Thermal mass

Thermal mass is how much heat energy an object must absorb to raise its temperature, which depends on its weight and the material it is made of. Objects with high thermal mass heat up and cool down slowly. It is measured in joules per degree, for example about 360 joules per degree Celsius for a 400 gram aluminum plate.

Example: A heavy cast iron skillet takes much longer to preheat than a thin aluminum pan, but it holds its temperature better when cold food is added.