In this demo, food coloring is added to a stirring beaker of water to create a tornado of color. This could be used as an example of a physical change, or to demonstrate the importance of properly mixing solutions.
CO2 gas from subliming dry ice gets caught in a soapy solution creating a column of bubbles. When the bubbles are popped, the “fog” that we see is condensed water vapor, not carbon dioxide gas.
When ammonium nitrate is dissolved in water it feels cold, which indicates an endothermic reaction.
NH4NO3 (s) → NH4+ (aq) + NO3- (aq)