microwave oven

[KathChem82]

we usually cook or reheat food or beverages inside a microwave oven.why is it that a food is cooked inside the microwave oven without it heating the container of the food?

[NanoMachine]

The microwave is tuned to excite the chemical bonds in water molecules - much like a car radio is tuned to pick up different stations. When you tune the radio to a specific frequency, you only hear one station. When a microwave oven is tuned the way kitchen microwaves are, they give nearly all of their energy to water molecules. So food, which is full of water, heats up. Containers, which don't contain water, don't heat up so much.

[KathChem82]

thanks. And why is it that after heating, water for example, you will notice that sometimes the water burst out of the container. It's like observing a violent reaction in chemical experiments.