What is a good hypothesis for a dry ice project?

a hypothesis for hot ice would depend on the ingredients you use and the temperature

my example would be..... " i boil 1L vinegar and add 4 tsp on baking soda for 30 minutes until a crust forms and then i cool it in the fridge for 40 minutes. then when i touch it it instantly turn into ice".... u could also do the experiment where u use sodium acetate or the one where you use hand warmers.