Conduction

*️⃣ Conduction is the transfer of thermal energy through a substance without the bulk movement of the substance itself. It occurs primarily in solids, via the vibration of atoms or molecules and, in metals, via the movement of free electrons.

Mechanism in Non-metals

In all solids, the particles (atoms or molecules) are held in fixed positions in a lattice and can only vibrate about their equilibrium positions. When one end of a solid is heated, the particles at that end gain energy and vibrate more vigorously. These particles collide with neighbouring particles and transfer some of their kinetic energy to them. Those neighbours in turn vibrate more vigorously and pass energy further along the solid. In this way, energy is conducted along the material from the hotter end to the cooler end.

This process is relatively slow in non-metals such as glass, wood, and plastic, because the only mechanism for energy transfer is particle vibration. These materials are therefore poor conductors of heat and are used as thermal insulators.

Mechanism in Metals

Metals are much better conductors of heat than non-metals because they have an additional, much faster mechanism: the movement of free (delocalised) electrons. In a metallic lattice, a large number of electrons are not bound to any particular atom and are free to move throughout the material.

When the metal is heated, these free electrons in the hot region gain kinetic energy and move rapidly through the lattice, travelling to cooler regions and colliding with atoms there, transferring energy much more efficiently than vibration alone. This is why metals feel cold to the touch even at room temperature — they conduct heat away from your hand very quickly.

Mechanism	Occurs in	Description
Particle vibration	All solids	Vibrating particles collide with neighbours, passing energy along the lattice.
Free electron movement	Metals only	Delocalised electrons gain energy and rapidly transport it to cooler regions.

Good and Poor Conductors

Materials are classified as either good conductors or poor conductors (insulators) of thermal energy based on how readily they allow energy to pass through them.

Good conductors — all of which are metals — include copper, aluminium, and steel. Poor conductors (insulators) include wood, glass, rubber, air, and most non-metals. Air is an especially effective insulator because its particles are far apart and rarely collide, making it difficult to transfer energy by conduction alone.

Everyday Examples

A metal saucepan conducts heat from the stove burner to the food inside due to free electron movement and lattice vibration.
Wooden or plastic handles on cooking pots are used because these materials are poor conductors, protecting the user's hand from the heat.
Double-glazed windows trap a layer of air between two glass panes, reducing energy loss by conduction because air is a poor conductor.
Fiberglass insulation in the walls and roof of buildings uses trapped air pockets to minimise energy loss by conduction.