system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What determines if something is "microwave safe"?
gpt
Microwaves work by causing polar molecules to continuously reorient themselves in the oscillating electric field which causes them to heat up. This field is the result of the microwaves themselves being emitted. One of the most abundant and polar molecules in existence is water. As such, microwaves can be thought of a primarily heating the water in the object and then that water transfers heat to the rest of the object. The tricky thing with plates, bowls, etc. is that some of them are made up of "hydrous" materials, meaning that there is water bonded to their constituent molecules. When this water continuously reorients itself in the electric field, it messes with the constituent molecule and can cause the object to be ruined. Or it can simply heat up the object to the point that it is dangerous to touch. This isn't restricted to water, so if the object has some other polar molecules in its composition, it may still be subject to this phenomenon. It is just most common with water.