2. What is the first change that occurs when I2(s) is heated slowly at one atmosphere pressure?
(A) The solid melts.
(B) The solid vaporizes.
(C) The solid breaks into atoms.
(D) The solid becomes darker in color.
I do not understand why the answer is (B) and not (A), because on a phase diagram of iodine, if you increase temperature but keep pressure constant (at 1 atm) by going horizontally, the solid seems to melt first. What am I missing?