Where'd The Water Go?

This week we conducted a science experiment.  I had to cups, one labeled A and one labeled B.  I showed the students that both cups were empty and I then poured water into both cups.  I asked for an assistant to come up front and I then poured one of the cups of water over her head.  BUT...no water came out of cup A.  Where did the water go???  

I posed a question to the students and they then formed their hypothesis as to what they thought happened to the water.  The most common hypothesis I received was that there was a paper towel in the bottom of the cup.

 Once we discussed a few of the students hypotheses I then passed the cup around.  They saw that inside was a diaper that has a substance that soaks up liquid.  The substance inside turns into gel-like crystals when it gets wet.  They were so intrigued by this!