▁to ▁the ▁mel ting ▁point . ▁The ▁mel ting ▁point ▁of ▁water ▁at ▁ 1 ▁atmosphere ▁of ▁pressure ▁is ▁very ▁close ▁to ▁ 0   ° C ▁( 3 2   ° F , ▁ 2 7 3 . 1 5   K ), ▁and ▁in ▁the ▁presence ▁of ▁nucle ating ▁subst ances ▁the ▁free zing ▁point ▁of ▁water ▁is ▁close ▁to ▁the ▁mel ting ▁point , ▁but ▁in ▁the ▁absence ▁of ▁nucle ators ▁water ▁can ▁super co ol ▁to ▁− 4 0   ° C ▁( − 4 0   ° F , ▁ 2 3 3   K ) ▁before ▁free zing . ▁Under ▁high ▁pressure ▁( 2 , 0 0 0 ▁atmos pher es ) ▁water ▁will ▁super co ol ▁to ▁as ▁low ▁as ▁− 7 0   ° C ▁( − 9 4   ° F , ▁ 2 0 3   K ) ▁before ▁free zing . ▁ ▁Ex oth erm icity ▁ ▁Free zing ▁is ▁almost ▁always ▁an ▁ex oth erm ic ▁process , ▁meaning ▁that ▁as ▁liquid ▁changes ▁into ▁solid , ▁heat ▁and ▁pressure ▁are ▁released . ▁This ▁is ▁often ▁seen ▁as ▁counter - int uit ive , ▁since ▁the ▁temperature ▁of ▁the ▁material ▁does ▁not ▁rise ▁during ▁free zing , ▁except ▁if ▁the ▁liquid ▁were ▁super co o led . ▁But ▁this ▁can ▁be ▁understood ▁since ▁heat ▁must ▁be ▁contin ually ▁removed ▁from ▁the ▁free zing ▁liquid ▁or ▁the ▁free zing ▁process ▁will ▁stop . ▁The ▁energy ▁released ▁upon ▁free zing ▁is ▁a ▁lat ent