( ( Phase changes ) ( require ( either ( ( ( ( ( the addition ) ( of ( heat energy ) ) ) ( -LRB- ( ( ( ( ( ( melting , ) evaporation ) , ) and ) sublimation ) -RRB- ) ) ) or ) ( subtraction ( of ( ( heat energy ) ( -LRB- ( ( ( ( condensation and ) freezing ) . ) -RRB- ) ) ) ) ) ) ) ) )
(ROOT (S (NP (NN Phase) (NNS changes)) (VP (VBP require) (NP (CC either) (NP (NP (DT the) (NN addition)) (PP (IN of) (NP (NN heat) (NN energy))) (PRN (-LRB- -LRB-) (NP (NP (NN melting)) (, ,) (NP (NN evaporation)) (, ,) (CC and) (NP (NN sublimation))) (-RRB- -RRB-))) (CC or) (NP (NP (NN subtraction)) (PP (IN of) (NP (NP (NN heat) (NN energy)) (PRN (-LRB- -LRB-) (NP (NP (NN condensation)) (CC and) (NP (NN freezing))) (. .) (-RRB- -RRB-)))))))))
Phase changes require       either the addition of heat energy (melting, evaporation, and sublimation)     or subtraction of heat energy (condensation and freezing.)
(ROOT (S (NP (NN Evaporation) (CC and) (NN condensation)) (VP (VBP are) (ADJP (JJ similar) (SBAR (IN because) (S (NP (DT both)) (VP (VBP are) (VP (VBN caused) (PP (IN by) (NP (NP (NNS changes)) (PP (IN in) (NP (NN heat) (NN energy))))))))))) (. .)))