Question

Which of the following diffuse fastest and which the slowest? Solid, Liquid and Gas. Give reasons for your answer.

Answer 1

Hint: Process of diffusion is defined as the movement of solute particles from their higher concentration region to their lower concentration region. The process of diffusion does not require any semi-permeable membrane as in osmosis.

Complete answer:
Process of diffusion is observed in all the three phases of matter which are solid, liquid and gas. Diffusion is spontaneous process which depends on many factors like particle size, mass, charge on the substance,
Solid is composed of its constituents’ particles or atoms which are packed closely to each other with the help of strong interactive forces like covalent force, electrostatic force of attraction. Due to high molecular attraction between the atoms of solid material they are not free enough to undergo the diffusion quickly.
As we know, the attractive forces among the constituent’s atoms in liquid is somewhat lower than the solid. In the case of liquid particles they have some degree of freedom to move with respect to another particle but within a certain limit range. Beyond that limit particles are not allowed to move freely therefore, liquid shows a tendency to diffuse faster than solid material but slower than gaseous material.
In the case of gas, we know that all the constituents of gas are allowed to move randomly with respect to another particle due to their high kinetic energy. There is a very low or negligible magnitude of force of attraction between the particles of gases. Therefore, they are free to go under the diffusion process.
The rate of diffusion is slowest in the case of solid due to presence of strong intermolecular attractive forces and rate of diffusion is fastest in the case of gas due to absence of any strong attractive forces.
$\Rightarrow$ Fastest diffusion occurs in gas and slowest diffusion occurs in solid.

Note:
Process of diffusion is difficult to stop or reversed because this is a spontaneous process which continues until the ultimate equilibrium is reached. The process of diffusion is an energy independent process.