What is a colloid?

A colloid is best described as a homogeneous mixture where small particles are dispersed throughout a continuous medium. This is a crucial aspect because the size of the particles in a colloid ranges from about 1 nanometer to 1 micrometer, allowing them to remain evenly distributed throughout the medium without settling. The continuous medium can be a liquid, gas, or solid, which further highlights the versatility of colloidal systems.

In colloids, the dispersed phase (the small particles) does not dissolve like in a true solution; rather, these particles are suspended and can affect the physical properties of the mixture. This suspension can create various observable phenomena, such as the Tyndall effect, where light scattering occurs due to the presence of the dispersed particles, making colloids distinct from solutions.

Understanding this definition is key in differentiating colloids from other types of mixtures. For instance, a mixture of two immiscible liquids involves phases that do not mix at all, while a solution is composed of fully dissolved substances that appear homogeneous but do not retain the properties of their individual components. Likewise, a mixture of gases in a solid form does not reflect the essence of what constitutes a colloid.