Erupting Soap Experiment

Science can be simple because the best experiments I’ve done with my kids use items we already have at home. This Erupting Soap Experiment is one of those exciting activities that only takes minutes to prepare but leaves a big impact.

If you’re looking for more fun ideas like this, check out my page on easy experiments here: Simple Homeschool Science Experiments. It’s full of hands-on, kid-friendly science ideas that are easy to try at home.

Stick around because I’m walking you through a fast and fascinating experiment perfect for curious minds in early elementary. You’ll only need two supplies, and the results are super satisfying. You will also learn how it works and what your kids will take from the experience.

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Three Interesting Facts About Soaps

Soap has been around for thousands of years, and it’s more than just a way to stay clean.

• Soap contains air pockets that make it float, especially in the case of Ivory soap.
• Soap molecules have two sides: one attracts water, the other repels it. This is how soap lifts dirt and oil from skin.
• Some soaps expand when heated due to trapped air and moisture. That’s what makes this activity so much fun.

Recommended Science Experiment Books

If your kids love science time as much as mine, keeping a few experiment books on hand is a game-changer. They’re packed with ideas that make learning science exciting and approachable.

Awesome Science Experiments for Kids: 100+ Fun STEM / STEAM Projects and Why They Work (Awesome STEAM Activities for Kids)The Everything Kids’ Science Experiments Book: Boil Ice, Float Water, Measure Gravity-Challenge the World Around You!Awesome Kitchen Science Experiments for Kids: 50 STEAM Projects You Can Eat! (Awesome STEAM Activities for Kids)Awesome Outdoor Science Experiments for Kids: 50+ STEAM Projects and Why They Work (Awesome STEAM Activities for Kids)Steve Spangler’s Super-Cool Science Experiments for Kids: 50 mind-blowing STEM projects you can do at homeSmithsonian 10-Minute Science Experiments: 50+ quick, easy and awesome projects for kids

 

The Science Behind This Soap Experiment

This activity works best with Ivory soap because of how it’s made. Ivory soap has tiny air pockets whipped into it during production. When it heats up in the microwave, the water inside turns to steam, and those air pockets expand rapidly.

The result is a puffed-up, foamy cloud that looks nothing like the bar you started with. It’s not just neat to watch—it’s a real example of physical change, and once it cools, it’s safe to touch. We’ve done this more than once, and my kids are always surprised by how big the soap grows.

Recommended Science Printable Packs

My science printable packs are a go-to for quick, ready-to-use learning tools. They help reinforce what we explore during experiments and extend the learning.

What Can Kids Learn From This Experiment?

This simple activity allows kids to explore fundamental scientific concepts in a way that feels like play.

• Understanding physical changes and properties of materials
• Observing cause and effect in a safe environment
• Using scientific thinking and asking questions

Recommended STEM Kits for Kids

If your kids enjoy hands-on learning, STEM kits are a fun way to explore different science and engineering topics. They come with all the essentials to keep kids curious and engaged.

110 Lab Experiments Science Kits for Kids – STEM Projects Educational Scientific Toys for kids 6 7 8 9 10 12 Years Old, Christmas Birthday Gifts for Boys and Girls, Chemistry Set, Learning & EducationNational Geographic Kids Junior Chemistry Set – Complete Early Learning Lab Kit with 50 Science Experiments and 20+ Lab Tools for Kids Aged 4-6Science Magnets Experiment Set for Kids Electricity and Magnetism Kit for Students Stem Kit Physics Lab Basic Circuit Tools for Learning StarterJapace 100+ Experiments Science Kit for Kids, Cool Boy Christmas Birthday Gift Ideas, Chemistry and Physics Set STEM Toys for Boys GirlsDoctor Jupiter My First Science Kit for Kids Ages 4-5-6-7-8-9-10-11-12 | Birthday, Easter Gift Ideas for 4+ Year Old Boys & Girls | STEM Learning & Educational Toys | Preschool Learning ActivitiesScientific Explorer My First Mind Blowing Science Experiment Kit, 11 Mind Blowing Science Activities and Experiments (Ages 6+)

 

Ivory Soap Science Activity Supplies

• Ivory soap (other brands won’t give the same result)
• Microwave-safe plate
• Microwave

Making the Erupting Soap Experiment

We’ve done this experiment several times over the years. My daughter especially loved watching the soap puff up the first time we tried it. It was one of those moments where she couldn’t stop talking about it all afternoon.

What I appreciate most is how quick the prep is. We always have Ivory soap around, and grabbing a plate and popping it in the microwave is about as simple as it gets.

Even my older kids got a kick out of it the first time. They started asking questions about the steam and expansion, which became a great conversation about matter and how heat affects different materials.

More Science Experiments to Try

Science can be fun and straightforward when you find the right activities. Here are more experiments we enjoy:

• Lemon Volcanoes Experiment
• How to Grow a Crystal
• Elephant Toothpaste Experiment
• Magic Milk Experiment
• Balloon Air Pressure Experiment by Darcy and Brian
• Skittles Science Project by Homeschool Preschool

I love finding ways to make science feel approachable for my kids, and this puffy soap science activity is always a hit. It doesn’t require fancy tools or supplies and is quick enough to do on a busy afternoon. I hope it also brings some learning (and a few smiles) to your day.