Q.Explain Brownian movement, state its physical cause, and explain how it contributes to the stability of a colloidal solution against settling under gravity.

[!TLDR] Brownian movement is the random zig-zag motion of colloidal particles caused by unequal bombardment from dispersion-medium molecules; it keeps particles kinetically stable against settling. [!ANSWER] Brownian movement = random particle motion …

Brownian movement is the continuous, random, zig-zag motion of colloidal particles observed under a microscope, first reported by Robert Brown. Its physical cause is the constant bombardment of each (comparatively large and heavy) colloidal particle by the vastly more numerous, much smaller, and extremely fast-moving molecules of the dispersion medium; because this bombardment is never perfectly equal from every direction at a given instant, the particle receives a net, randomly-changing push, producing its erratic path. This ceaseless agitation works continuously against the tendency of colloidal particles to settle under gravity, and is one of the principal reasons a lyophobic colloid, despite not being thermodynamically stable, remains kinetically stable — i.e. remains dispersed indefinitely rather than settling …

Explain the molecular-collision origin of Brownian movement, then connect it to why colloidal particles do not settle out de …

Do not attribute Brownian movement to convection currents or vibration of the container — its cause is specifically the random, u …