Looking for a quick and amazing science experiment to try with kids? This Ivory soap experiment is a must-do! Watch what happens when you microwave a bar of soap—it’s fun, fast, and full of science. This simple activity explores physical changes and states of matter using a common household item.
Ivory Soap in the Microwave
- Field of Science: Physical Science
- Grade Level: Preschool to Grade 5
- Concepts Explored: Physical change, states of matter, gas expansion
When Ivory soap is microwaved, it goes through a physical change. The bar puffs up dramatically due to trapped air and moisture inside. As the air heats, it expands, causing the soap to form a foamy, cloud-like structure. No new substance is formed, and the soap is still usable afterward, making this a great example of a reversible change.
Supplies Needed
- 1 bar of Ivory soap (other brands won’t work the same!)
- Microwave-safe plate or bowl
- Microwave
- Optional: tray and accessories for sensory play
- Printable science sheets below
How to Microwave Ivory Soap
STEP 1:
Unwrap the Ivory soap and place it on a microwave-safe plate or bowl.
STEP 2:
Microwave the soap on high for 1 to 2 minutes. Start with 1 minute and observe. The soap will puff up into a big, foamy cloud!
STEP 3:
Let the soap cool before handling. Once it’s safe to touch, explore the texture and shape. You can even break it apart for sensory fun!
Why Does Ivory Soap Expand in the Microwave?
Ivory soap is filled with tiny air pockets from the manufacturing process. When heated, the water molecules and air inside the soap expand. The softened soap structure stretches with the rising pressure, forming the iconic soap “cloud.”
This process is similar to how microwave popcorn pops—both rely on the expansion of gas trapped in the material.
Ivory Soap Science Information
There are two main types of change:
- Reversible change: A change that can be undone, like melting ice or expanding soap.
- Irreversible (chemical) change: A change that cannot return to its original form, like baking a cake or cooking an egg.
This Ivory soap activity is a reversible change. The soap expands but remains soap. It hasn’t changed chemically—it’s just changed shape and texture.
👉 Want more examples?
- Melting chocolate (experiment) = reversible
- Baking Bread (experiment) = irreversible
Suggested NGSS Connections by Grade:
Kindergarten (K-PS1-1):
Use observations to describe how heating or cooling a material causes changes that can be observed.
1st Grade (1-PS4-1, crosscutting concept):
Use light/heat to cause observable changes in matter.
2nd Grade (2-PS1-4):
Construct an argument with evidence that some changes caused by heating or cooling can be reversed and some cannot.
Extension Activities
- Mold the puffed soap into shapes for a soap sculpture.
- Add coloring and water to re-form the soap into custom shapes.
- Compare different brands of soap to see if they react the same way. (Spoiler: they don’t!)
Ideas to Extend for 3–5th Grade:
- Compare brands of soap to test which ones expand and why.
- Measure volume before and after to calculate the change.
- Discuss particle behavior and gas expansion using diagrams.
- Introduce reversible (physical), irreversible (chemical), and phase change.
Make It a Science Project
- Question: What will happen when I microwave Ivory soap?
- Hypothesis: I think the soap will melt or change shape.
- Experiment: Microwave the soap and observe.
- Observation: The soap puffs up and forms a foam-like cloud.
- Conclusion: The heat caused the air and moisture in the soap to expand, changing the soap’s appearance.
🔎 This is a great opportunity to explore the scientific method, learn how to write a hypothesis, and choose variables!
Related Science Activities
- Melting Crayons Experiment
- Solid, Liquid, Gas Science Activity
- Make Butter in a Jar
- Ice Cream in a Bag
- Starburst Candy Slime
- Popcorn Experiment
- Melting Chocolate Experiment
Grab the Free Printable Ivory Soap Activity
Want to save this experiment for later or add it to your science journal? Download the Ivory Soap Printable Project Page to record supplies, steps, and your observations!
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I couldn’t find the recipe for clean mud/ How much toilet paper ,how much water and how much ivory soap?
Hi this is not a clean mud activity which is probably why you can’t find it. This is a really cool experiment using just a bar of ivory soap! Here’s a friends clean mud or ghost mud recipe you can check out, http://happyhooligans.ca/ghost-mud-ice-cream/
Does it need to be ivory soap, or can I just use regular soap?
Ivory Soap is the preferred soap for this experiment.