[nikkie]

Originally Posted by happy_terd

thanks. This is difficult getting her to understand. So far the best kid friendly definition I found was:

"It is, essentially, a measuremement of how tightly matter is crammed together."
http://physics.about.com/od/fluidmec.../f/density.htm

Yeah, I think the real problem is that you have to have a good solid understanding of mass before you can really grok density. And understanding mass means taking it back to atomic mass and the periodic table. And that would take a while.