This teacher did this for a preschool lesson, but it can be adapted for older kids. They could drop or open the balloons and observe what happens to the solid liquid and gas inside it. This would help identify the properties of solids, liquids and gases.
compoundchem: Added a newer, poster friendly version of the Metal Ion Flame Test Colours graphic to the store today! You can view the original post here, which includes an explanation of the origin of the colours.