Balloon Rockets - I've done this in several science camps I've conducted. Kids have fun with it. But, when the balloon deflates it may fall off the straw because it's surface area changes - another good thing to show and explain to kids.
Another pinner says: How Many Drops of Water Can a Penny Hold? My daughter did this as her science fair project last year and it was very popular. She even used water variations (Kool-aid, salt water, etc).
Elephant Toothpaste - cup hydrogen peroxide liquid is a solution, which can be found at a beauty supply store or hair salon), 1 Tbs (one packet) of dry yeast, 3 Tbs of warm water, liquid dish washing soap and food coloring
BENTLEY INVESTIGATIONS---A hands on fire safety lesson which incorporates life skills, sequencing and fine motor skills. Perfect activity for the special education classroom. My students have autism and other disabilities and they loved it!