diffuision

Diffuision is not a standard term in science; it is likely a misspelling of diffusion. Diffusion is the net movement of particles from regions of higher concentration to regions of lower concentration, driven by random thermal motion. It occurs in gases, liquids, and solids and does not require external energy (it is a form of passive transport).

In biological systems, diffusion governs the exchange of gases like oxygen and carbon dioxide and the distribution of small molecules across cell membranes. Diffusion can occur directly through the lipid bilayer (simple diffusion) or via membrane proteins that facilitate transport (facilitated diffusion). It contrasts with active transport, which requires cellular energy to move substances against a concentration gradient.

The process is described quantitatively by Fick's laws. Fick's first law states that the diffusive flux is proportional to the negative gradient of concentration: J = -D ∇C, where D is the diffusion coefficient. Fick's second law describes how concentration changes over time: ∂C/∂t = D ∇^2 C, assuming a constant D. The diffusion coefficient depends on factors such as temperature, the viscosity of the medium, and the size and shape of the diffusing particles.

Factors influencing diffusion include temperature (higher temperatures increase molecular motion and D), medium viscosity, particle size, and the presence of barriers or channels. Classic examples include the spreading of a dye in water, the scent of a perfume diffusing through air, and gas exchange in lungs.

Applications span chemistry, biology, environmental science, and materials science, where diffusion models help predict mixing, transport through membranes, and the behavior of pollutants or dopants in solids.