We are not the only family who believes that summer should be a season of STEM activities for kids. In fact, many families do STEM and science activities in the summer (check out my science summer camp if you need some new ideas). Still, although we have tried hundreds of science experiments for kids, we had yet to try the classic Ivory soap science experiment.
How? I don’t know, but if you are looking for the easiest science experiment ever, definitely try the Ivory soap science experiment. This soap experiment would be perfect for a rainy day!
The Classic Expanding Soap Science Fair Project
Use this soap experiment as a jumping off point for more soap science experiments, like the soap-powered boat science project!
In the classic expanding soap science experiment, kids can learn how air can expand certain objects making them filled with air, but not changing their chemical structure or density in any way.
Microwave Ivory Soap Science Experiment Explanation
Ivory soap expands in the microwave due to it’s formulation.
Ivory soap is designed with a lot of air inside it, because the manufacturers wanted the soap to be able to float in the bath tub, rather than sinking to the bottom.
When you put the soap in the microwave, a chemical reaction happens.
When the air gets hot, the air pockets expand with moist air, forcing the bar of soap to inflate and puff up.
If you like, try microwaving other kinds of soap to see what happens. Do all soap bars expand? Do some shrink or melt?
Which soap has the biggest reaction?
Supplies for the Ivory Soap Experiment
How to Do the Ivory Soap Experiment
This project is so, so simple. First, ask kids what they think will happen to the soap as a hypothesis. It’s common for them to expect it to melt or burn. If kids have done the experiment before, don’t let them give it away to the other kids!
Heat the Ivory soap in the microwave to see what would happen.
It took about two minutes before the soap stopped expanding. I bought our soap a while ago, so I don’t know if it would have expanded even further if it was new (which could be another science experiment!).
We heated our soap several times to see if it would keep expanding, but it stopped after a minute or so, probably because all the moisture dried up.
Next, try heating other brands of soap and compare the results with the Ivory soap results.
For some reason, I thought the soap would feel soft and squishy after heating, but it didn’t. It was hot, but still hard.
The type of microwave and its intensity will change how much your soap bar exands. If you have a lower watt microwave, the soap will expand less. Some microwaves will expand the soap into a huge puffy cloud, while others will cause the soap to remain somewhat small and only minorly inflated.