Learn the chemistry behind the reaction between calcium carbide and water...melon...?!
This Pumpkinator is a fantastic orange-to-blue-to-orange chemical reaction that will make a great addition to your Halloween-themed chemistry demonstrations.
The Devil's Milkshake is a simple, yet interesting chemistry experiment that fits well as a Halloween demo.
You can perform an orange to black chemistry demonstration using materials commonly found in stores. The reaction appears to be similar to the Old Nassau reaction, but uses greener reagents. This is a great demonstration to do around Halloween time.