Conduction and Convection

We will cover conduction and convection together as these two methods of energy transfer need particles to transfer energy, unlike radiation.


Both conduction and convection are methods of energy transfer that need particles to transfer energy. However, in solids, energy is transferred by conduction.

In solids, energy is transferred by conduction

When a substance gets heated, the particles in the substance vibrate much more and begin to bump into each other. This eventually causes all of the particles to vibrate more vigorously. When this happens, energy transfers along the substance via conduction.

The diagram below represents the arrangement of atoms in a solid and the colour represents how hot each atom is.

  • The more red the atom is, the more heat energy the atom has
  • The more blue the atom is, the less heat energy the atom has

As the atoms start to vibrate more, they collide with neighbouring atoms, transferring heat energy.

For example, when a metal spoon is placed into a hot drink, the whole spoon ends up becoming hot.

Conductors and insulators

If something is a good conductor, then it is a bad insulator just as good insulators are bad conductors. This is because conductors transfer heat easily and insulators do not transfer heat easily.

Good conductors/poor insulators

An example of good conductors is metals.

When heat passes through a substance, it has to pass from particle to particle. Solids are usually the best conductors because their atoms are very close together. This means that when the atoms vibrate, they instantly collide with neighbouring particles.

Good insulators/bad conductors

Some examples of good insulators are:

  • Plastic
  • Air
  • Wood
  • Rubber

Some good insulators are bad conductors because their particles are more spaced out. Therefore, it is more difficult to transfer energy to neighbouring particles because they are further away.


Convection happens in liquids and gases, in which the particles are far apart and are free to move randomly. Although the particles in liquids are closer together than gases, they are still able to move and flow.

Near the source of heat, the particles have a lot of thermal energy, so they vibrate and move much faster. This leads to the particles moving further apart, making the liquid or gas less dense.

It is important to remember that the particles do not become less dense, as they do not change in size, only the overall gas or liquid becomes less dense.

1. The moving particles with a lot of thermal energy rise and transfer energy to the particles at the top, replacing the particles with little thermal energy.

2. Particles at the top, which as a whole are cooler and denser, fall to take the place of the high-energy particles.

The constant cycling of particles is called a convection current. It is a constant current of particles, rising and falling with the transfer of energy to colder regions.

Let’s look at an example with water heating in a pot:

1. The pot is heated from the bottom.

2. The particles at the bottom of the pan start to vibrate more as they are heated.

3. These particles then transfer heat energy to other areas of the pan and to the water molecules at the bottom of the pan.

4. The water inside the pan is being heated using convection, which is why convection currents start to form.