What characteristic of colloids allows them to scatter light?

The characteristic of colloids that allows them to scatter light is primarily related to their larger particle size. Colloids consist of tiny particles that are intermediate in size between those found in true solutions and those found in suspensions, typically ranging from 1 nanometer to 1 micrometer. When light passes through a colloidal mixture, these larger particles can cause scattering due to their size compared to the wavelength of light.

The phenomenon of light scattering in colloids is known as the Tyndall effect. It occurs because the particles in a colloid are large enough to interact with and scatter light, making the beam of light visible as it passes through the colloidal solution. This characteristic distinguishes colloids from true solutions, where the solute particles are much smaller and do not scatter light in the same way.

Other options, such as solubility in water, ionic nature, and low density, do not have a direct relation to the scattering of light. While solubility and ionic nature can influence the stability and behavior of colloids in certain contexts, it is the particle size that directly leads to light scattering, which is the defining feature that enables us to observe this effect.