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Can You Power a Boat with Soap? STEAM Challenge

Can you power a boat with soap? Check out this fun surface tension STEAM challenge and make a soap powered boat!

We love a good STEAM Challenge Saturday! This week, we set out to make some soap powered boats! It’s already in the 40s here in Wisconsin, so we did our activity inside because we didn’t want to brave the cold with our water.

BH FB Surface Tension STEAM Activity

We’ve worked with density and surface tension with simple pepper and soap in water demonstrations, so we decided to up the ante and see how we can control the surface tension of the water by adding just enough surfactant to make our boat move.

Then, we looked at our raft design and used our engineering skills to come up with more effective designs for our surface tension driven raft!

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Why STEAM Activities?

STEAM is the abbreviation for Science, Technology, Engineering, Art, and Math.

For the month of October, we will be sharing a daily low-prep STEAM (Science, Technology, Engineering, Art, Math) activity. You and your kiddos are going to love all of the low-prep STEAM activities that we have in store at OurFamilyCode! #daysofSTEAM #31dayschallenge #STEAMactivitiesforkids #monthofSTEAM #scienceforkids #engineeringforkids #technologyforkids #artforkids #mathforkids #lowprepSTEAM #5minuteSTEAM #STEAM #STEM

STEAM, like STEM, is an integrated approach to learning that encourages learners to make connections between the concepts they are learning and how they apply them to real-world problems.

STEAM helps students ask questions, problem solve, think creatively, and produce innovative solutions. Many schools have adopted STEAM learning activities into their curriculum, but it’s never too early to start building critical thinking skills.

We love to learn through play at our house and have a blast doing activities for toddlers all the way to tweens!

STEAM Kids Pin

Looking for some more hands-on activities that incorporate Science, Technology, Engineering, Art, and Math (STEAM)? Then you have to check out STEAM Kids! 

This book features more than 50 hands-on activities that are organized into easy to implement categories, so you know exactly what concepts your kids are learning! 

Grab your copy from Amazon today or get instant access to this great book by purchasing a downloadable PDF!

Key Surface Tension Activity Terms

  • Surfactant – a substance that has the ability to reduce the surface tension of a liquid
  • Length- the measure of how long an object is
  • Fluid – any substance made up of particles that flow or move freely
  • Surface tension – property of liquids that describes the attraction of liquid particles at the surface

Soap Powered Boat Surface Tension Challenge Materials

Can You Power a Boat with Soap? STEAM Challenge

Cut styrofoam into a small rectangular shape. This will be the raft.

Cut a small square (about 1-inch by 1-inch) from the center of one end of your raft. This is the back of the raft.

surface tension raft materials

Cut a 1-inch by 1-inch square from your sponge. This sponge piece should fit into the square on the back of your raft.

Push a toothpick through your sponge and rest it on the edges of your raft. This will hold your sponge in place. Make sure the bottom of your sponge is at least even with the bottom of your raft and touching the water.

surface tension toothpick sponge 2
surface tension sponge raft 2

Cut a toothpick slightly longer than 1-inch and push the ends of the toothpick into the styrofoam ends behind your sponge. This will keep your sponge in place.

surface tension soap boat toothpick sponge

Fill your bucket or sink with water and let it settle. Place your raft in the water. Make sure it has enough room to move forward.

raft water

Add 1-2 drops of dish soap onto your sponge. Make sure to put the soap on the sponge and not the water. You can use a medicine dropper to place your drops carefully.

surface tension sponge soap before

Watch your raft move! Grab a ruler and measure from the starting point of the sponge to the ending point of the sponge!

moving raft surface tension
STEAM word design

Connect this Soap Powered Boat Experiment with other STEAM Buckets

Check out these STEAM extensions!


Try different substances other than detergent such as vegetable oil, salt, toothpaste, or rubbing alcohol. Observe what happens. Did the other substances affect the surface tension and the motion of your raft?


Watch out this video of a robotic water strider from Harvard University. A water strider is an insect that walks on the surface of water. Check out the surface tension under the feet of the water strider! As it walks, the water is depressed underneath the water strider’s feet.


Change the shape of your raft and do the experiment again. Does the raft move further when it’s smaller?


Blow some bubbles and make bubble art! Bubbles are a great example of surface tension.


Measure how far your raft moves with each substance. Compare your results to one another.

Some Books to Read with this Soap Boat Activity

We love incorporating books into our activities. Here are some great books about water to read with your activity!

31 Days of STEAM Activities AD

31 Days of Low-Prep STEAM Activities for Kids

This activity is part of our 31 Days of Low-Prep STEAM Activities for Kids. Every activity focuses on each of the buckets of STEAM (Science, Technology, Engineering, Art, & Math) although these integrated projects fit in more than one bucket.

You and your kiddos are going to love all of the activities that we have in store! Visit the 31 Days of Low-Prep STEAM Activity hub and pin it, so you can come back and visit it daily!


Can you move a raft with soap? Check out this fun surface tension activity! #STEAMactivities #STEM #STEAM #scienceforkids #kidactivities #teachingkids #elementaryscience

Meet Toni, the Maker Mom behind Our Family Code

A picture of Toni, the author, wearing a green tie dyed shirt.

Hey there, I’m Toni! I’m a software engineer and Maker Mom that finds my joy in unleashing my children’s curiosity by exploring STEAM concepts with my fantastic five!

When I’m not chasing toddlers or raising tweens, you can find me tearing things up and putting them back together over here at Our Family Code.

I am the owner and content creator of multiple educational websites designed to increase access to STEAM & STEM education with a focus on teaching computer science and coding to kids of all ages!

You can also find out more about me by visiting!

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