( ( An element ) ( ( is ( ( a ( pure substance ) ) ( which ( ( can not ) ( be ( ( split up ) ( by ( a ( chemical reaction ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT An) (NN element)) (VP (VBZ is) (NP (NP (DT a) (JJ pure) (NN substance)) (SBAR (WHNP (WDT which)) (S (VP (MD can) (RB not) (VP (VB be) (VP (VBN split) (PRT (RP up)) (PP (IN by) (NP (DT a) (NN chemical) (NN reaction)))))))))) (. .)))
An element is a pure substance which cannot be split up by a chemical reaction.
(ROOT (S (NP (PRP You)) (VP (VBP call) (NP (NP (DT a) (JJ pure) (NN substance)) (SBAR (WHNP (WDT that)) (S (VP (MD can) (RB not) (VP (VB be) (VP (VBN broken) (ADVP (RB down) (PP (IN into) (NP (NP (JJ different) (NNS types)) (PP (IN of) (NP (NNS substances)))))) (NP (DT a) (PRN (-LRB- -LRB-) (NP (NN n)) (-RRB- -RRB-)) (NN element))))))))) (. .)))