A 100-G Sample of a Certain Substance Undergoes a Transformation $\mathrm{J}$

A 100-g sample of a certain substance undergoes a transformation of some kind that releases 20,000 $\mathrm{J}$ of energy. What kind of transformation is this likely to be?

A) A temperature change
B) A phase change
C) A chemical reaction
D) A nuclear reaction
E) It is impossible to guess.