( Elements ( ( are ( ( pure substances ) ( that ( ( can not ) ( be ( decomposed ( by ( chemical changes ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNS Elements)) (VP (VBP are) (NP (NP (JJ pure) (NNS substances)) (SBAR (WHNP (WDT that)) (S (VP (MD can) (RB not) (VP (VB be) (VP (VBN decomposed) (PP (IN by) (NP (NN chemical) (NNS changes)))))))))) (. .)))
Elements are pure substances that cannot be decomposed by chemical changes.
(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))))))))))) (. .)))