A way to demonstrate how the particles move in matter is to get some packing peanuts and put them into a 2 liter bottle.
Solid - the peanuts (representing particles or molecules) are close together.
Liquid - turn a hair dryer on low and blow air into the bottle. There is some movement.
Gas - turn the hair dryer on high to demonstrate the faster movement of the particles or molecules.

Make Jell-O

In the past I have always made Jell-O when I was teaching the three states of matter. It starts as a solid (the powder). When you add the water the powder dissolves and it becomes a liquid.  The water is so hot you can see the steam coming off it (a gas).  Then, I poured the mixture in several ice cube trays to put in the refrigerator. I let the kids predict what would happen by the next time we looked at it.  Later that afternoon or the next day, I would take the trays out of the refrigerator and the Jell-O has turned back into a solid. Pass out plates, scoop out of the ice trays, and enjoy!

Shaving Cream Experiment for Sale at the Teaching Oasis