system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If microwaves are tuned to the resonant frequency of water, why is it that heating up a bowl of soup results in the bowl being so hot it burns my hand while the soup itself remains tepid?

Writing this as I'm nursing a sore hand and eating cold soup.
gpt
In physics there is a concept called specific heat.  It is a measure of the amount of heat energy it takes to raise the temperature of a substance, specifically the amount of energy it takes to raise 1 gram 1 degree centigrade.

It happens that water has easily the highest specific heat of any common substance you are likely to find in your home, including anything a bowl is likely to be made out of.  The water in food may actually absorb more energy from microwaves than the container, but still heat more slowly because the container takes far less energy per gram to increase in temperature.