What is an oil spill, Mommy?

One of my jobs as mom is to try to explain the world in language that a 4-yr-old can understand. When I got the question, "What is an oil spill?", I tried an explanation of drilling, pumping, leaky pipes, and environmental catastrophe, but eventually had to go with a demonstration.

We started with a bowl of clean water:

Added a few drops of sesame oil (it was the darkest oil I had, and also the smelliest):
Swirled the oil around a little, and found out that even though there wasn't very much of it, it stuck to our fingers when we put them in the water:

Then we tried to clean the water. We added Dawn detergent, and it certainly moved the surface oil out of the center, but there was really no place for it to go:

Finally, we stirred the detergent in, and ended up with an evenly dispersed, foamy mess:

I don't know how much of this Blue and Pink understood, but they got that adding oil to the water meant that 1) we didn't want to drink that water or swim in it and 2) we had a hard time getting it cleaned up. My heart aches to think about the disaster in the gulf right now, and I hope that somehow the health of that area will someday be restored.