Growing Ivory Soap Science Experiment

Science experiments are always fun, hands-on ways for young children to learn.  In this Growing Ivory Soap Science Experiment, students will watch as a simple bar of soap expands as it is cooked.  This simple science experiment for kids is sure to be one of your students’ favorite lessons of the year.

The Ivory Soap Science Experiment:


  • Bar of Ivory Soap (only Ivory soap will work!)
  • Paper Plate
  • Microwave
  • Sensory Bin (or plastic container)


1. Put the bar of Ivory soap on the paper plate inside of the microwave.

2. Microwave for one minute.

3. Watch the soap as it begins to expand.  (You can open up the door of the microwave to show your students how the bar of soap is changing)

4. Allow the soap to cool for a minute or so before touching it.

5. Place the puffy soap into a sensory bin and let your students touch and explore it.


For this Growing Ivory Soap Science Experiment, I have my students work with a partner and microwave one bar of soap for each pair.  The soap is brittle and will begin to crumble as your students touch it, so each child will have a chance to explore it when they work with only one other child.

The Science Behind The Experiment:

The Ivory soap expands because it is full of little air pockets.  If you hold a bar of Ivory soap and another brand of soap in your hands, you can feel how much lighter the Ivory soap is in comparison.  The air pockets are the reason why a bar of Ivory soap is the only kind that will float.  (which is another fun experiment!) As the Ivory soap softens in the microwave, the water molecules inside of the air pockets heat up and cause it to expand.


Extend The Learning:

  • Have students make predictions about what will happen to the the bar of soap prior to beginning the experiment and draw conclusions after cooking the soap.
  • Microwave another brand of soap and compare the results.
  • Measure the weight and height of the Ivory soap before and after it is cooked.

Make Your Own Bar Of Soap:

After your students have explored the puffy soap, have your students turn the crumbled, cooked soap into a new shape.  Since Valentine’s Day is just around the corner, we made heart-shaped bars of soap.


  • 2 Tablespoons of Warm Water
  • Cookie Cutters
  • Wax Paper
  • Food Coloring (optional)


1. Add 2 tablespoons of warm water to each crumbled bar of soap.

2. Mix the water and soap together until it has a consistency like play dough.

3. Add food coloring and mix it together.  (optional)

Since we wanted to make hearts, we added 3 drops of red food coloring and mixed it together till it was well blended.

4. Place a cookie cutter on top of a piece of wax paper and fill the cookie cutter with the soap mixture.

5. Let the soap air dry till it becomes hard.

6. Place the soap into a plastic bag or treat bag for the students to take home.


One bar of Ivory soap makes about two heart-shaped soaps that are about three-inches wide.

Your students will not only have fun watching a bar of soap expand as it is cooked in this Growing Ivory Soap Science Experiment, but they will also love transforming this sensory activity into their own bar of soap to take home too.

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