Heat Conduction in Solids and Liquids
by Arthur Rytis
Here is a simple way to visualize how heat travels through solids and liquids. Heat applied to one end of a substance causes its particles to vibrate faster. These particles, in turn, bump into particles nearby, and make them vibrate. Eventually the extra energy of vibration works its way to the other end of the substance, as the particles bump into their neighbours.
This explains why gasses do not conduct heat very well; their particles are so far apart that the heat can't be transferred by particles bumping into each other.
It also explains why solids conduct heat faster than liquids. In both these substances, particles are about the same distance apart, so distance is not the reason that liquids conduct heat slower. It has to do with how the particles are arranged in the substance. Let's use some pictures to explain it ...
Imagine these people are particles in a solid. Notice that every particle is joined by forces to nearby particles. Molecules in a solid are locked in place and are not free to move around. If you apply some heat (from Kenneth at the right), the particles there will vibrate faster, and the vibration quickly works its way through the solid, because all the particles are interconnected and locked in place. In this experiment, Mandy and Jess (on the left) were knocked off balance within a second.
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Imagine these people are particles in a liquid. Every particle is on its own and free to move around, as long as it stays within the group (the liquid). In this case, the vibration (heat) applied by Kenneth moves more slowly through the particles, since they must actually make contact in order to transfer the vibration, and are free to move, carrying the energy off in various directions within the fluid (Scott moving sideways). In this experiment, the vibration never did reach Mandy and Jess.
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