The first law of thermodynamics states: energy can be neither created nor destroyed (conservation of energy). Zippy's science book does a nice job of explaining this with a play doh example. Using 4 cans of play doh make a world, then you can change it around, but one is still using the same play doh.
After she was done reading about this Zippy asked if she could try it. So she did. I think she will remember the conservation of energy after this. That is why I love homeschooling.
Here is her play doh creation: