# Thermal conductivity

The thermal conductivity is a term directly related to the heat , which is a type of energy that is produced when vibrating molecules of a body thus causing temperatures to rise. Bodies have the great ability to transmit heat from one place to another and it is this property of materials that is known as thermal conductivity .

## What is thermal conductivity?

Thermal conductivity is a type of physical property of matter that can describe the ability of a particular element to transfer the heat through the direct contact without any exchange of matter.

• Definition
• Thermal conductivity coefficient
• What is it for
• What factors influence thermal conductivity
• High thermal conductivity materials
• Low thermal conductivity materials
• Importance
• Examples

## Definition

This term refers to the property that elements have of being able to transmit the generated heat or electricity. When the material can transmit heat, then it refers to thermal conductivity . This characteristic implies that a matter can pass heat to a body that has a lower temperature than it. It is a type of internal energy exchange that also combines kinetic and potential energy . When the different molecules that are part of an object are heated, they gain the possibility of moving and colliding with each other in order to transmit the thermal energy. towards other molecules.

## Thermal conductivity coefficient

This type of coefficient helps us to express the flow or the amount of heat that can pass through a surface of a material and is represented by the symbol (λ).  It is an empirical statistical formula and to measure it the International System of Measurements is used, so it is used in watt / meter x kelvin. It can also be measured in kilocalorie (hour × meter × kelvin) (kcal / (h · m · K)) and in British Thermal Units or BTU (hour × foot × Fahrenheit) (BTU / (h · ft · ° F)) . Its formula is the following:

(W / m K)

## What is it for

Thermal conductivity is used to be able to make descriptions and to know the capacity of a certain material to transfer heat through conduction. It is used to determine what types of materials can be used depending on the purpose to be achieved. They also provide protection against heat and fire, in the case of those with low conductivity.

## What factors influence thermal conductivity

The thermal energy that bodies have can be transmitted depending on several factors that directly influence, among which we have:

• Conduction : it is the transmission of heat through contact without there being any type of transfer of matter.
• Convection : in this case, the transmission of heat by contact includes the passage of the matter that carries the heat.
• Radiation : in it the passage of heat is given using the emission of electromagnetic waves or photons.

## High thermal conductivity materials

One of the best materials that have a high level of thermal conductivity are metals which can pass heat very easily. These materials include for example iron , copper and aluminum . An example of them would be the pans that are used in the kitchen which when they come into contact with the fire can heat up quickly.

The liquids are also considered good conductors because they have the ability to produce currents between the molecules that make up water and thereby mix the cold molecules with hot achieving the same level in the temperature.

## Low thermal conductivity materials

Among these materials we can mention adiabats such as wool , plastic , fiberglass , wood and cork . They are widely used to maintain stable temperatures in places where climates are very cold. We can mention as examples the wooden handles that are placed in the pans to avoid burns.

## Importance

Thermal conductivity is important to know because the selection of a series of materials depends on this depending on the function that is needed. In daily life, energy saving has become very relevant because it brings great benefits that include reducing energy consumption , costs and improvements in various places such as work spaces. Thanks to conductivity, it is then possible to know which types of materials become the best option in order to avoid thermal conduction and thus create materials that are resistant to heat.

## Examples

Some materials and their respective thermal conductivity are mentioned as examples below.

• Copper: 0 W / (Km).
• Cork: 0.03 to 0.04 W / (Km).
• Water: 0.58 W / (Km).
• Wood: 0.13 W / (Km).
• PVC: 0’16 W / (Km).
• Iron: 2 W / (Km).
• Glass: 0.6 to 1.0 W / (Km).
• Rock wool: 050 and 0.03 W / (Km).
• Cement: 25 W / (Km).
• Graphite: 700 to 195 W / (Km).
• Lead: 35.0 W / (Km).
• Clay: 0.121 and 0.714 W / (Km).