What is conduction?
If you place a cold object near a hot object (for example, a metal rod into a flame), it will get hot. This is because heat energy will be transferred from the hot object to the cold object.
In solids, the process of heat transfer is called conduction. This process does not occur in liquids or gases - heat transfers in a different process in those states of matter (called convection).
How does conduction occur?
Solids transfer heat because they have particles that are very close together. Making one end of the solid slightly hotter than the other end means that the particles in the hot area of the solid will move faster than in the cold area. The faster-moving particles will then collide with the slower-moving ones, transferring some of their energy. This makes the slower particles speed up, increasing the temperature of that cold region. The process then repeats and continues until all of the particles in the solid are moving at the same speed and the whole object reaches the same temperature.
The easiest way of visualising conduction is shown in the diagram above. Think of all the particles in a row, bumping into each other in a long line. Remember that heat always flows from hot to cold. It is never the other way around.
How do you speed up conduction?
Metals are the best conductors of heat as they have many free electrons. So, if you wanted to manufacture something that could transfer heat very quickly, such as the shelf of an oven, you would make it out of metal. (Non-metals are generally poor conductors, called insulators, which is why you stir hot sauce and boiling water on the cooker with a wooden spoon. You don't want the heat energy to rapidly transfer to your hand).
To increase the rate of conduction, you need a greater temperature difference between the hot and the cold object. For example, if two solid objects were placed next to each other and there was only one degree difference in their temperatures, the heat would transfer slowly. If, one the other hand, their temperatures differed by 100 degrees, then the energy would rapidly transfer, as the particles in the hot object would have much more energy than the cold one, and they would collide with much more speed.
Now that you have seen the idea of conduction, let's have a go at a set of questions on the subject!