Salt disperses through water because ions become surrounded by water molecules. Oil and water tend to separate because their molecular interactions differ, but emulsifiers can stabilize tiny droplets of one phase inside the other.
Heating food does several things at once: water evaporates, proteins unfold and reorganize, starch absorbs water, and browning reactions create new aromas and colours. Cooking is rarely one chemical reaction.
The tools tell a materials story too. Copper and aluminium conduct heat well, stainless steel resists corrosion, and glass-ceramics can tolerate rapid temperature changes.