Have you ever wondered why when putting food in the microwave or cooking something on the glass ceramic, the plate or the pot heats up much more and much faster than the food it contains? Or why is it so much easier to burn yourself with a hot iron bar than with a wooden branch?
This type of situation finds its explanation in what is known as the property of heat conduction , which is just another form that energy is capable of adopting. Through conduction, heat is transferred by contact from bodies that are hotter (that is, those that are at a higher temperature and, therefore, house a greater amount of energy at that time) to those that are colder ( that is, those that are at a lower temperature, since cold is the absence of heat energy).
When the hot body comes into contact with the cold body, the exchange begins to take place and the molecules of the second begin to move faster each time – accumulating more energy – while those of the first suffer the opposite effect. This is because energy is neither created nor destroyed , it is only transformed. Therefore, the exchange between one and the other body will continue until both reach what is known as thermal equilibrium .
And how this transfer of energy happens will depend on several factors. First, the thermal gradient , a physical quantity that describes in what direction and by what percentage the temperature changes most rapidly around a particular location and whose unit of measurement is the kelvin (temperature) per meter (length) (K / m ).
Secondly, the thickness and length of the bodies come into play (their longitudinal and cross section): generally, a body made of the same material as another of greater thickness will heat up more easily than the latter. In other words, it will require less amount of energy to heat up. And thirdly, the type of material that each body is made of has a significant influence. This makes the plate or pot heat up more easily than a chicken fillet. Each material has a heat conduction coefficient that, the higher it is, the easier it is to heat indicates that the material has.
Thus, the coefficient of heat conduction in silver is 100 and other metals, such as copper, tend to also have a high coefficient, which makes them good conductors of heat. Fat, meat, wood or cork have much lower coefficients (even below unity), being poor conductors and even good insulators. In fact, it is one of the reasons why humans and animals manage to maintain a certain amount of heat in our body. Air, to top it all off, has a coefficient of 0.006, making it an exceptional insulator.
