( Molecules ( ( ( combine ( through ( chemical reactions ) ) ) ( to ( form ( ( polymeric substances ) ( known ( as polymers ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNS Molecules)) (VP (VBP combine) (PP (IN through) (NP (NN chemical) (NNS reactions))) (S (VP (TO to) (VP (VB form) (NP (NP (JJ polymeric) (NNS substances)) (VP (VBN known) (PP (IN as) (NP (NNS polymers))))))))) (. .)))
Molecules combine through chemical reactions to form polymeric substances known as polymers.
(ROOT (S (NP (DT A) (NN combination) (NN reaction)) (VP (VBZ is) (NP (NP (DT a) (NN reaction)) (SBAR (WHPP (IN in) (WHNP (WDT which))) (S (NP (CD two) (CC or) (JJR more) (NNS substances)) (VP (VBP combine) (S (VP (TO to) (VP (VB form) (NP (DT a) (JJ single) (JJ new) (NN substance)))))))))) (. .)))