* Physical Change: A physical change alters the form or appearance of a substance but doesn't create a new substance. Mixing chocolate powder with milk is a physical change. You can still separate the chocolate from the milk (for example, by letting the milk settle and skimming off the chocolate powder).

* Chemical Change: A chemical change creates a new substance with different properties. Chocolate milk doesn't create a new chemical compound. The chocolate powder and milk are simply combined.

Therefore, chocolate milk is a mixture because it is a combination of two or more substances that are not chemically bonded. The chocolate powder and milk retain their individual properties.