( ( ( A change ) ( in ( phase ( that takes ) ) ) ) ( ( place ( at ( a ( constant temperature ) ) ) ) . ) )
(ROOT (S (NP (NP (DT A) (NN change)) (PP (IN in) (NP (NP (NN phase)) (SBAR (WHNP (WDT that)) (S (VP (VBZ takes))))))) (VP (VBP place) (PP (IN at) (NP (DT a) (JJ constant) (NN temperature)))) (. .)))
A change in phase that takes place at a constant temperature.
(ROOT (S (PP (IN During) (NP (NN phase) (NN change))) (, ,) (NP (NP (DT the) (NN temperature)) (PP (IN of) (NP (DT a) (NN system)))) (VP (VBZ remains) (ADJP (JJ constant))) (. .)))