Insta-Snow is a super absorbent polymer. Let kids watch as It is made so they can see the powder absorb the water. You could also use it with measuring cups and containers of different sizes, or with small plastic polar animals.
Preschool art show: bubble prints ( I mixed 2 table spoons of paint with dish soap and water. Let the kids use a straw to blow bubbles, then press paper onto the top of the cups to make the bubble prints!