Heat (Thermal) Energy and Heat Transfer


Conduction is the transfer of energy from one atom or molecule to another atom or molecule.

The atoms in a substance are always vibrating. When heat is applied to a substance the heat energy is given to the atoms and they vibrate and move faster and so their kinetic energy increases. The vibrating atoms bump into neighbouring atoms and pass on their kinetic energy. These atoms then pass on their kinetic energy to atoms close to them and so on. In this way the heat energy moves through the substance.

Conduction takes place in solids, liquids and gases, but works best in solids as their atoms/molecules are located closer together.  Metals are the best solids for conducting heat. Metals have tightly packed atoms which can easily pass on their kinetic energy and also have free moving electrons. These electrons can move from the hot part of the metal to the colder part transferring the energy more quickly.

Poor conductors or insulators do not possess free moving electrons.


The animation below shows heat transfer in a metal by conduction:

The heat from the flame is given to the atoms and they begin to vibrate faster. The atoms collide with the atoms close to them and in this way the heat flows from the hot end to the cold end. As the distance from the flame increases the temperature decreases by a proportional amount.