Dry ice (solid CO2) sublimes directly to CO2 gas at room temperature and 1 atm. Which of the following provides the best justification for classifying this process as a physical change?
a) Because the sublimation can be reversed simply by cooling the gas back to a solid, its reversibility shows that it must be a physical change.
b) The process overcomes only intermolecular attractions between CO2 molecules; the covalent bonds within each molecule remain intact.
c) Sublimation absorbs energy from the surroundings, and the absorption of energy is characteristic of physical changes.
d) During sublimation the CO2 molecules briefly break apart into C atoms and O2 molecules that quickly recombine, so no overall chemical change is observed.