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?

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

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

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

To determine the correct conclusion, we need to analyze the information given. Johnny left a glass of milk on his bedside table for a week, and at the end of the week, the milk had changed. The glass contained a yellow liquid with lumpy white chunks, and there was a terrible odor.

Now let's evaluate the options:

A. The milk has undergone a physical change: A physical change refers to a change that does not alter the chemical composition of a substance. In this case, the milk has changed in color, consistency, and odor, indicating that a chemical reaction has occurred. Therefore, option A can be ruled out.

B. The mass of the milk before change is less than the mass of the milk after the change: The scenario does not provide any information about the mass of the milk before or after the change. Therefore, we cannot conclude that there is any change in mass. Option B is not supported by the information given.

C. Milk only forms ionic bonds: This statement is not related to the scenario and is not supported by any information. Option C is not valid.

D. The milk has undergone a chemical change: Based on the given information, such as the change in color, consistency, and odor, it can be concluded that a chemical change has occurred. The original milk has decomposed or spoiled, leading to the formation of new compounds with different properties. Hence, option D is the correct conclusion based on the available information.

The correct answer is D. The milk has undergone a chemical change.