Old bar of soap

Magical expanding soap

Ivory soap differs from most other brands in that it floats in the water. The reason – there is air whipped into the soap which makes it lighter than water. The small air pockets in the soap make for a very interesting effect when the soap bar is heated up.

  1. Take a bar of ivory soap and place it on a paper towel
  2. Place the bar in the microwave and microwave for 2 minutes
  3. If your microwave has a window, watch the soap bar as it microwaves.
  4. Allow the bar to cool for 1 minute before taking it out of the microwave

Weird huh? The bar of soap will expand into a huge, billowy, puffy mass of white stuff – looks like clouds! The effect you see is similar to the effect popcorn produces when it is cooked. Soap contains water molecules and in the case of Ivory soap, which has air pockets whipped into it, when the water turns to vapor during heating, the vapor is trapped in these little air pockets. This causes the soap, which becomes soft and pliable when heated up, to expand.

Jacques Charles – creator of Charles’ Law. Given Charles’s unkempt look in this photo, Reeko can only surmise that it is a drivers license picture (or given the glazed look in his eyes, possibly a mug shot).This is a demonstration of Charles’ Law (named after the guy with the glassy looking eyes pictured here) which states that as the temperature of a gas increases, so does its volume. When heated, the water molecules begin moving very fast and away from each other and hence, the expanding soap effect we see in this experiment.  Jacques Charles was an avid balloonist and in addition to developing several hot air balloon parts that are still used today, he developed this law in order to improve the performance of the balloons that he created and flew.

Interesting fact

For more than 75 years, Ivory’s most famous feature – its ability to float – grew to legendary proportions.  But Ivory’s unique characteristic was actually the result of a mistake! The story begins with an employee who forgot to shut off the soap-making machine when he went to lunch. He returned to find the soap mixture puffed-up and frothy. However, because the longer mixing time had not changed the ingredients in any way, the soap was finished and shipped as usual.

About a month later, when P&G started receiving requests for more of the “floating soap,” the accident was discovered. The forgotten lunch-time mistake had produced a unique floating soap!

Experiment Supplies

Supplies: Soap


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