Heat conduction is the transfer of internal energy (microscopic kinetic and potential energy) from a region of higher temperature to one of lower temperature by the interaction of particles like atoms, molecules, ions or electrons in the intervening space. Conduction can only take place within an object or material or between two objects that are in direct or indirect contact with each other.
There are four factors that affect the rate of heat conduction: temperature difference, length, cross-sectional area and material.
Conductivities vary for each type of material. It is greatest for metallic solids, lower for nonmetallic solids, very low for liquids and extremely low for gases. Conduction is greater in solids because of the closed and fixed space between atoms. This helps transfer energy between them by vibration. The best ordinary metallic conductors are silver, copper, gold, aluminum, beryllium and tungsten. Fluids are less conductive due to the large distance between atoms, which leads to fewer collisions between atoms.
Conductivity of gases increases with temperature. This is due to the increasing pressure from vacuum up to a critical point that molecules of the gas may be expected to collide with each other before they transfer heat from one surface to another. After this point, conductivity increases only slightly with increasing pressure and density.