Johnny left a glass of milk on his bedside table for week, and it spoiled. At the end of the weel, the glass contained a yellow liquid with lumpy white chunks, and there was a terrible odor. What can be concluded?

Question

A. The milk has undergone a physical change
B. The mass of the milk before change is less than the mass of the milk after the change
C. Milk only forms ionic bonds
D. The milk has undergone a chemical change

Answer 1

Looks like it reacted chemically with something in the air to me :)

Answer 2

The milk has undergone a chemical change. Although A seems comprehendible, D is correct