What you’ll learn: This activity is a great way to teach your child about the behaviour and properties of a gas when heated.
What you’ll need:
- A bar of ivory soap (must be ivory)
- A microwave safe plate
- When the soap appears to stop expanding, stop the microwave and remove it.
- A microwave
What to do:
- Put the bar of soap (unwrapped) on the plate and put it in the microwave
- Heat it for 2 minutes
- Watch the magic happen!
- Do not touch the soap for at least 2 minutes (or until cool)
After you’ve witnessed the experiment:
- Discuss what happened to the soap. Why did it expand?
- Explain that the microwaves excited air molecules inside the soap, which caused them to vaporize.The vaporization of these molecules caused tiny air pockets to rapidly expand. Given that the soap molecules were heated (and therefore soft), the expanding air and water molecules were able to push the soap out in a foam-like substance.
- Ask the question: is the soap chemically different than it was before? Explain that there was no chemical reaction during the experiment, only a physical one, so the substance of the soap remains the same.
- Finally, explain that this experiment is a demonstration of Charles’ Law, which states that the volume of gas increases with temperature.
