Molecular Diffusion in Fluids

Molecular diffusion is considered as diffusion which states the thermal movement of particles including gas and liquid at a temperature which is beyond absolute zero. The movement rate is a function which comprises temperatures, particle size, and fluid viscosity. It generally describes the net instability of molecules initiating from higher concentration and going to lower concentration regions. It further states that as soon as the concentrations become equal then the molecules resume their movement. As there is no availability of concentration gradient then it ceases the molecular diffusion process and is thus governed by a self-diffusion process which comes from random movement of molecules.

Molecular diffusion: Explanation

Molecular diffusion refers to the movement of molecules at a thermal stage that is being flowed at a temperature exceeding entirely zero. It states if the size of molecules and the mass increases it will cause the rise of molecular diffusion in the molecular movement within fluids. It further states that elevation of temperature might cause rise in the length of free path, growth in free motion velocity and a sudden decrease in the collision rate between the particles.

Diffusion in solids: Process

Gases which are present in solid often diffuse as atoms which migrate through interstitials of crystal lattice and are thus observed for ions and atoms within a radius which is much smaller as compared to atoms of base substance that constitutes the solids. Solid impurities which are being diffused arise by an interchange of atoms and vacancies by migrating atoms through interstitial as well as interchange of two distinct atomic sites directly and the simultaneous migration of various atoms. Each displacement needs to impart a requisite amount of energy to the particle which implies that diffusion is exceedingly sensitive in order to elevate the temperature which manifests in the exponential vulnerability of temperature. Thus it can be stated that diffusion in solids is extremely slower than the diffusion in liquids. Examples of solid diffusion can be spreading chock powder on a plane of blackboard as well as settlement of household objects by spreading air dust.

MolecularDiffusion: Importance

Molecular diffusion plays a critical role in the diffusion of fluids as it is responsible for the flow of molecules starting from higher concentrations and ending with lower concentration regions. It states that the coefficient of diffusion is multiplied by gradients in order to attain flux related to chemical species as well as concentration gradient which makes the molecular flow at an equilibrium stage which implies that the division of molecules become uniform. Although the coefficients vary from a factor of 10 under distinct conditions as well as small differences are sometimes crucial in the process of combustion. It might be assumed that molecular and thermal diffusion varies inversely concerning pressure and atmospheric pressure which is about 0.1 cm2/s in room temperature. Molecular diffusion coefficient states the faster movement of diffused materials from one region to another. It states that higher is the diffusion coefficient, the diffusion rate will be faster as well it future states that diffusion coefficient in solid is slower than diffusion rate in liquids. The diffusion coefficient is a key variable in evaluating equations which includes Ficks’ first and second laws. Fick’s first law states that diffusion flux starting from higher and going till lower concentration is proportional to concentration gradient that is J∝dy/dx in which j refers to diffusion flux, dy is concentration change, dx is position change. Fick’s second law is the relation between concentration gradient change of time and particles which implies that dy/dx= D* d2y/dx2

Conclusion

Diffusion of molecules in fluids states the flow of specific particles which can be either liquid or gas at a temperature that exceeds absolute zero. It concludes the movement of particles from higher to lower concentration which further signifies that if concentrations achieve equilibrium point then the particles will cease as there will be no concentration gradient. It further concludes that it is controlled by a self-diffusion process which arises from molecular motion resulting in moderate mixing of material so that the molecule’s distribution can be uniform. It further states the molecular motion which still results in dynamic equilibrium.