Consider two iron cubes, one at 10 ° C and one at 30 ° C, that are not in direct contact, because between them was placed a layer of another material.
If because of this, the thermal equilibrium is retarded, we say that this material is a thermal insulation.
There is no perfectly insulating material that completely prevents heat exchange, but there are materials that, in practice, greatly slow the heat exchange. These materials are good thermal insulators. These include cork, Styrofoam, wood, air, ceramics, glass and glass wool.
If, on the other hand, the layer of material placed between the cubes allows heat exchange, as if the cubes were directly in contact, then the material is called thermal conductor.
Although there is no material that conducts heat perfectly, there are several examples that act as good heat conductors. Some of them are silver, copper, aluminum, steel and brass.
The concept of thermal conduction
When heat exchange occurs between two bodies in direct contact or joined by a heat-conducting material, the process is called thermal conduction.
In the thermal conduction process, there is no movement of material from one body to another. There is only energy transport, ie heat transfer.