Answer:
Exothermic reaction
Explanation:
The phase change from liquid to solid by the freezing icicles is a typical exothermic reaction.
An exothermic process is one in which heat is lost to the surroundings.
To form the icicles, the dripping water must loose its heat to the environment. As the water cools below freezing point, the ice forms in form of the icicles observed.
Such reactions giving off heat is an exothermic reaction.