Food is made up of all sorts of chemicals. Cooking just heats up those chemicals to make them change in some way.
Think of an egg egg β when eggs are raw, theyβre all runny and gloopy. They wouldnβt be very tasty next to some bacon β yuck! As it heats up, you can see the transparent white is changingβ¦ and the yolk is getting hard.
There are long chains which are proteins β and the links are amino acids. Heat maked the chains break and reconnect in a different way. It changes pretty quickly!