Check out our new astronomy
project...
Click here to find
out more
Let's get artistic...
What you need:
- Bar of soap - make sure it's one that floats in water. Ivory
Soap is famous for floating
- Microwave
- Bowl or kitchen roll
How to:
Make sure you ask an adult for help with the microwave.
- Place the bar of soap on a piece of kitchen towl or in a bowl
and put it in the centre of the microwave.
- Cook the bar of soap on high for two minutes. Keep watching it!
The bar of soap will expand into puffy clouds. Make sure you don't
overcook it.
- Allow the soap to cool for at least one minute before you touch
it.
The bar of soap should look puffy, but it should still feel the
same as it did before you put it in the microwave. You can still
take it in the bath!
What's happening?
Soap that floats on water has air pumped into it during the
manufacturing process. This makes it less dense
than water, so the soap floats. Air bubbles in the soap contain
water. Microwaving the soap causes the water to heat up. The heat
causes the air bubbles to expand and makes the soap sculpture grow.
This is Charles' Law. Charles said that as the
temperature of a gas increases, so does its volume.
If you use a bar of soap that doesn't float on water, it won't
have as many air bubbles in it. These bars of soap will heat up and
melt in the microwave! Very messy.
Charles' Law explains what happens when you put a marshmallow or
popcorn kernels in the microwave - they expand. Try it and see!