is a physical property. occurs when adding water to acid. is a sign of a chemical change. occurs when the water boils.
I gave my students this multiple choice question: One type of cold remedy is an effervescent tablet that breaks down in water. When the tablet is placed in water, it forms gas bubbles. In this example, the formation of a gas

Only one answer is correct among these 4 choices:
- is a physical property.
- occurs when adding water to acid.
- is a sign of a chemical change.
- occurs when the water boils.

Could you tell me which one is correct?

is a sign of a chemical change.