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Preschool Lego Science

I just finished a 3 part stay alone series exploring basic science concepts with Legos for 45 minutes with 4 & 5 year olds.  Why Legos? Well, they are very popular from a marketing standpoint, they are plentiful at my library, and easy to clean. I have done a series of Preschool Science classes before so these were the same concepts just with Legos added.

We started each session with a picture of a Lego scientist and we talked about what they do and what body part they do it with.  Any tools that we were using for the program I introduced at this point and modeled what we were going to do with them.

Make Observations
Ask Questions
Use Tools

Week 1: Lego Volcanoes

Legos (could color match if you want for volcano colors)
Duplos  (always good to have depending on fine motor skills)
Baking Soda
Test tubes (but u could use cut water bottles or cups)-Lakeshore Learning Supplies
Plastic trays-Lakeshore

We used the book Volcanoes by Emily Green (c) 2007 as well as a 3 minute video from SciShow Kids.

We also did a short volcano song that I found on Hoopla from Madagascar 2 as a freeze song with scarves. When the music stopped we all had to jump up and erupt.

A few of the boys kept asking me "When are we GONNA BUILD?" So I'd keep the explanation part to 10-15 minutes tops. Plus, you need time to build.

Most kids really wanted to build with actual Legos but actually ended up using Duplos instead because the pieces were larger and less varied.  Each built their structure around the test tube.  One of the students even built a hospital for anyone injured during the volcano eruption. How cute is that?

The test tube contained 2 spoonfuls of baking soda which I let them measure.   Cups filled with vinegar were given to each student and they could use their droppers to add it to the test tube. Here is a short video. The looks on their faces are well worth the clean up.

One great thing about this project was it was a perfect opportunity to clean the Legos. They were disgusting! I just rinsed off the baking soda/vinegar mixture and they were good to go for next week. We left lots of things to dry as the sink was filled to the brim so make sure to have towels handy.

Week 2: Lego States of Matter

Lego minifigures
plastic trays
rubbing alcohol
warm water
Lakeshore trays (or large plates)

This week we talked about solids, liquids, and gasses using What is the World Made Of? by Kathleen Weidner Zoehfeld (c) 1998. Originally I wanted to talk about the Ice Mummy and excavation but I was afraid I'd give the kids nightmares.  The text was very long so I abridged it. My main vocab was matter, solid, liquid, and observation for the day.
Our hands on project was melting a Lego mini-figure from solid to liquid. I froze salad sized plastic bowls with water and Lego men. You have fill it half way freeze it, then fill it the rest of the way since the Lego men float. I placed some materials to test: salt, warm water, alcohol, sugar and we observed which table made their ice melt the fastest. We started with salt on one table, sugar on the other with little to no results. Then I gave one table warm water and another rubbing alcohol. Water was the definite winner. 

I saw an online post about using rubbing alcohol, dish detergent and water in a mix to defrost your windshield so we added rubbing alcohol as a last minute independent variable. Out of all the variables the kids concluded that warm water worked the best, followed by rubbing alcohol. We had plenty of time to independently build after this project so it could be easily done in a 30 minute time frame. 

Week 3: Lego Gravity

Legos and minifigures
Various things to drop

This week inspired by I Fall Down by Vicki Cobb, we talked about gravity and how it keeps us on the ground. The kids giggled when we talked about floating in the air without gravity and how would we run? sleep? get dressed? We weighed different objects with our Lakeshore scales and made predictions which one would fall first. Besides the feather (which had to do with wind resistance) all the items fell at the same time. Make sure to drop all the objects yourself. Having kids help might have changed the timing of the drop and skewed the results.
After the short 5-10 minute guessing game and intro, we started building items that we could race down the ramp or take to the zip-line. I think it might have been better to talk about Forces & Motion rather than Gravity since there were so many factors to a successful zip-line trip like the angle of my arm on the ladder, what material I used, how much each weighed, where I put the paperclip, etc. So although gravity sent them all to the ground, there were too many other factors to have a center focused question like does it matter how much the Lego construction weighed? Be prepared that kids might not want to destroy their creations on the zip-line or ramp.

What I tried to accomplish most out of these classes was to use the vocabulary of a scientist and modeling asking lots of questions and making predictions. You can pander to kids love of experimenting, natural curiosity, and Legos. Out of all the projects we did every time without fail the kids would ask if we were going to do volcanoes again. If I could keep one activity, I think that one would be the winner.


  1. Great activity. I'm definitely keeping this one in mind for future reference.


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