The day started with the grinding of chalk into water and the question: "How much chalk would I need to make this mixture solid?"
Which reminded me of Goop.
Ah goop. Noor was first introduced to this marvelous substance a few years ago by the parents' of her now best friend. I believe they made a tub of it that was large enough to stand in. We didn't go that large-scale, but Noor went through two boxes of cornstarch in a flash.
1 Cup cornstarch
1/2 water with a few drops of food coloring--add slowly to the cornstarch and stir.
We talked about states of matter, atoms and molecules and about how cornstarch, which is made of loooong chains of molecules is a polymer. Goop acts like a solid when it is pressed together in your palm because the molecules are really close together--the chains get entangled. If you relax your grip on the goop, it flows like a liquid because the chains of molecules have space to move around each other.
Noor added more and less water to subsequent batches, made some inside a plastic bottle and experimented with how shaking and pouring effected the suspension.
It was clear she was working through a deeper understanding of the states of matter when later that evening, she told me that ghost are a gas. "Why," I asked. "Because their molecules are really far apart, which is why they can pass through walls."