Question

What is the difference between molecular motion and diffusion?

Answer 1

Difference between Molecular Motion and Diffusion are as follows:

Molecular Motion	Diffusion
Molecular motion is the random movement of molecules in a substance without any applied external influence.	Diffusion is the movement of molecules from a high concentration region to a low concentration region.
Molecular motion is random	Diffusion always occurs through a concentration gradient
Molecular motion is affected by external factors such as temperature and pressure.	Diffusion is affected by factors that affect the concentration gradient.
Molecular motion cannot be predicted due to molecular collisions. Thus the there is no final stage since molecules are always in random motion.	After diffusion, a solution with uniformly distributed solutes is created.

Molecular Motion: it is the movement of molecules here and there inside the boundary of a substance. This motion of molecules causes molecular collisions. These collisions cause the molecules to bounce on each other.

Molecules that build up matter is always in constant motion. But the nature of this motion is different from each other in three states of matter. In solid substances, the molecules are tightly packed. Therefore, molecules in solid materials exhibit minimum motion. But in gaseous compounds, the molecules can move freely because there is no packing of molecules in gases. In liquid matter, molecules observe a limited but considerable motion when compared to solids.

When an external influence is generated, the motion of molecules can be changed. For example, when the temperature of a gas is increased, the internal energy of the gaseous compound increases, resulting in a high kinetic energy. Then the molecules begin to move faster than before. Similarly, when pressure is applied to a gas, the gas tends to be compressed. Then the volume that is available for gas molecules to move is decreased. As a result, the movement is limited.

Diffusion:  The diffusion occurs until the concentration of the whole system becomes equal at every point. In other words, diffusion occurs until the amount of molecules in the low concentration region and the high concentration region becomes equal. Molecules spread everywhere evenly in a solution through diffusion.