( ( Chemical reactions ) ( ( occur ( as ( elements ( rearrange ( to ( form ( new substances ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Chemical) (NNS reactions)) (VP (VBP occur) (SBAR (IN as) (S (NP (NNS elements)) (VP (VB rearrange) (S (VP (TO to) (VP (VB form) (NP (JJ new) (NNS substances))))))))) (. .)))
Chemical reactions occur as elements rearrange to form new substances.
(ROOT (S (NP (PRP You)) (VP (VBP call) (NP (NP (DT a) (NN substance)) (SBAR (WHNP (WDT that)) (S (VP (MD can) (RB not) (VP (VB be) (VP (VBN broken) (PRT (RP down)) (PP (TO to) (NP (JJ other) (NNS substances))) (PP (IN by) (NP (NP (NN chemical) (NNS reactions)) (NP (DT an) (NN element))))))))))) (. .)))