evaporation of gasoline mixing salt and pepper dissolving sugar in tea rusting of an iron chain
I am hesitating between 4 options to answer the following question, which option should I choose?
Question: Which of these involves the formation of a new chemical substance?
Possibilities:
- evaporation of gasoline
- mixing salt and pepper
- dissolving sugar in tea
- rusting of an iron chain

rusting of an iron chain