Milk is a natural emulsion. An emulsion is a mixture of two or more liquids that are normally immiscible (unmixable), such as oil and water. In an emulsion, one liquid is dispersed as small droplets throughout the other liquid. The droplets are stabilized by an emulsifier, which is a substance that prevents the droplets fromcoalescing (coming together). In milk, the emulsifier is a protein called casein. Casein is a globular protein that is found in milk in a soluble form. When milk is churned, the casein molecules are denatured (changed from their natural state) and form a network that traps the fat droplets. This network is what gives milk its white color and creamy texture.
A solution is a homogeneous mixture of two or more substances. The solute is the substance that is dissolved in the solvent. The solvent is the substance that does the dissolving. In a solution, the solute molecules are evenly distributed throughout the solvent molecules.
A mixture is a heterogeneous mixture of two or more substances. The components of a mixture are not evenly distributed throughout the mixture.
A suspension is a heterogeneous mixture of a solid and a liquid. The solid particles in a suspension are large enough to settle out of the liquid over time.
In conclusion, milk is a natural emulsion. It is a mixture of two immiscible liquids, fat and water, that are stabilized by an emulsifier, casein.