Question

Explain sublimation on the basis of kinetic theory.

Answer 1

1. Sublimation occurs as molecules of a substance in the solid-state go to the vapor state directly, rather than through the liquid state.
2. In terms of the kinetic molecular theory, we know that molecules are in constant random motion, even when the substance is below the melting point.
3. We also know that the average speed of the molecules (kinetic energy) is directly proportional to the absolute temperature.
4. If the molecules are below the melting point and are kept in the solid state by relatively weak intermolecular forces (compared to the strength of the covalent bonds within the molecule) then sometimes a molecule will have enough energy to break those intermolecular bonds and go into the vapor state.
5. This process is known as sublimation.