Sunday, October 31, 2010

Goop: Is it a solid or a liquid? It is a suspension!

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."


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