In which scenario is a chemical change occurring? a. a cup of ice cream is melting. b. a block of dry ice is sublimating. c. a section of iron fence is corroding. d. a flask of chlorine gas is condensing.

Answer is C because each of the above cause a change in state, hence it’s physical, the molecules remain same.
But corrosion is a chemical change, cause there is an addition of water and air to the regular iron molecules

The higher the temperature, the increased rate constant for a reaction.(positive linear association)