The thermal conductivity of a particular product can be an essential property to understand, especially if working with heat on a regular basis. Glass, due to its low thermal conductivity, is an idea material to use in applications that require high heat.

Definition of Thermal Conductivity
Thermal conductivity is a value that is given to a material based on the ability of heat energy to move through the substance.

Thermal Conductivity and Material Types
Gasses have a relatively low thermal conductivity compared to solids since they can only transfer heat through collisions with other gas molecules. Liquids and solids have higher thermal conductivity as heat can transfer much easier through them. The vibrations of the crystalline lattice of metals and the ability of their electrons to move can allow for much easier transfer of heat and higher thermal conductivities.

Thermal Conductivity of Glass
Glass, depending on which type, has a relatively low thermal conductivity; its value is 0.8 compared to that of steel, which is 46, and copper, which has a value of 401. These numbers make sense if you think about heating each of these materials and how fast each warms up.

Thermal Conductivity and Phonons
In physics, the particles that are associated with lattice vibrations are called phonons. Just like photons are particles of light, phonons are particles of energy that relate to a mode of vibration.

Practical Application of Thermal Conductivity
The University of Virginia puts it like this, “Heat moves very quickly through a metal spoon (it has a high thermal conductivity), for instance: leaving one end of a spoon in boiling water will make the entire spoon hot very quickly. The entire spoon becomes hot, not just the spot in the boiling water. On the other hand, heat moves very slowly through the insulation in your house. When it is very cold outside, the heat from your house moves slowly from one side of the insulation to the other. This helps keep the heating costs of your house down.”


By Philip J. Carlson, eHow Contributor

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