Thermal conductivity
To quantify the ease with which a particular medium conducts, engineers employ the thermal conductivity, also known as the conductivity constant or conduction coefficient, "k". In thermal conductivity, "k" is defined as "the quantity of heat, "Q", transmitted in time ("t") through a thickness ("L"), in a direction normal to a surface of area ("A"), due to a temperature difference (Δ"T") [...]". Thermal conductivity is a material "property" that is primarily dependent on the medium's phase, temperature, density, and molecular bonding. Thermal effusivity is a quantity derived from conductivity, which is a measure of its ability to exchange thermal energy with its surroundings.