Why is it that when a bar soap is new, it foams real good but as it gets smaller, it foams less?

Question

I think it should foam the same because it’s the same contents that are still in it.

In: Chemistry

Answer 1

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Answer 2

>I think it should foam the same because it’s the same contents that are still in it.

Does it? Soap starts out as a dry bar. As you use it, water soaks in and air gets displaced and diffuses out.

However, it is probably due to the surface area of the new and used bar. Because the used bar is smaller, it releases less soap molecules over the same period of time. In other words, in order to get the same amount of foam, you’re going to have to work the bar longer.