Oobleck

Begin your class by reading Bartholomew and the Oobleck by Dr. Seuss.

Then have your students make their own Oobleck:
--Mix 3 spoonfuls of cornstarch with 2 spoonfuls of water. 

Next comes play time...
Students stick their hands in the Oobleck to see what it feels like and how it behaves.  They should try some of these other tests as well, recording their results after each one:
--Poke it quickly
--Poke it slowly
--Stir it fast
--Stir it slowly
--Pour it
--Roll it into a ball
--Set objects on it

Now students need to decide if the Oobleck is a solid or a liquid.  Make them defend their decision in a written statement.  Perhaps you'll even get a debate going between students. 

You've actually created a suspension that acts as both a solid and a liquid.

**Do NOT try to get rid of your Oobleck by putting it down the drain - just put it in the trash.  Or better yet, allow the water the evaporate and put the dried cornstarch in a plastic bag for your next batch of Oobleck.