Sunday Science – Soap Expansion

I like science and I really like seeing what happens when matter changes state – especially if it involves heating stuff or setting fire to it – so when I read about putting soap in a microwave I knew I had to try it!  The blog I read was at 5 Orange Potatoes and used Ivory soap.

It turns out that the kind of soap you use is important – but that’s OK because science is all about experimenting!

Here’s what happened to my little bar of soap  …


The idea was to put the soap in the microwave and see what happened as it heated up.  I knew it wouldn’t just melt like in a saucepan because microwaves heat the particles differently.  I put the microwave on for a few seconds and soon smelt a kind of burning soap and plastic smell.  So I opened the door to see what was going on.

SOAP FACT #1 It got so hot that it melted the plastic container …


I moved the soap (carefully) to a pyrex dish and tried again.  The plastic burning smell went away but the soap smell definitely stuck around!  Here’s how the soap ended up …


SOAP FACT #2 The water molecules in the soap get energy from the microwaves and move faster and further apart.  This makes the air inside the soap expand and it goes all foamy. My soap didn’t have a high air content so it didn’t foam very much.

It wasn’t quite as exciting as the blog I read but it was still cool.  I’m going to try the Ivory soap next 😀


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