What makes milk a suspension?

A suspension is a heterogeneous mixture in which the solute particles are larger than 100 nm and can be seen with a microscope. The particles in a suspension are not soluble in the solvent and settle down over time. Examples of suspensions include sand in water, chalk in water, and gravel in water.

An emulsion is a heterogeneous mixture in which the solute particles are smaller than 100 nm and cannot be seen with a microscope. The particles in an emulsion are soluble in the solvent and do not settle down over time. Examples of emulsions include milk, mayonnaise, and salad dressing.

Milk is an emulsion because the fat particles in milk are smaller than 100 nm and cannot be seen with a microscope. The fat particles in milk are soluble in the water in milk and do not settle down over time.