A microwave oven works by emitting electromagnetic waves, specifically microwave radiation, which excite water molecules in the food, including liquid water. When microwave radiation encounters water molecules, it causes them to rotate rapidly, aligning themselves with the alternating electric field of the microwaves.
The rapid rotation of water molecules generates friction, and this friction results in the conversion of microwave energy into heat. Essentially, the energy from the microwaves is absorbed by the water molecules and transformed into thermal energy, which raises the temperature of the water.
As the water molecules heat up, the temperature of the liquid water increases, leading to boiling if the energy input is sufficient. This is why microwaves are efficient at heating or boiling liquids like water.
It's important to note that the heating process in a microwave is selective, as it primarily affects water molecules. Other materials, such as ceramics, glass, and certain plastics, may not absorb microwaves as effectively and may remain relatively cool while the water in the food or container heats up.
The ability to heat liquids quickly and efficiently is one of the reasons why microwaves are commonly used for tasks like heating water for beverages, cooking soups, and other liquid-based food items.