Which of the following is a physical change. a piece of magnesium metal formed bubbles when dropped in acid h2o became a vapor when heated a green chili rotted when left outside sodium metal burned with water

H2O became a vapor when heated because thats the only one that can go back to its normal state, which is what a physical change is.

nacl is added to the aqueous of what? ? in order to get a proper answer you have to specify the exact composition of the aqueous solution.