a change of state. a chemical reaction. the creation of matter. the movement of electricity.
I gave my students this multiple choice question: A student drops a white tablet into a glass of water, producing carbon dioxide gas. This is a demonstration of

Only one answer is correct among these 4 choices:
- a change of state.
- a chemical reaction.
- the creation of matter.
- the movement of electricity.

Could you tell me which one is correct?

a chemical reaction.