What keeps a colloid homogeneous?

A colloid is a mixture where tiny particles are dispersed throughout a continuous medium, and it maintains a homogeneous appearance thanks to a phenomenon known as Brownian motion. Brownian motion refers to the random, erratic movement of particles suspended in a fluid due to collisions with the molecules of the surrounding medium. This constant motion prevents the particles from settling down, helping to keep the mixture uniform and evenly distributed.

In contrast, osmosis involves the movement of solvent molecules through a semi-permeable membrane from an area of lower concentration to higher concentration, which does not directly relate to the homogeneity of a colloid. Similarly, diffusion refers to the process of particles spreading from an area of high concentration to an area of low concentration, which applies more to the initial mixing of substances rather than maintaining the stability of a colloid. Viscosity is a measure of a fluid's resistance to flow, influencing how easily it moves but not specifically addressing the dispersal or homogeneity of particles within a colloid.

Thus, Brownian motion is the key factor that helps maintain the homogeneous nature of colloids by keeping their particles in constant motion and preventing them from aggregating or settling, which ensures the mixture remains even throughout.