One experiment we did involved testing chemical and physical reactions. For the first part I gave him three white powders (baking soda, baking powder and corn starch). He added water, vinegar and lemon juice to each powder and recorded the physical and chemical changes.
Next, I gave him two white powders in baggies. One was from a "crime scene" (that was baking soda) and one was from a "suspect's shoe" (that was actually a crushed alka seltzer tablet). The Boyscout had to test them and tell me if they were the same substance or not based on their reactions.
The second experiment had to do with the correlation between changes in temperature and pressure. We heated an empty soda can in the oven for 5 minutes until it was hot. Using tongs, he then placed it open side down into a shallow dish of cold water. The change in the can is instantaneous, and got quite a reaction from The Boyscout!
We have done a few other experiments the last few weeks, but these were by far his favorites.