building a STEM Mindset

These 15 experiments are just the beginning of your preschooler’s STEM journey. The real goal isn’t just to complete activities but to nurture a STEM mindset—a way of thinking that embraces curiosity, problem-solving, and discovery.

Dr. Elizabeth Rood, Director of the Center for Childhood Creativity, explains: “Early STEM experiences help children develop a growth mindset—the understanding that abilities can be developed through dedication and hard work. This foundation is crucial not just for future STEM learning, but for approaching any challenge with confidence.”

So when your preschooler asks those endless “why” questions or wants to take apart a toy to see how it works, they’re not just being curious—they’re developing their STEM mindset!

Resources for Continued Exploration

Ready to continue the STEM journey with your preschooler? Check out these resources:

• National Association for the Education of Young Children (NAEYC) offers parent resources for early STEM education
• PBS Kids provides free online science games featuring familiar characters
• Boston Children’s Museum Beyond the Chalkboard offers free activity ideas for early childhood educators and parents
• Exploratorium provides science activities for all ages

Final Thoughts

Remember, successful STEM experiences for preschoolers aren’t measured by perfect results or flawless explanations. They’re measured by engagement, excitement, and the spark of curiosity in your child’s eyes.

So when the baking soda volcano makes a mess, or the crystal growing experiment doesn’t turn out exactly as planned, that’s okay! The process of exploration and discovery is what matters most. Each experiment—successful or not—is building your child’s confidence as a scientist, engineer, mathematician, and thinker.

Which experiment will you try first? Share your experiences in the comments below, and let us know what other STEM activities your preschooler enjoys!