Solid iodine crystals at the bottom of a closed test tube sublime to form iodine vapor. the vapor eventually fills the entire test tube. use kinetic molecular theory to explain the diffusion of the iodine gas and whether diffusion happens in liquids and solids.

Diffusion occurs in solid and liquid through the constant and random motion of the smaller particles called molecules of either solid, liquid or gaseous in permeable medium as witnessed in the experiment.

Explanation:

The kinectic molecular theory of matter states that the smaller particles of matters called molecules are in constant, but random motion and the degree of movement of the molecules depends on the state or phase such matter exist, which is a derivative of the total kinetic energy possessed by the molecules. This average kinetic energy of the molecules as iodine for example is proportional to the temperature of the matter.

Diffusion should be remembered as the movement of molecules of matters from a highly concentrated region otherwise called hypertonic region to a less concentrated region called hypotonic region through a permeable medium until there is an equilibrium in the system. Since diffusion is expected to involve the movement of molecules, and any matter that can exhibit diffusion is said to have moving molecules, therefore, the kinetic molecular theory of matter is proven to be accurate with the observed movement of iodine molecules in the test tube. This shows that even the molecules of solid matters are in constant random motion, this is made more convincing when these molecules migrate without the addition of external energy source like heat, which then help to understand that the natural iodine molecules are in constant random motion, as they are changed to gaseous state without passing through liquid state, a phenomenon called sublimation.