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    Conduction is the transfer of heat by diffusion and collisions of particles due to a temperature gradient on a surface. The transfer of kinetic and potential energy of the particles is referred to as internal energy. Conduction can occur in all forms of matter such as solids, liquids, gases and plasmas. It can only occur between two phases which are in contact with each other. 

    Gases are less conductive than other phases. This is due to the large distances between atoms in a gas. Few collisions between atoms results in less conduction occurring. Conductivity of gases increases with temperature. Conductivity also increases with increasing pressure to a critical point that the density of the gas is such that molecules of the gas may be expected to collide with each other before they transfer heat from one surface to another.

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