Which is an example of a colloid?

a) a mixture that settles out

b) a mixture that is separated by filtration

c) a mixture that scatters light

d) a salt and water mixture

the answer is c) a mixture that scatters light.

A mixture that scatters light is colloid

Explanation:

There are three categories of defining dissolution of a solute in a solvent:

a) true solution: where particle size is less than 1 nm

b) colloidal solutions: Where particles size is in between 1 - 1000 nm

c) suspension : where particle size is more than 1000 nm.

True solutions are homogeneous mixtures while colloids and suspensions are heterogeneous.

The mixture that settles out on standing is suspension. Example : sand in water.

A mixture that separated by filtration (normal filter paper) is again a suspension.

A mixture that scatters light is colloid. Colloids show tyndall effect.

A salt and water mixture is a true solution, which cannot be separated by filter paper or semi permeable membrane even.