Welcome! I really hope you enjoy my video! 
For this experiment, I had my (sassy) younger sister as my assistant and we used a corn kernel to demonstrate floating and sinking. 
Our prediction was that the corn kernel would sink due to its high density but if we popped the corn into popcorn, the popcorn would float as the density levels would decrease with the corn kernel filling up with air. We were correct.
Our alternate conception was that if the popcorn was filled with water, it would sink as the density levels would increase again due to the water in the corn. We were incorrect, we had come to a realisation that the popcorn would still float!