While investigating the different states of matter, I threw a curve ball - Ooblek.
Ooblek is made from cornstarch and water, and when it's mixed to the right consistency it exhibits strange behavior. It's considered a Non-Newtonian substance because it doesn't obey the regular laws of viscosity. You can pour it, and you can sort of stir it- but if you apply pressure it hardens. My favorite stunt is to slap the substance. Everyone (including myself) shirks, waiting for it to splash all over the place, but it hardens upon impact.
After playing and exploring with the Ooblek, the Magical Minds were asked to reflect on the material. Is it a liquid or a solid? They used the following indicators to formulate their thinking.