Which of the following action produces a chemical change?
boiling water
burning the rice
adding salt to hot water
melting butter on cooked rice

Nope. correct answer is "burning the rice". why? adding salt to hot water is the phenomenon of solubilization which is a physical process. ions are indeed coated by water molecules but it does not change the chemical structure, but only physical. solid salt is also made of ions.
burning the rice leads to chemical reaction of combustion. carbohydrates are turned into CO2 and pure carbon and that's why burned rice has black colour.

Air occupies

What is your question then