|MadSci Network: Chemistry|
Milk is both a "mechanical mixture" (in this case, called an "emulsion") and a solution.
The solution is a mixture of proteins (such as casein and whey proteins) and sugars (such as lactose) in water.
The emulsion, or mixture, is the milk fat suspended in the solution with the proteins as the "emulsifier" or stabilizer.
You can make your own emulsion by mixing 10 parts skim milk powder (dried proteins and sugars) with 100 parts water in a blender jar. Then add 4 parts vegetable oil (the "fat"). Blend or shake to make the oil be suspended in the water solution. The smaller the oil droplets become, the more stable the "emulsion".
This process of stabilizing the fat in solution is called "homogenization" in the dairy industry, and the milk is called "homogenized".
50 years ago, not all milk was homogenized, and the cream (fat) would separate and rise to the top of the milk bottles over time.
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