Cooking.
The Merriam-Webster definition of cooking is "to prepare food
for eating especially by means of heat".
There are 3 different methods of using heat to cook food.
When food is exposed to one (and/or more)
of these methods, the different types of molecules in food
"change their form".
That is how
food is "cooked"!
These types of molecules are: fats, sugars,
proteins, starches, and water.