Final answer:
Microwaves heat organic materials primarily through absorption and rotation. The microwave photons are absorbed by water molecules, causing an increase in rotational energy which is converted into heat, heating the substance from within.
Step-by-step explanation:
The mechanisms by which microwaves heat organic materials are absorption and rotation. When microwaves, which are a form of electromagnetic radiation, interact with organic matter, the microwave photons are absorbed by water molecules within the substance. This absorption causes an increase in the rotational energy of the water molecules, which in turn heats up the substance as the energy is converted into heat. Unlike conduction or convection, which involve physical contact and the movement of fluids respectively, microwave heating is most closely related to radiation heat transfer, where energy is transferred through electromagnetic waves.
Microwave ovens make use of this absorption mechanism to rapidly heat food by producing electromagnetic radiation in the radio portion of the spectrum. The water molecules in the food absorb these microwaves and increase in rotational energy, which then disperses as heat through the food. This method of heating is efficient and does not require the matter to be stationary or a fluid to facilitate heat transfer.