evaporation of gasoline mixing salt and pepper dissolving sugar in tea rusting of an iron chain
I gave my students this multiple choice question: Which of these involves the formation of a new chemical substance?

Only one answer is correct among these 4 choices:
- evaporation of gasoline
- mixing salt and pepper
- dissolving sugar in tea
- rusting of an iron chain

Could you tell me which one is correct?

rusting of an iron chain