( ( A ( chemical reaction ) ) ( ( is ( ( ( a change ) ( in matter ) ) ( ( in which ) ( ( different ( chemical substances ) ) ( are ( created ( by ( ( ( forming or ) breaking ) bonds ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT A) (NN chemical) (NN reaction)) (VP (VBZ is) (NP (NP (DT a) (NN change)) (PP (IN in) (NP (NN matter))) (SBAR (WHPP (IN in) (WHNP (WDT which))) (S (NP (JJ different) (NN chemical) (NNS substances)) (VP (VBP are) (VP (VBN created) (PP (IN by) (S (VP (VBG forming) (CC or) (VBG breaking) (NP (NNS bonds))))))))))) (. .)))
A chemical reaction is a change in matter in which different chemical substances are created by forming or breaking bonds.
(ROOT (S (NP (NNP Matter)) (VP (MD can) (RB not) (VP (VB be) (VP (VBN created) (CC or) (VBN destroyed) (PP (IN in) (NP (DT a) (NN chemical) (NN reaction)))))) (. .)))