Final answer:
Whole milk appears to be homogeneous but is revealed to be a colloid, a homogeneous mixture under normal observation, due to microscopic fat globules. Centrifugation or letting the milk stand shows that it is a heterogeneous mixture, as the fat separates from the water.
Step-by-step explanation:
To determine whether whole milk is a homogeneous or heterogeneous mixture, we can follow a simple procedure. First, examine the milk visually to see if it appears uniform. Since milk looks uniform to the nak_ed eye, one may initially classify it as homogeneous. However, to truly determine if a mixture is homogeneous or heterogeneous, it is necessary to look at the composition on a microscopic level.
Under a microscope, whole milk reveals tiny fat globules and protein particles dispersed in water, indicating it is not uniform throughout. Therefore, milk is a colloid, a type of homogeneous mixture with larger particles that do not settle out upon standing. Unlike solutions with particles the size of an ion or small molecule, colloids like milk have larger particles yet still appear uniform to the nak_ed eye.
To further this investigation, we can let the milk stand undisturbed and observe if any separation occurs. Milk that is left standing will eventually separate into cream and a more watery layer, demonstrating that it's a heterogeneous mixture. Another experiment could involve centrifugation, where the milk is rapidly spun, causing the denser fat particles to separate from the liquid, further proving the milk's heterogeneous nature. Filtration would not work for milk, as it would for a suspension, because the fat globules in milk are too small to be trapped by standard filters.