STEM Activities for Preschoolers: 10 Simple Science and Engineering Experiments

Science thinking isn’t a school subject for preschoolers — it’s a habit of mind. Children who ask “what happens if?”, make predictions, test them, and observe results are building the reasoning skills that show up in every academic domain. These 10 activities cultivate that habit through genuine, hands-on inquiry.

The Preschool Science Method

The scientific method for 3–5-year-olds has 4 steps:

1. Wonder: What do you notice? What do you wonder?
2. Predict: What do you think will happen?
3. Try: Do the experiment. Observe carefully.
4. Talk about it: What happened? Was your prediction right?

Run every STEM activity through these four steps. The habit of predicting before observing is the most important STEM practice you can build.

10 Preschool STEM Activities

1. Sink or float? Collect 10 household objects. Predict: sink or float? Test in a bowl of water. Record results. Discuss: what do the floaters have in common? What about the sinkers? This is density and material properties at the preschool level.

2. Baking soda and vinegar. The classic. But make it scientific: predict what will happen. Add different amounts of vinegar. Add food coloring and watch it mix. Why does it bubble? Introduce the word “reaction.”

3. Ice melting investigation. Put ice in 3 containers: one in the sun, one in shade, one wrapped in a towel. Predict: which melts first? Check every 10 minutes. Graph the results. Heat transfer and insulation for preschoolers.

4. Bridge building challenge. Using blocks, cards, or popsicle sticks, build a bridge that holds as many pennies as possible. Test. Rebuild if it collapses. This is engineering process: design, build, test, redesign.

5. Magnet exploration. Which objects are magnetic? Test a set of household items (paper clips, coins, buttons, rubber bands, pennies). Sort by magnetic/not magnetic. Discuss: what do the magnetic objects have in common?

6. Seed observation. Plant a seed in a clear cup so roots are visible. Observe daily. Draw what you see. When does the first root appear? The first shoot? This builds systematic observation and biological concepts.

7. Light and shadow investigation. Use a flashlight in a darkened room. How does shadow size change as the light moves closer? Make shadow puppets and observe what changes shape. Light and optics are accessible to preschoolers through shadow play.

8. Ramp and roll. Build a ramp from a board and some books. Roll different objects: ball, car, cube, cylinder. Predict: which goes farther? Test. Does the ramp height change the result? Physics of slopes and rolling.

9. Mixing colors. Red + yellow = ? Blue + red = ? Yellow + blue = ? Document each mixing. Extend: can you make orange? Brown? The unexpected outcomes (yellow + blue = green!) naturally elicit wonder and prediction.

10. Paper airplane design. Build three different paper airplane designs. Predict which will fly farthest. Test. Measure with steps. Try modifying one design. Data collection and iterative design process for 5-year-olds.

The STEM Language That Matters

The vocabulary of STEM — observe, predict, experiment, hypothesis, evidence, result, conclusion — is academic language that appears in elementary school science assessments. Introducing these words in preschool STEM activities builds the vocabulary foundation for formal science instruction. Use the words naturally: “What’s your hypothesis? Let’s test it. What did you observe?” The concepts behind the words will be familiar when they appear in a textbook.