Why is steam so efficient when cooking food and can you explain how so much heat is released when the steam changes phase, i.e. condenses?
Steam is the gaseous form of water and consists of independent water molecules. When steam comes in contact with relatively cool food, the water molecules have the opportunity to stick to one another and the steam condenses into liquid water. While most small molecules bind relatively weakly to one another, water molecules bind remarkably strongly. They form hydrogen bonds, in which negative charge on the oxygen atom of one water molecule attracts positive charge on a hydrogen atom of another water molecule. Water’s hydrogen bonds are so strong that water remains a liquid well above room temperature while most other small molecules (carbon dioxide, methane, nitrogen, oxygen, etc.) are gases even at very cold temperatures. So when water molecules condense from steam to liquid, they form strong bonds with one another and release a great deal of energy. This energy takes the form of heat and it quickly raises the temperature of the food on which the water is condensing. That’s why steam cooks food so quickly and efficiently.