How come we can smell solids?

Answer

Dear Eric,

indeed that you can smell a substance means that individual molecules or particles of this substance have entered your nasal receptors and in this way give a signal that we then call a certain smell. So if you smell something, it has entered your nose through the air, as a gas phase.

Your question then is, how come a solid can be smelled. Now that has to do with something that you undoubtedly learned a long time ago about states of aggregation and equilibria therein and if you put it all together in one diagram you will find all the possibilities in the phase diagram of that substance. You will then see that there is always an area where equilibrium is possible between the solid phase and the gas phase directly. In other words, even well below the boiling point of a substance, particles can pass directly from the solid phase to the gas phase. You can understand this best if you know that for a molecule or a particle there is some kind of escape energy that tears it away from the bonding forces that exist between the solid state particles. Furthermore, the energy distribution between the particles is not uniform but there is a distribution of energies and consequently it can perfectly be the case that at any temperature, there are particles that currently have just enough energy to escape and thus through the gas phase to your nose. How many there are depends on the temperature, the higher the temperature the more there are and the easier it is to smell it. A second factor is the bonding forces between the particles in the solid phase, the greater these are, the smaller the number of particles in the gas phase at a given temperature, the less easily you can smell them. For example, you cannot smell steel (strong binding forces), you can smell frozen fuel oil, even at relatively low temperatures (weak binding forces).

I hope this helps you further.

Regards