So I need to give an exciting thermodynamics demo based on one of the first two laws. I have found it difficult to either make it exciting enough or to make it apply to thermodynamics enough. I have a few that I have come up with but I don't think any really apply as well as I want. 1)Can crush but on a bigger scale with like a drum. Heat water in a can and then dunk it in cold water. (shows that heat flows from hot to cold 2nd law) 2)Spud gun. Giant spud gun but thats see through. Ignite gas and fire potato (Add heat and show that work is done on the potato 1st law) 3)Boiling water and liquid nitrogen. Nitrogen evaporates and makes a huge cloud due to condensing water from the air (2nd Law showing that heat again flows from hot to cold and energy is dissipated) Are any of these any good? Could do with some help.