Understanding Conduction

- Conduction is a process by which heat energy is transferred through a solid.

The particles in a solid are held together in a fixed position, but they can still vibrate.
When heat is applied to a material, particles near the heat source will vibrate more and then pass this extra kinetic energy onto their neighbouring particles.
This process is repeated throughout the material until the heat energy is spread evenly.

Metals as Good Conductors

Metals are excellent conductors of heat. This is primarily because metals have free electrons that can move through the metal and transfer energy.
These free electrons collide with atoms and other free electrons, passing on the kinetic energy and causing them to vibrate more strongly.
The presence of these free electrons in metals makes the process of conduction faster in them compared to other materials.

Materials that are poor conductors of heat are referred to as insulators. Examples of these are wood, plastic, and glass.
In insulators, the particles are not easily able to pass on their vibration energy to their neighbouring particles. This is due to the lack of free electrons.
This property makes insulators useful in preventing heat loss or gain in objects or areas. For example, housing insulation keeps heat inside a home in winter.

The rate of conduction depends upon the temperature gradient; the greater the difference in temperature between two sides of a material, the more rapid the rate of conduction.
Material type also has a big effect. As mentioned, metals are very conductive, while insulating materials are not.
Thickness of the material also plays a role. The thinner the material, the faster heat will be conducted through it. Thick materials tend to slow the process of conduction due to the longer distance the heat energy has to travel.

Understanding conduction can help when choosing materials in home construction and in the design of appliances.
For example, the handles of cooking pots are often made of plastic or wood. These are both poor conductors of heat and prevent the heat from the pot being conducted onto the person cooking!
In general, materials are chosen based on their conductive properties depending on whether we want to keep heat in or out.
A good knowledge of conduction can help save energy and money by making appropriate choices for insulation and appliances in the home.